Title of Invention

"A PROCESS OF MANUFACTURING FIBER REINFORCED PLASTIC ARTICLES USING FLEXIBLE MATERIAL PRESSURE MOULDING TECHNIQUE"

Abstract

The present invention relates to a process of preparing a fiber reinforced plastic (FRP) article comprising glass fiber and epoxy/polyester resin using a novel concept called rubber moulding technique, wherein the technique is based on matching die set, where the die is made of hard metal like steel and punch from flexible rubber like materials and uses a rubber punch, the said rubber punch applies hydrostatic pressure on the surface of the product. The novelty of the invention is to prepare complex shaped FRP articles without affecting the final FRP article. The split die and rubber punch are designed and fabricated to prepare complex shaped FRP article. The present invention also relates to a method for their preparation and its evaluation for structural applications through the measurement of inter laminar fracture toughness, inter laminar shear strength, tension strength, % of voids, % of fibers, etc. The present invention also discloses the rubber compound composition used for preparing the rubber punch and a method of preparing the said rubber punch.

Full Text

"A METHOD OF PREPARING FIBER REINFORCED PLASTIC ARTICLES USING RUBBER PRESSURE MOULDING TECHNIQUE" Field of the Invention The present invention relates to fiber reinforced plastic (FRP) article, a method for their preparation and its evaluation for structural applications through the measurement of inter laminar fracture toughness, inter laminar shear strength, tension strength, % of voids, % of fibers, etc. This technique is based on the matching die set, where the die is made from mild steel and the punch from flexible rubber material to apply pressure on the various surfaces of a complex shaped product. The novelty of the this invention is to prepare complex shaped FRP articles without affecting the final FRP article. Prior Art FRP articles (sometimes referred as components) have attracted increased attention over the past several years in a variety of fields including space craft, aerospace, automobile, civil, daily life, etc due to their light weight and very good mechanical properties. Such FRP articles have been prepared by pressure bag moulding, vacuum bag moulding, hand lay-up, spray up, hot press moulding, cold press moulding, etc. In these FRP articles, the fiber or fabric is distributed throughout the host matrix. Generally the host matrix is polyester/epoxy resin. But controlling the uniform distribution of fiber/fabric is difficult. Moreover the other disadvantages like microcracking of matrix, breaking of fibers, delamination, debonding, voids, etc. observed in the conventional fabrication technique is not desirable to improve the mechanical properties of FRP articles. The rubber mould through the utilization of hydrostatic pressure (developed during the compression of rubber mould) helps to reduce the microcracking of matrix, breaking of fibers, delamination, debonding, voids, etc in the FRP articles. But in order to produce high quality, high precession moulding for the aerospace industries, for example, it is necessary to have strict control over fiber alignment and consolidation of fiber in the matrix. Recently, there has been considerably interest in developing new process for the fabrication of FRP articles to improve the mechanical properties of the composite materials. To achieve this an autoclave moulding technique is used using prepreg, porous release material, bleeder material, nonporous release material, breather material and vacuum bag as shown in Figure 1. This type of approach, unfortunately, has limited usefulness. Indeed, a more direct, simple and economic approach to prepare FRP articles is highly desirable. Again the knowledge about fabrication of fiber reinforced plastic articles exited since 1970. However, the curing reaction, the effect of substrates on curing reaction, right grade of resin, curatives, and substrates are not known. As a result it was difficult to fabricate fiber reinforced plastic articles with strict quality control without using porous release material, bleeder material, nonporous release material, and breather material. (Figure Removed) Figure 1: Conventional process for fabrication of fiber reinforced plastic articles Development of new FRP articles having a minimum/free microcracking of matrix, breaking of fibers, delamination, debonding, voids, etc through out the matrix is desirable. Defects free FRP article provide a very good mechanical properties. In order to maintain its impact of composite materials and take the leadership in the world market of composite material, India has to break away from its traditional techniques to introduce new technology. Here a new technique is developed known as rubber pressure moulding. The potential benefits of such new technology are pervasive in technologies including space craft, automobile, aerospace, material and manufacturing, etc. However, past attempts to develop such process have been largely unsuccessful. Novelty The aerospace and automobile industries use costly bagging materials like porous release material, bleeder material, nonporous release material, breather material, flexible sheet and auto clave to fabricate fiber reinforced plastic articles. These bagging materials cannot be reused, which ultimately increases the cost of fiber reinforced plastic articles. Keeping this in mind, a new process has been developed, where we don't need to use porous release material, bleeder material, nonporous release material and breather material. Also the new technique does not require an autoclave, which is costly equipment. Even this new technology gives better mechanical properties than those of the conventional method. This new technology can also be used to produce a fiber reinforced plastic component (FRP) having complicated curved surface i.e., complex geometry. Objectives of the invention The main object of the invention is to develop a process for manufacturing fiber reinforced plastic articles (FRP) which overcome the disadvantages like microcracking of matrix, breaking of fibers, delamination, debonding, etc associated with conventional processes. Another object of the invention is to provide a process for manufacturing FRP products having complicated geometry. Another object of the invention is to provide a process for manufacturing FRP products using a metal die and a flexible rubber punch to fabricate FRP articles, which enables the application of nearly hydrostatic pressure on the article during curing of perform. Still another object of the invention is to adapt a new technique, named as the rubber pressure molding to fabricate fiber reinforced plastic (FRP) products from glass fiber fabric and polyester /epoxy resin Still another object of the invention is to provide a process for manufacturing flexible rubber punch for the production of FRP products. Summary of the Invention Accordingly the present invention provides a technique, named as the rubber pressure molding, has been developed to fabricate fiber reinforced plastic (FRP) products from glass fiber fabric and polyester /epoxy resin. The technique is based on matching die set, where the die is made from mild steel and the punch from flexible rubber material to apply pressure on the various surfaces of a complex shaped product. This new technique is successfully tested to fabricate FRP articles having complex geometry generally used for aerospace and automobile industries. A rubber punch die set (RPDS) is designed and fabricated to cast a rubber punch. The various rubber materials are tested to select appropriate materials. Five varieties of rubber materials i.e., natural rubber, butyl rubber, silicone rubber, styrene butadiene rubber and polybutadiene rubber are used to prepare rubber punch. Polyester resin does not cure with any of the natural rubber, silicone rubber and polybutadiene rubber, but partially cures in presence of styrene butadiene and butyl rubber. Epoxy resin cures well with natural rubber, butyl rubber, silicone rubber and styrene butadiene rubber. And it partially cures in presence of polybutadiene rubber. The present invention uses various types of coating agent are applied on the rubber surface to cure the polyester resin. These are polytetrafluoro ethylene, polyvinyl alcohol, silicone emulsion and soap solution. Using this new technique a FRP product named as flanged cone, is made from glass fiber using various rubber punches. The invention also provides composition used for preparing rubber punch, said composition includes, natural rubber, butyl rubber, silicone rubber, styrene butadiene rubber, polybutadiene rubber, zinc oxide, stearic acid, carbon black (GPF), paraffinic process oil, sulfur, mercaptobenzthiazole, BLN (antioxidant), and TMQ (antioxidant). Inter laminar fracture test, tension test and inter laminar shear test have been conducted on appropriately designed specimens to characterize the products fabricated by the rubber pressure molding technique and conventional process. The present invention also discloses, a comparison between the conventional process and rubber pressure moulding technique to evaluate its performance in target application. Brief description of accompanying drawings and tables Figure 1 shows the conventional process for fabrication of fiber reinforced plastic articles. Figure 2 is a SEM microphotograph of FRP composites prepared from glass fiber and polyester resin using rubber pressure moulding technique based on silicone rubber at a magnification of 3000 times. Figure 3 is a SEM microphotograph of FRP composites prepared from glass fiber and polyester resin using rubber pressure moulding technique based on butyl rubber at a magnification of 1700 times. Figure 4 is a SEM microphotograph of FRP composites prepared from glass fiber and polyester resin using rubber pressure moulding technique based on polybutadiene rubber at a magnification of 1500 times. Figure 5 shows the dimension of fiber reinforced plastic article having complex geometry Figure 6 shows the dimension of another fiber reinforced plastic article having complex geometry. Figure 7 shows the schematic diagram of rubber pressure moulding technique. Figure 8 shows the split steel die. Figure 9 shows the schematic diagram of rubber punch. Figure 10 shows the top part of the matching die. It is prepared from butyl rubber and called as butyl rubber punch (as a representative). Figure 11 shows the split steel die with styrene butadiene rubber punch and steel cone (as a representative). Figure 12 (A & B) shows the fiber reinforced plastic article prepared using this new technology. Here rubber punch is made of butyl rubber (as a representative). Figure 13 shows the variation of tensile strength of composite materials prepared from glass fiber and polyester resin made by conventional process and rubber pressure moulding technique using natural rubber at different black loading. Figure 14 shows the variation of inter laminar fracture toughness of composite materials prepared from glass fiber and polyester resin made by conventional process and rubber pressure moulding technique using natural rubber at different black loading. Figure 15 shows the variation of inter laminar shear strength of composite materials prepared from glass fiber and polyester resin made by conventional process and rubber pressure moulding technique using natural rubber at different black loading. Tables Table 1 shows the curing behavior of polyester resin on the surface of rubber chemicals. Table 2 shows the curing behavior of epoxy resin on the surface of rubber chemicals. Table 3 shows the curing behavior of polyester and epoxy resin on the surface of green rubber (without rubber chemicals). The substrates are green- natural rubber, polybutadiene rubber, styrene butadiene rubber, silicone rubber, natural rubber and butyl rubber (before curing). Table 4 shows the curing behavior of polyester and epoxy resin on the surface of green mixed rubber compounds (rubber chemicals are mixed with rubber, before curing). The substrates are mixed- natural rubber, polybutadiene rubber, styrene butadiene rubber, silicone rubber, natural rubber and butyl rubber (before curing). Table 5 shows the pressure and temperature used for the preparation of rubber punches, natural rubber, butyl rubber, silicon rubber, polybutadiene rubber and styrene butadiene rubber. Table 6 shows the curing behavior of polyester and epoxy resin on the surface of cured rubber. The substrates are natural rubber, polybutadiene rubber, styrene butadiene rubber, silicone rubber, natural rubber and butyl rubber. Table 7: shows the curing behavior of polyester and epoxy resin on the surface of coated rubber. The substrates are natural rubber, polybutadiene rubber, styrene butadiene rubber, silicone rubber, natural rubber and butyl rubber. The coating agents are polytetrafluoro ethylene (PTFE), polyvinyl alcohol (PVA), silicone emulsion solution and soap solution. Table 8 shows the formulations used for butyl rubber vulcanizates (in phr). Table 9 shows the formulations for natural rubber vulcanizates (in phr). Table 10 shows the formulations for styrene butadiene rubber vulcanizates (in phr). Table 11 shows the formulations for polybutadiene rubber vulcanizates (in phr). Table 12 shows the formulation for silicone rubber vulcanizates (in phr). Table 13 demonstrates the inter laminar fracture toughness tests of composite materials prepared from glass fiber and polyester resin. It is made by conventional method and rubber pressure moulding technique using butyl rubber (Vf = 0.4). The butyl rubber is coated with polyvinyl alcohol. Table 14 shows the inter laminar shear strength of specimens prepared from glass fiber and polyester resin. It is made by conventional method and rubber pressure moulding (Vf = 0.40) using butyl rubber. The butyl rubber is coated with polyvinyl alcohol. Table 15 shows the tensile strength, modulus of elasticity, % elongation and Poisson's ratio of specimens prepared from glass fiber and polyester resin. It is made by conventional method and rubber pressure moulding (Vf = 0.40) using butyl rubber and polyester resin. The butyl rubber is coated with polyvinyl alcohol. Table 16 shows mechanical properties of FRP laminates prepared from glass fiber and polyester resin. It is made by conventional method (Vf =0.45) and by rubber pressure molding technique using Natural rubber (Vf =0.47). The natural rubber surface is coated by polyvinyl alcohol. Table 17 shows inter laminar fracture toughness of composite materials prepared from glass fiber and polyester resin. It is made by conventional (Vf =0.49) and rubber pressure molding methods using Natural rubber (Vf = 0.52). The natural rubber surface is coated by polyvinyl alcohol. Table 18 shows inter laminar shear strength of composite materials prepared from glass fiber and polyester resin. It is made by Conventional (Vf = 0.53) and Rubber pressure molding methods using Natural rubber (Vf = 0.52). The natural rubber surface is coated by polyvinyl alcohol. Table 19 shows the differences between the fiber reinforced plastic article (Vf = 0.3) with respect to quality made of natural rubber and butyl rubber using epoxy resin and glass fiber. Table 20 shows the differences between the fiber reinforced plastic articles with respect to quality made by natural rubber and butyl rubber using polyester resin and glass fiber. Table 21 shows the differences between the fiber reinforced plastic article with respect to quality made of conventional process and rubber pressure moulding technique using butyl rubber, polyester resin and glass fiber. The butyl rubber is coated with polyvinyl alcohol. Table 22 shows the differences between the fiber reinforced plastic article with respect to quality made of polybutadiene and butyl rubber using polyester resin and glass fiber. Both rubbers are coated with polyvinyl alcohol. Table 23 shows the differences between the fiber reinforced plastic articles (Vf = 0.3) with respect to quality made of polybutadiene rubber and butyl rubber using epoxy resin and glass fiber. Table 24 shows the differences between the fiber reinforced plastic articles (Vf = 0.4) with respect to quality made by conventional process and rubber pressure molding technique using polybutadiene rubber in polyester matrix. Table 25 shows the differences with respect to quality of fiber reinforced plastic articles (Vf = 0.47) made of silicone rubber and butyl rubber using polyester resin and glass fiber. Both rubbers are coated with polyvinyl alcohol. Table 26 shows the differences with respect to quality of fiber reinforced plastic articles (Vf = 0.3) made of silicone rubber and butyl rubber in epoxy resin and glass fiber. Table 27 shows the differences with respect to quality of fiber reinforced plastic article made by conventional process and rubber pressure molding process using silicone rubber in polyester resin and glass fiber. Rubbers are coated with polyvinyl alcohol. Table 28 shows the mechanical properties of FRP laminates prepared from glass fiber and polyester resin. It is made by Conventional method and Rubber pressure molding technique with the help of Natural rubber with variation in carbon black content. The natural rubber surface is coated by polyvinyl alcohol. Table 29 shows inter laminar fracture toughness of composite materials prepared from glass fiber and polyester resin. It is made by Conventional (Vf =0.49) and Rubber pressure molding technique using Natural rubber with variation in carbon black content. Table 30 shows inter laminar shear strength of composite materials prepared from glass fiber and polyester resin. It is made by Conventional (Vf =0.49) and Rubber pressure molding technique using Natural rubber with variation in carbon black content Table 31 shows the fiber volume fraction including % of void in the product made of rubber pressure moulding technique using natural rubber, butyl rubber, silicone rubber, polybutadiene rubber and styrene butadiene rubber Detailed description of the invention: Accordingly, the present invention provides a process of manufacturing complex shaped fiber reinforced plastic (FRP) articles using rubber pressure moulding technique, said process comprising the steps of: a) cleaning the surfaces of the split steel die and flexible punch with a solvent; b) applying one or more coating agent selected from a group consisting of polytetrafluoro ethylene, polyvinyl alcohol, silicone emulsion and detergent/ soap solution on to the surface of the flexible punch, c) obtaining a perform comprising sandwiched glass fabric having appropriate shape carved out from a woven glass fibre sheet and a matrix of thermosetting polymer, d) placing the above perform on the flexible punch, e) then placing then the flexible punch with the perform in a split die, wherein the split die consisting of two or more pieces, f) bolting the split die using bolts till the two portion of the split die touches each other; g) loading the die, flexible punch with perform to lower platen of a hydraulic press and applying the hydraulic pressure for closing the die and allowing perform to cure at room temperature for about 16 hours; h) obtaining the cured product by loosing the bolt to open the split die and taking out the flexible punch; and i) repeating the above steps for continuously producing the FRP product. In an embodiment of the invention relates to a process of manufacturing FRP products, fiber used in reinforcing the plastic product is selected from group consisting of woven glass fabrics, glass mat (non woven), continuous fiber, etc. Another embodiment of the invention, wherein the thermosetting polymer used in manufacturing FRP is selected from a group consisting of polyester resin, epoxy resin, etc. Polyester resin (Parichem 3091) is selected from parichem 1012, parichem 1051, parichem 1091, parichem 2011, parichem 3021, parichem 3091, parichem 6011, etc. The catalyst used for the polyester resin is Parichem 350 and the accelerator for polyester resin used is Parichem 302. Epoxy resin used is selected from PH-800, PH-806, PH-807, PH-808, PH-809, PH-851, PH-853, PH-855, PH-856, PH-857, PH-858, PH-861, PH-866, PH-867, PH-870, PH-873, PH-874, PH-93, PH-96, PA-101, PA-102, PA-103, PG-100, PL-411, PG104, PC-311, PY-321, PC-351, PW-200, PG-321, PC-313 and PL-411, preferably PG-100. Hardener used is selected from PH-861, PH-851, PH-809, PH-853, PH-870, PH-866, PH-96, PH-855, PH-856, PH-861, PH-800, PH-857, PH-873 and PH-858, preferably PH-861. Another embodiment of the invention, the split die is made of either mild steel or carbon steel or carbon manganese steel or alloy steel or nickel-chromium hard chrome plating stainless steel The weight ratio of polyester resin, catalyst and accelerator is 100:2:2. The pressure cycle used in the hydraulic press is 0.4 MPa and the preform is allowed to cure at room temperature for 16 hours Another embodiment of the invention provides a flexible punch useful in FRP composite materials preparation, wherein the flexible punch is made up of a rubber compound. The rubber compound comprising a base rubber or combination of one or more rubber and other conventional rubber compounding ingredients such as reinforcing filler selected from carbon black, silica or combination thereof, metal oxide, fatty acid, process oil(s), vulcanizing agent(s), accelerator(s) and optionally one or more antioxidant, other conventional rubber compounding materials used in preparing rubber articles. The rubber used in preparing the rubber punch compound is selected from natural rubber, synthetic polyisoprene rubber, styrene-butadine rubber, polybutadine, isoprene-isobutlylene rubber (IIR or butyl rubber), silicone rubber, fluorocarbon rubber, polychloroprene rubber. The preferred rubber used for preparing the rubber punch is butyl rubber. The metal oxide is selected from zinc oxide, calcium oxide, magnesium oxide, lead oxide, etc which is in the range of 2 to 6 parts per hundred rubber (phr). The preferred metal oxide used is zinc oxide. The fatty acid used is selected from a group consisting of stearic acid, palmitic acid, oleic acid, etc which is in the range of 2 to 6 parts per hundred rubber (phr). The preferred fatty acid used is stearic acid. The reinforcing filler used is selected from one or more carbon black selected from group consisting of ISAF, HAF, FEF, GPF, SRF or other grades of commercially available carbon blacks which is in the range of 25 to 70 per hundred rubber (phr) and /or silica filler. The preferred reinforcing filler used is carbon black preferably GPF black. The process oil used is preferably low-staining or non-staining process oil either paraffinic oil or naphthenic oil or vegetable oil or combination thereof which is in the range of 2 to 10 parts per hundred rubber (phr) The preferred processing oil used is paraffinic oil. The antioxidant used is a amine type antioxidant either condensation product of acetone and diphenyl amine or phenyl-beta-napthylamine or blend of diphenyl-p-phenylene diamine and arylamine or blend of arylamines, or polymerized 1,2 dihydro 2,2,4- trimethyl quinoline or N-(l,3 -dimethylbutyl)-N'-phenyl-p-phenylene-diamine or diaryl para phenylene diamines or 2-mercapto benz imidazole or combination thereof which is in the range of 0 to 4 parts per hundred rubber (phr) The preferred antioxidants used are condensation product of acetone and diphenyl amine, and polymerized 1,2 dihydro 2,2,4- trimethyl quinoline The vulcanizing agent is selected from a group consisting of sulphur, phenol-formaldehyde resin (for resin curing of butyl rubber which has outstanding oxidation, heat and steam resistance), Zinc oxide (for chloroprene rubber) thereof which is in the range of 0.5 to 12 parts per hundred rubber (phr) The preferred vulcanizing agent used is sulfur and dicumyl per oxide. The accelerator used is selected from group consisting of tert-butylbenzthiazyl sulphenamide, 2-(4-morpholinyl mercapto)-benzthiazole, blend of thiazole and thiuram, dicyclohexyl benzthiazyl sulphenamide, blend of dithiocarbamates,. thiazole, cyclohexyl benzthiazyl sulphenamide, 2-mercaptobenzthiazole, dibenzthiazyl disulphide, tetramethylthiuram disulfide, zinc diethyl dithiocarbamate, zinc salt of mercaptobenzthiazole, 4-4' dithiodimorpholine, dicumyl peroxide thereof which is in the range of 0.5 to 6 parts per hundred rubber (phr). The preferred accelerators used are mercaptobenzthiazole and dicumyl peroxide. Further the rubber compound formulation optionally comprising tackifiers etc. The rubber compound is prepared by mixing the rubber and other compounding ingredients by conventional methods such as open mill mixing using two-roll mill and internal mixing using kneader, intermix and banbury mixer. The rubber punch is prepared by conventional methods such as compression moulding, transfer moulding and injection moulding by curing required quantity of the compounded rubber in a mould at a temperature in the range of 140 to 170°C using a hydraulic pressure of about 1 to 10 MPa for a period ranging between 10 to 100 minutes. A person skilled in the art can able to perform this activity without any difficulty. The optimum process conditions are i.e., temperature 150°C, pressure 5 MPa and time of about 25 minutes by evaluating mechanical properties of the vulcanizates. The weight ratio of polyester resin, catalyst (benzole peroxide) and hardener (methyl ethyl ketone) is 100:2:2 to make the FRP article using polyester resin. The weight ratio of epoxy resin and hardener (PH 861) is 100:10 to make the FRP article using epoxy resin. The FRP composite material is evaluated using Scanning electron microscopy micrograph of the fibers, which indicate that fibers are well distributed throughout the matrix (Figures 2, 3 and 4). Scanning electron microscopy micrograph is also used to see the interfacial bonding of the product using rubber pressure moulding technique. This is shown in Figures 2, 3 and 4. The bonding between matrix and fibers is good, indicating strong interfacial bonding and better load transfer from matrix to fibers (Figures 2, 3 and 4). In addition, the Scanning electron microscopy micrograph also indicates that there is no delamination in the product (Figures 2,3 and 4). Details of rubber and rubber chemicals used in the present invention Natural rubber (RMA IX) was obtained from Rubber Research Institute of India, Kerala. Since it was known that the molecular weight, molecular weight distribution and non-polymer constituent of natural rubber depend on the method of preparation, clonal variation of rubber tree and yield simultaneously, rubber from the same lot is used for the present investigation. Styrene-butadiene rubber (Synaprene 1502), a copolymer of styrene and butadiene, was supplied by Synthetic and Chemicals Ltd., Barely, U.P., India. It is non-staining grade. Polybutadiene rubber (Cisamer 1220) was supplied by Indian Petrochemicals Corporation limited. Silicone rubber was obtained from Dow corning, USA. Butyl rubber used is having about 2.0 % isoprene was obtained from Chemco Industry Corporation, Taiwan. General purpose furnace (GPF) was supplied by Philips Carbon black Ltd. Durgapur, India. Zinc oxide of chemically pure grade having about 98.0 ZnO content was obtained from M/s R.S. Agency, Calcutta, India. M/s Godrej Ltd., Bombay, India, supplied chemically pure grade stearic acid. Antioxidants used is Accinox TQ, TMQ (Polymerised 1,2 dihydro 2,2,4-trimethyl quinoline and BLN are obtained from ICI Ltd., Rishra, India. Paraffinic process oil are used and obtained from M/s Hindustan Petrochemical Ltd., Bombay, India. Rubber accelerator BSM [2-(4-morpholinyl mercapto)-benzthiazole] is used as accelerator and supplied by ICI Ltd., Rishra, India. Sulfur was of chemically pure grade, supplied by M/s Jain Chemicals, Kanpur, India. Glass fiber, polyester resin (Parichem 3091), epoxy resin (PG-100), catalyst (Parichem 350), accelerator (Parichem 302), hardener (PH-861) are supplied by Parikh Resins and Polymers Limited, India. Before making FRP articles it is necessary to check the curing properties of resins with the surface of the rubber mould for better surface finish and good quality of FRP products. Cured/uncured mixed rubber compound is a mixture of several rubber chemicals. To find out the behavior of the rubber chemicals with polyester/epoxy resin, all rubber chemicals like zinc oxide, stearic acid, carbon black (GPF), paraffinic process oil, sulfur, mercaptobenzthiazole, BLN (antioxidant), and TMQ (antioxidant) are poured separately into the mould cavity. The mould consists of 15 number of steel cylindrical tubes with an internal diameter of 35 mm, thickness of 3 mm and length of 15 mm. Polyester resin poured over the testing surface is mixed with the catalyst (benzole peroxide) and hardener (methyl ethyl ketone). The weight ratio of polyester resin, catalyst and hardener is 100:2:2. Similarly the epoxy resin is mixed with the hardener (PH 861) with a weight ratio of 100:10. The set up is kept at ambient temperature and pressure for 24 hours to check their curing behavior. The results are given in Tables 1 and 2. Both polyester and epoxy resin cures with zinc oxide, stearic acid, carbon black (GPF), paraffinic process oil, sulfur, mercaptobenzthiazole, BLN (antioxidant), and TMQ (antioxidant). Table 1: Curing behavior of polyester resin on the surface of rubber chemicals (Table Removed) Table 2: Curing behavior of epoxy resin on the surface of rubber chemicals (Table Removed) Then the raw rubbers are evaluated to understand the compatibility between polyester/epoxy resin and raw rubbers. The green rubbers (without rubber chemicals) are cut in the shape of a square of size 50 X 50 mm and kept in the mould used in the previous section. On the top of the surface, catalyst mixed polyester (The weight ratio of polyester resin, catalyst and hardener is 100:2:2.) and epoxy resin (The epoxy resin is mixed with the hardener (PH 861) with a weight ratio of 100:10) are poured. Similarly the set up is kept at ambient temperature and pressure for 24 hours to check their curing behavior. The results are given in Table 3. Epoxy resin perfectly cured with natural rubber, styrene butadiene rubber, silicone rubber, and butyl rubber; and partially cures with polybutadiene rubber. But polyester resin partially cures with styrene butadiene rubber and butyl rubber; and not cures with natural rubber, polybutadiene rubber and silicone rubber. Similarly the mixed uncured green rubber compounds (Raw rubber with other rubber chemicals) are also cut in the shape of a square of size 50 X 50 mm and kept in the mould used in the previous section. On the top of the surface, catalyst mixed polyester (The weight ratio of polyester resin, catalyst and hardener is 100:2:2.) and epoxy resin (The epoxy resin is mixed with the hardener (PH 861) with a weight ratio of 100:10) are poured. Similarly the set up is kept at ambient temperature and pressure for 24 hours to check their curing behavior. The results are given in Table 4. Epoxy resin perfectly cures with natural rubber, styrene butadiene rubber, silicone rubber, and butyl rubber; and partially cures with polybutadiene rubber. But polyester resin partially cures with styrene butadiene rubber and butyl rubber; and not cures with natural rubber, polybutadiene rubber and silicone rubber. Table 3: Curing behavior of polyester and epoxy resin on the surface of green rubber (without rubber chemicals). The substrates are green- natural rubber, polybutadiene rubber, styrene butadiene rubber, silicone rubber, natural rubber and butyl rubber (before curing) (Table Removed) Table 4 Curing behavior of polyester and epoxy resin on the surface of green mixed rubber compounds (rubber chemicals are mixed with rubber, before curing). The substrates are mixed-natural rubber, polybutadiene rubber, styrene butadiene rubber, silicone rubber, natural rubber and butyl rubber (before curing) (Table Removed) Now the mixed rubber compounds are cured over a range of temperature (140 to 170°C), pressure (1 to 10 MPa) and time (10 to 100 minutes) to find out optimum process conditions. The optimum process conditions are given in Table 5. It is evaluated through the measurement of mechanical properties of the vulcanizates. Table 5: Pressure and temperature used for the preparation of rubber punches, natural rubber, butyl rubber, silicon rubber, polybutadiene rubber and styrene butadiene rubber (Table Removed) Similarly the mixed cured rubber compounds are also cut in the shape of a square of size 50 X 50 mm and kept in the mould used in the previous section. On the top of the surface, catalyst mixed polyester (The weight ratio of polyester resin, catalyst and hardener is 100:2:2.) and epoxy resin (The epoxy resin is mixed with the hardener (PH 861) with a weight ratio of 100:10) are poured. Similarly the set up is kept at ambient temperature and pressure for 24 hours to check their curing behavior. The results are given in Table 6. Epoxy resin perfectly cures with natural rubber, styrene butadiene rubber, silicone rubber, and butyl rubber; and partially cures with polybutadiene rubber. But polyester resin partially cures with styrene butadiene rubber and butyl rubber; and not cures with natural rubber, polybutadiene rubber and silicone rubber. Table 6: Curing behavior of polyester and epoxy resin on the surface of cured rubber. The substrates are natural rubber, polybutadiene rubber, styrene butadiene rubber, silicone rubber, natural rubber and butyl rubber (Table Removed) To get a cure of polyester and epoxy resin on the rubber surface, four coating agents, namely, PTFE, PVA, Silicone emulsion and soap solution are applied on the surface. Similarly the coated cured rubber compounds are cut in the shape of a square of size 50 X 50 mm and kept in the mould used in the previous section. On the top of the surface, catalyst mixed polyester (The weight ratio of polyester resin, catalyst and hardener is 100:2:2.) and epoxy resin (The epoxy resin is mixed with the hardener (PH 861) with a weight ratio of 100:10) are poured. Similarly the set up is kept at ambient temperature and pressure for 24 hours to check their curing behavior. The results are given in Table 7. Polyester resin cures well in presence of natural rubber, poly butadiene rubber, styrene butadiene rubber and silicone rubber if PVA coating is applied on the rubber surface. It does not cure if no coating agent is used. Polyester resin also cures well with styrene butadiene rubber in presence of PTFE and silicone emulsion coatings. Epoxy resin cures well with all types of rubbers without any coating agent except poly butadiene rubber. Table 7: Curing behavior of polyester and epoxy resin on the surface of coated rubber. The substrates are natural rubber, polybutadiene rubber, styrene butadiene rubber, silicone rubber, natural rubber and butyl rubber. The coating agents are polytetrafluoro ethylene (PTFE), polyvinyl alcohol (PVA), silicone emulsion solution and soap solution (Table Removed) Butyl Rubber punch composition Rubber punches are prepared from butyl rubber containing zinc oxide, stearic acid, carbon black (GPF), paraffinic process oil, sulphur, and mercaptobenzthiazole. To find out optimum doses of all ingredients various formulations have been tried and preferred formulation is given in the following Table 8. Table 8: Formulations of butyl rubber vulcanizates (in phr) (Table Removed) Natural Rubber punch composition Rubber punches are prepared from natural rubber containing zinc oxide, stearic acid, carbon black (GPF), BLN (antioxidant), TMQ (antioxidant), paraffinic process oil, sulphur, and mercaptobenzthiazole. To find out optimum doses of all ingredients various formulations have been tried and preferred formulation is given in the following Table 9. Table 9: Formulations of natural rubber vulcanizates (in phr) (Table Removed) Styrene Butadine Rubber punch composition Rubber punches are prepared from styrene butadiene rubber containing zinc oxide, stearic acid, carbon black (GPF), BLN (antioxidant), TMQ (antioxidant), paraffinic process oil, sulphur, and mercaptobenzthiazole. To find out optimum doses of all ingredients various formulations have been tried and preferred formulation is given in the following Table 10. Table 10: Formulations of styrene butadiene rubber vulcanizates (in phr) (Table Removed) Polybutadine Rubber punch composition Rubber punches are prepared from polybutadiene rubber containing zinc oxide, stearic acid, carbon black (GPF), BLN (antioxidant), TMQ (antioxidant), paraffinic process oil, sulphur, and mercaptobenzthiazole. To find out optimum doses of all ingredients various formulations have been tried and preferred formulation is given in the following Table 11. Table 11: Formulations of polybutadiene rubber vulcanizates (in phr) (Table Removed) Silicone Rubber punch composition Rubber punch is prepared from silicone rubber containing dicumyl peroxide as a catalyst (Table 12). Table 12: Formulation of silicone rubber vulcanizates (in phr) (Table Removed) Butyl rubber punch Interlaminar fracture toughness of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using butyl rubber (Vf = 0.4) is better (470 J/m2) than conventional method (436 J/m2) (Table 13). Interlaminar shear strength of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using butyl rubber (Vf = 0.4) is better (40 MPa) than conventional method (30 MPa) (Table 14). Tensile strength of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using butyl rubber (Vf = 0.4) is comparable (338 MPa) with conventional method (342 MPa) (Table 15). Modulus of elasticity of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using butyl rubber (Vf = 0.4) is comparable (20 GPa) with conventional method (20 GPa) (Table 15). Elongation at breaking points of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using butyl rubber (Vf = 0.4) is comparable (2%) with conventional method (2%) (Table 15). Poisson's ratio of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using butyl rubber (Vf = 0.4) is comparable (0.19 MPa) with conventional method (0.19 MPa) (Table 15). Table 13: Inter laminar fracture toughness tests of composite materials (Table Removed) Table 14: Shear strength of composite materials (Table Removed) Table 15: Tensile strength, modulus of elasticity, % elongation and Poisson's ratio (Table Removed) Natural rubber punch Tensile strength of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using natural rubber (Vf = 0.47) is greater (328 MPa) than conventional method (Vf = 0.45) (300 MPa) (Table 16). Modulus of elasticity of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using natural rubber (Vf = 0.47) is greater (15.6 GPa) than conventional method (Vf = 0.45) (14.2 GPa) (Table 16). Elongation at breaking points of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using butyl rubber (Vf = 0.47) is comparable (4.3%) with conventional method (4.2%) (Vf = 0.45) (Table 16). Interlaminar fracture toughness of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using natural rubber (Vf = 0.52) is better (475 J/m2) than conventional method (424 J/m2) (Vf = 0.49) (Table 17). Interlaminar shear strength of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using natural rubber (Vf = 0.52) is better (19.6 MPa) than conventional method (18.5 MPa) (Vf = 0.53) (Table 18). Interlaminar fracture toughness of composite materials prepared from glass fiber and epoxy resin made by rubber pressure moulding technique using natural rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 166 J/m2, where as in case of butyl rubber under the same processing conditions is 208 J/m2 (Table 19). Interlaminar shear strength of composite materials prepared from glass fiber and epoxy resin made by rubber pressure moulding technique using natural rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 25 MPa, where as in case of butyl rubber under the same processing conditions is 59 MPa (Table 19). Tensile strength of composite materials prepared from glass fiber and epoxy resin made by rubber pressure moulding technique using natural rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 309 MPa, where as in case of butyl rubber under the same processing conditions is 346 MPa (Table 19). Modulus of elasticity of composite materials prepared from glass fiber and epoxy resin made by rubber pressure moulding technique using natural rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 20 MPa, where as in case of butyl rubber under the same processing conditions is 21 MPa (Table 19). Elongation at breaking point of composite materials prepared from glass fiber and epoxy resin made by rubber pressure moulding technique using natural rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 2.0%, where as in case of butyl rubber under the same processing conditions is 2.2% (Table 19). It is not possible to fabricate FRP products using natural rubber and polyester resin. This is due to the curing problem. But it is possible to fabricate a FRP product using natural rubber and polyester resin (Table 20). Table 16: Tensile strength, modulus of elasticity, % elongation and Poisson's ratio (Table Removed) Table 17: Inter laminar fracture toughness (Table Removed) Table 18: Inter laminar shear strength (Table Removed) Table 19: Comparison of FRP products made by natural rubber and butyl rubber (Table Removed) Table 20: Comparison of FRP products made by natural rubber and butyl rubber (Table Removed) Comparison of physical properties of FRP products prepared by conventional methods and rubber pressure moulding technique Interlaminar fracture toughness of composite materials prepared from glass fiber and polyester resin made by conventional process is 435 J/m2, where as in case of rubber pressure moulding technique using butyl rubber under the same processing conditions is 470J/m2 (Table 21). Interlaminar shear strength of composite materials prepared from glass fiber and polyester resin made by conventional process is 30 MPa, where as in case of rubber pressure moulding technique using butyl rubber under the same processing conditions is 40 MPa (Table 21). Tensile strength of composite materials prepared from glass fiber and polyester resin made by conventional process 340 MPa, where as in case of rubber pressure moulding technique using butyl rubber under the same processing conditions is 338 MPa (Table 21). Modulus of elasticity of composite materials prepared from glass fiber and polyester resin made by conventional process is 20 MPa, where as in case of rubber pressure moulding technique using butyl rubber under the same processing conditions is 20 MPa (Table 21). Elongation at breaking point of composite materials prepared from glass fiber and polyester resin made by conventional process is 2.0%, where as in case of rubber pressure moulding technique using butyl rubber under the same processing conditions is 2.0% (Table 21). Poisson's ratio of composite materials prepared from glass fiber and epoxy resin made by conventional process is 0.2, where as in case of rubber pressure moulding technique using butyl rubber under the same processing conditions is 0.2 (Table 21). Table 21: Comparison of FRP products (Vt = 0.4) made by conventional process and rubber pressure moulding technique using butyl rubber and polyester resin (Table Removed) Polybutadine rubber punch Interlaminar fracture toughness of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using polybutadiene rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 450 J/m2, where as in case of butyl rubber under the same processing conditions is 470J/m (Table 22). Interlaminar shear strength of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using polybutadiene rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 37 MPa, where as in case of butyl rubber under the same processing conditions is 40 MPa (Table 22). Tensile strength of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using polybutadiene rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 330 MPa, where as in case of butyl rubber under the same processing conditions is 338 MPa (Table 22). Modulus of elasticity of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using polybutadiene rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 18 MPa, where as in case of butyl rubber under the same processing conditions is 20 MPa (Table 22). Elongation at breaking point of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using polybutadiene rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 2.0% , where as in case of butyl rubber under the same processing conditions is 2.0% (Table 22). Poisson's ratio of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using polybutadiene rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 0.2, where as in case of butyl rubber under the same processing conditions is 0.2 (Table 22). Interlaminar fracture toughness of composite materials prepared from glass fiber and epoxy resin made by rubber pressure moulding technique using polybutadiene rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 175 J/m2, where as in case of butyl rubber under the same processing conditions is 208 J/m (Table 23). Interlaminar shear strength of composite materials prepared from glass fiber and epoxy resin made by rubber pressure moulding technique using polybutadiene rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 44 MPa, where as in case of butyl rubber under the same processing conditions is 59 MPa (Table 23). Tensile strength of composite materials prepared from glass fiber and epoxy resin made by rubber pressure moulding technique using polybutadiene rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 338 MPa, where as in case of butyl rubber under the same processing conditions is 346 MPa (Table 23). Modulus of elasticity of composite materials prepared from glass fiber and epoxy resin made by rubber pressure moulding technique using polybutadiene rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 19.5 MPa, where as in case of butyl rubber under the same processing conditions is 20.9 MPa (Table 23). Elongation at breaking point of composite materials prepared from glass fiber and epoxy resin made by rubber pressure moulding technique using polybutadiene rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 2.1%, where as in case of butyl rubber under the same processing conditions is 2.2% (Table 23). Interlaminar fracture toughness of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using polybutadiene rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 450 J/m2, where as in case of conventional method under the same processing conditions is 435 J/m2 (Table 23). Interlaminar shear strength of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using polybutadiene rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 37 MPa J/m2, where as in case of conventional method under the same processing conditions is 30 MPa (Table 24). Tensile strength of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using polybutadiene rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 330 MPa, where as in case of conventional method under the same processing conditions is 340 MPa (Table 24). Modulus of elasticity of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using polybutadiene rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 18 GPa, where as in case of conventional method under the same processing conditions is 20 GPa (Table 24). Elongation at break of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using polybutadiene rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 2%, where as in case of conventional method under the same processing conditions is 2% (Table 24). Poisson's ratio of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using polybutadiene rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 0.19, where as in case of conventional method under the same processing conditions is 0.19 (Table 24). Table 22 Comparison of FRP products (Vf = 0.4) made by rubber pressure moulding technique using polybutadiene rubber and butyl rubber in polyester matrix (Table Removed) Table 23: Comparison of FRP products made by rubber pressure moulding technique using polybutadiene rubber and butyl rubber in epoxy matrix (Table Removed) Table 24: Comparison of FRP products made by rubber pressure moulding technique using polybutadiene rubber and conventional process in polyester matrix (Table Removed) Butyl rubber punch Interlaminar fracture toughness of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using butyl rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 470 J/m2, where as in case of silicone rubber under the same processing conditions is 490 J/m2 (Table 25). Interlaminar shear strength of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using butyl rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 40 MPa J/m2, where as in case of silicone rubber under the same processing conditions is 60 MPa (Table 25). Tensile strength of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using butyl rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 338 MPa, where as in case of silicone rubber under the same processing conditions is 360 MPa (Table 25). Modulus of elasticity of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using butyl rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 20 GPa, where as in case of silicone rubber under the same processing conditions is 22 GPa (Table 25). Elongation at break of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using butyl rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 2%, where as in case of silicone rubber under the same processing conditions is 2% (Table 25). Poisson's ratio of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using butyl rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 0.19, where as in case of silicone under the same processing conditions is 0.19 (Table 25). Interlaminar fracture toughness of composite materials prepared from glass fiber and epoxy resin made by rubber pressure moulding technique using butyl rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 208 J/m2, where as in case of silicone rubber under the same processing conditions is 205 J/m2 (Table 26). Interlaminar shear strength of composite materials prepared from glass fiber and epoxy resin made by rubber pressure moulding technique using butyl rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 59 MPa J/m , where as in case of silicone rubber under the same processing conditions is 55 MPa (Table 26). Tensile strength of composite materials prepared from glass fiber and epoxy resin made by rubber pressure moulding technique using butyl rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 346 MPa, where as in case of silicone rubber under the same processing conditions is 342 MPa (Table 26). Modulus of elasticity of composite materials prepared from glass fiber and epoxy resin made by rubber pressure moulding technique using butyl rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 21 GPa, where as in case of silicone rubber under the same processing conditions is 21 GPa (Table 26). Elongation at break of composite materials prepared from glass fiber and epoxy resin made by rubber pressure moulding technique using butyl rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 2.2%, where as in case of silicone rubber under the same processing conditions is 2.1% (Table 26). Table 25: Comparison of FRP products made by rubber pressure moulding technique using butyl rubber and silicone rubber in polyester matrix, (Table Removed) Table 26: Comparison of FRP products made by rubber pressure moulding technique using butyl rubber and silicone rubber in epoxy matrix (Table Removed) Silicone rubber punch Pnterlaminar fracture toughness of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using silicone rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 490 J/m2, where as in case of conventional method under the same processing conditions is 435 J/m2 (Table 27). Interlaminar shear strength of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using silicone rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 60 MPa, where as in case of conventional method under the same processing conditions is 30 MPa (Table 27). Tensile strength of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using silicone rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 360 MPa, where as in case of conventional method under the same processing conditions is 340 MPa (Table 27). Modulus of elasticity of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using silicone rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 22 GPa, where as in case of conventional method under the same processing conditions is 20 GPa (Table 27). Elongation at break of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using silicone rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 2%, where as in case of conventional method under the same processing conditions is 2% (Table 27). Poisson's ratio of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using silicone rubber containing 50 phr (per hundred rubber) carbon black (GPF) is 0.19, where as in case of conventional method under the same processing conditions is 0.19 (Table 27). Table 27: Comparison of FRP products made by conventional process and rubber pressure moulding technique using silicone rubber in polyester matrix (Table Removed) Natural rubber punch Tensile strength of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using natural rubber with 0 to 75 phr carbon black (GPF) as reinforcing filler is in the range of 294 to 353 MPa where as in case of conventional method under the same processing conditions is 14.2 GPa (Table 28). Modulus of elasticity of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using natural rubber with 0 to 75 phr carbon black (GPF) as reinforcing filler is in the range of 14.8 - 18.1 GPa where as in case of conventional method under the same processing conditions is 14.2 GPa (Table 28). Volume fraction of fibers of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using natural rubber with reinforcing filler carbon black (GPF) in the range of 0 to 75 phr is in the range of 52 -57.1 % where as in case of conventional method under the same processing conditions is 45% (Table 28). Void content of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using natural rubber natural rubber containing carbon black (GPF) in the range of 0 to 75 phr is in the range of 1.7 to 2.6% where as in case of conventional method under the same processing conditions is 2.7% (Table 28). Interlaminar fracture toughness of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using natural rubber with reinforcing filler (carbon black, GPF) in the range of 0 to 70 phr is in the range of 386 to 476 J/m2 when compared to conventional method under the same processing conditions which is 424 J/m2 (Table 29). Interlaminar shear strength of composite materials prepared from glass fiber and polyester resin made by rubber pressure moulding technique using natural rubber with reinforcing filler (carbon black, GPF) in the range of 0 to 70 phr is in the range of 11 MPa to 17 when compared to conventional method under the same processing conditions which is 18.5 MPa (Table 30). Table 28: Mechanical properties of FRP laminates prepared from glass fiber and polyester resin made by Conventional method and by Rubber pressure molding technique using Natural rubber with variation in carbon black content. The natural rubber surface is coated by polyvinyl alcohol. (Table Removed) Table 29: Inter laminar fracture toughness of composite materials (Table Removed) Table 30: Inter laminar shear strength, volume fraction of fiber and void content of composite Materials (Table Removed) Examples Preparation of FRP composite using butyl rubber punch 1. 18.5 gm zinc oxide, 7.4 gm stearic acid, 185 gm carbon black (GPF), 18.5 gm paraffinic process oil, 11.1 gm sulfur and 7.4 gm mercaptobenzthiazole are mixed in 370 gm butyl rubber at a temperature of 70°C, mixing time of 40 minutes and friction ratio of 1:1.1 in a two roll mixing mill. The split steel die is preheated before putting mixed rubber in it. The preheating is done in a hydraulic press at a temperature of 160°C. After temperature is reached close to 160°C, uncured rubber is filled in the die and the steel cone is placed over it. A nut and bolt system is placed inside the rubber punch for easy removal of the article from the rubber punch after curing of preform. The pressure is 5 MPa. The temperature and pressure is maintained for 30 minutes. The cured rubber punch is taken out by removing bolts on the metal plate of die. Now a hand lay-up technique is used to prepare the preform (uncured form of product). The glass fabric is cut in right shape using the template 1 from a woven glass fiber sheet. The template is designed in such way that the uncut portion covers cylindrical portion of the product and the cut portion covers the conical and base portion of the product. The conical and base of the product does not give continuous laying, so template 2 and template 3 are inserted in conical and base portion after every two layers of template 1. The matrix used to prepare the product is epoxy/polyester resin. The epoxy resin is mixed with 10% of hardener (PH861) to cure the resin. The weight ratio of polyester resin, catalyst (benzole peroxide) and hardener (methyl ethyl ketone) is 100:2:2 to make the FRP article using polyester resin. Total numbers of template 1, template 2 and template 3 used to prepare the preform are 4, 2, and 2 respectively. Coating agent like polytetrafluoro ethylene/ polyvinyl alcohol/ silicone emulsion/ soap solution is applied on the rubber punch. Using hand lay-up technique the glass fabric and the catalyst mixed epoxy/polyester resin are placed on the coated rubber punch, then the rubber punch with preform is placed inside the split steel die and four bolts of the die set is bolted till the two portion of the split die touches each other. Then, steel cone is placed over the rubber punch. The steel die and the rubber punch with preform are loaded in a hydraulic press. The pressure cycle used in the hydraulic press is 0.4 MPa and the preform is allowed to cure at room temperature for 16 hours. The steel die is separated in to two parts by removing the bolts after curing of preform. To take out the product from the rubber punch, a Ml2 bolt is placed on the Ml2 nut inside the rubber punch and screwed slowly to take out the product from the rubber punch. The purpose of placing the nut and a steel plate inside the rubber punch to take out the product easily with out hammering the rubber and the FRP product. Burn test, coin test, scanning electron microscopy (SEM) and mechanical tests like interlaminar fracture toughness, inter laminar shear test, tension test, etc are carried out to know the void content, presence of delamination, bonding between fiber and resin, microstructure and performance of the composite materials. Coin Test: This test gives an idea of delamination in the FRP products. The delamination is checked while tapping a coin on the FRP product. If the sound is like that of a metal i.e., high frequency, it ensures the good quality of product. Otherwise delamination or high void content may be present in the product. The coin test in the FRP product (pump cap) is found to be high frequency in all the three parts (cylindrical, conical, and flat surface). Burn Test: In burn test, volume fraction of the fiber, matrix and void contents are calculated. This test has been conducted for cylindrical, conical and flat part of the FRP pump cap. Procedure to conduct the burn test is as follows: (1) A specimen of size 10X10 mm is cut from the product. (2) The specimen is cleaned and dried to remove unwanted material from the specimen, and then the specimen is weighted in air and water to determine the specific gravity of the composite materials. (3) It is kept in a furnace and the furnace temperature is gradually increased to 1000°C to burn out resin completely. It is hold at 1000°C for 20 minutes and furnace is switched off. The residue is taken out, when it is cooled to room temperature and its weight is taken, which gives the weight of the fiber. The volume fractions of fiber, matrix and void content in the specimens are calculated from the specific gravity of the composite specimen, weight of the fiber, density of resin and density of fiber. The following equations are used to determine volume fraction of fiber and void content in the composite specimen. Density of the composite specimen, pc is given by where, pw, ma and mw are density of water, weight of specimen in air and weight of the specimen in water respectively. Weight of the fiber (mf) and the matrix (mm) are obtained after burning the specimen. Volume fraction of the fiber (Vf) and void content (Vv) are given by (Equation Removed) where, Pf pct and pce are density of the fiber, theoretical and experimental density of the specimen respectively. Theoretical density of composite is given by (Equation Removed) Five specimens are cut from each sections of pump cap, i.e. cylindrical, conical and flat surfaces and burn test is conducted to find out volume fraction of fiber and void contents. Scanning Electron Microscopy: Studies for wetting characteristics, delamination and fiber matrix interaction are done by JSM-840 Scanning Electron microscope, JEOL, JAPAN. The specimens of size 10X10 mm are cut from the product and the edges having fiber cross-section are smoothened by a waterproof emery paper. Then, the edge is polished by a powder, 0.3 micron alpha alumina. Inter laminar Fracture Toughness: The double cantilever beam (DCB) specimen is prepared by 12 layers of bi-directional glass fiber. The thickness of laminate is 4 mm. A precarck is introduced in the laminate by inserting a thin sheet of BOPP (biaxially oriented polypropylene) film at the mid plane of the laminate during the stacking of glass fiber fabric. The BOPP film is kept at one end in the mid plane during the fabrication of the specimen. The laminate is kept for 16 hours at a temperature of 25°C and pressure of 0.5 MPa to get cure. After the laminate is prepared, it is cut to the specified size of the specimen for testing. The dimensions of the specimen are given as, Length, L = 200 mm; Precrack length, ao = 40 mm; Width, b= 30 mm; and Thickness, 2h= 4 mm. The ends of the specimen are prepared in such a way that they can be fixed to the loading fixture. The loading fixture consists of top and bottom rectangular tabs, which are fitted to the specimen with the help of bolts. The tabs are tightened by the bolt from opposite side of the tabs such that the bolts only touches the respective tabs not other one. The specimen is painted with white color on the both side along thickness to mark the crack tip accurately during the experiment. A thin strip from a graph sheet is bonded on the top of the specimen to measure the crack length for the measurement of inter laminar facture toughness. The top and bottom rectangular tabs are hold by the jaw of the Instron machine and properly aligned. The specimen is tested in the tensile mode with a crosshead speed of 1 mm/min. The load cell with maximum capacity of 100 kN is used and the load range is set to 0.2 kN. The chart speed set to 10 mm/min. A real time display of load vs. deflection is obtained. During loading, when a sudden change in the slope of the loading curve is observed. The machine is then stopped and waits for some time for the crack to self arrest. Then the exact crack tip portion is marked on the specimen on both side of the specimen. To locate exact point of crack tip, a magnifying lens is used. The specimen is unloaded and the machine is stopped at zero load. The machine is reloaded to get the similar plot for the next crack length. The experiment is repeated for 5-6 times. The critical load Pco, Pc1 Pen for corresponding crack length of ao, ai_ a„ are measured. The first cycle is excluded from the calculation as cantilevers are partially bonded to the BOPP precarck and they are not free to move. Inter laminar fracture toughness is determined by using the following expression where A1 and A2 are constants for a given specimen and b is the width of specimen. A1 and A2 can be evaluated from experimental data obtained from DCB test and using an approximate data reduction technique. Inter laminar Shear Test: The specimens are made of 6 layers of glass fiber fabric/epoxy resin in order to get 2 mm thick sheet. After the lamina is prepared, it is cut with the help of diamond cutter to the dimension of 20 mm long, 10 mm wide and 2 mm thick. Five specimens are cut from single laminate. The test has been conducted on the specimens with 0° orientation of warp fibers along loading direction. The tests are carried out on MTS-810 machine. The specimen is placed on the base plate and aligned. The tests are conducted in the displacement control mode with a loading rate of 2 mm/min. The load is applied with the center load wedge. The inter laminar shear strength is calculated from the load vs. displacement graph with the help of the following equation (Equation Removed) where F, b and d are the applied load, width and the depth of the specimen section respectively. Tension Test: The width, length and the thickness of the specimen are 25, 175 and 2.5 mm respectively. The length, width and thickness of end tabs are 30, 25 and 2 mm respectively. To prepare specimen with 0° orientation along loading direction and 2.7 mm thickness 8 layers of bidirectional glass fiber are used. After the preparation of the laminate in conventional and rubber molding techniques, the laminates are cut to the specified dimension using diamond impregnated wheel cutter. The end tabs used in the specimen with thickness of 2 mm are prepared from 6 layers of bidirectional glass fiber fabric and epoxy resin. The end tabs are cut from these laminates to the required geometry. Then the end tabs are bonded to the specimen using epoxy resin. After bonding the end tabs, specimens are marked at the center of the specimen to place the extensometer. The specimen is clamped in the hydraulic wedge grip of the MTS-810 machine up to the depth of 30 mm from both ends. The proper alignment of the specimen in the jaw is assured as minor change in the direction of pull gives an incorrect value. The extensometer with 50 mm gauge length is placed at the center of the specimen. The tests are conducted in displacement control mode with loading rate of 1 mm/min. The applied load is measured with the help of load cell and strain is measured with the help of extensometer. A typical load vs strain graph is obtained from the plotter of the MTS machine. Tensile strength, modulus of elasticity in longitudinal direction and the percentage of elongation are calculated from this graph. The slope of the graph is linear initially but as load on the specimen increases the fiber starts breaking and the curve becomes non-linear. The slope of the linear curve is used to calculate the modulus of elasticity. The tests are conducted on 5 specimens prepared by each technique. Preparation of FRP composite material using silicone rubber punch 2. 65 gm dicumyl peroxide is mixed in 650 gm silicone rubber at a temperature of 70°C, mixing time of 15 minutes and friction ratio of 1:1.1 in a two roll mixing mill. The uncured mixed silicone rubber is filled in the die and the steel cone is placed over it at a temperature of 160°C. The pressure is 5 MPa. The temperature and pressure is maintained for 30 minutes. The cured rubber punch is taken out by removing bolts on the metal plate of die. Now again hand lay-up technique is used to prepare the preform (uncured form of product). The glass fabric is cut in right shape using the templates 1, 2 and 3 from a woven glass fiber sheet. The matrix used to prepare the product is epoxy/polyester resin. The epoxy resin is mixed with 10% of hardener (PH861) to cure the resin. The weight ratio of polyester resin, catalyst (benzole peroxide) and hardener (methyl ethyl ketone) is 100:2:2 to make the FRP article using polyester resin. Total numbers of template 1, template 2 and template 3 used to prepare the preform are 6, 3, and 3 respectively. Polyvinyl alcohol coating agent is applied on the rubber punch to make a FRP article using polyester resin. Other wise polytetrafluoro ethylene /silicone emulsion is applied on the rubber punch to make a FRP article using epoxy resin. Using hand lay-up technique the glass fabric and the catalyst mixed epoxy/polyester resin are placed on the coated rubber punch, then the rubber punch with preform is placed inside the split steel die and four bolts of the die set is bolted till the two portion of the split die touches each other. Then, steel cone is placed over the rubber punch. The steel die and the rubber punch with preform are loaded in a hydraulic press and allowed to cure at room temperature for 16 hours. Now the FRP product made of rubber pressure moulding technique using silicone rubber is characterized by burn test, coin test, scanning electron microscopy (SEM) and mechanical tests like interlaminar fracture toughness, inter laminar shear test, tension test, etc (methods described above). Preparation of FRP composite material using natural rubber punch 3. 21.25 gm zinc oxide, 12.75 gm stearic acid, 8.5 gm BLN (antioxidant), 8.5 gm TMQ (antioxidant), 212.5 gm carbon black (GPF), 21.25 gm paraffmic process oil, 12.75 gm sulfur and 8.5 gm mercaptobenzthiazole are mixed in 425 gm natural rubber at a temperature of 70°C, mixing time of 40 minutes and friction ratio of 1:1.1 in a two roll mixing mill. The uncured mixed natural rubber is filled in the die and the steel cone is placed over it at a temperature of 150°C and pressure of 5 MPa. The temperature and pressure is maintained for 30 minutes. The cured rubber punch is taken out by removing bolts on the metal plate of die. Now again hand lay-up technique is used to prepare the preform (uncured form of product). The glass fabric is cut in right shape using the templates 1, 2 and 3 from a woven glass fiber sheet. The matrix used to prepare the product is epoxy/polyester resin. The epoxy resin is mixed with 10% of hardener (PH861) to cure the resin. The weight ratio of polyester resin, catalyst (benzole peroxide) and hardener (methyl ethyl ketone) is 100:2:2 to make the FRP article using polyester resin. Total numbers of template 1, template 2 and template 3 used to prepare the preform are 6, 3, and 3 respectively. Polyvinyl alcohol coating agent is applied on the rubber punch to make a FRP article using polyester resin. Other wise polytetrafluoro ethylene/ polyvinyl alcohol/ silicone emulsion/ soap solution is applied on the rubber punch to make a FRP article using epoxy resin. Using hand lay-up technique the glass fabric and the catalyst mixed epoxy/polyester resin are placed on the coated rubber punch, then the rubber punch with preform is placed inside the split steel die and four bolts of the die set is bolted till the two portion of the split die touches each other. Then, steel cone is placed over the rubber punch. The steel die and the rubber punch with preform are loaded in a hydraulic press and allowed to cure at room temperature for 16 hours. Now the FRP product made of rubber pressure moulding technique using natural rubber is characterized by burn test, coin test, scanning electron microscopy (SEM) and mechanical tests like interlaminar fracture toughness, inter laminar shear test, tension test, etc are carried out to know the void content, presence of delamination, bonding between fiber and resin, microstructure and performance of the composite materials (methods described above). Example: Preparation of complex shaped FRP composite material The complex shaped product, pump cap (Figure 5) has been chosen to make from FRP using rubber pressure molding technique. The pump cap selected in this study, which is a component of cooler pump, is usually made of steel sheet of thickness 1 mm. It usually gets rusted and it was felt that a component of composite pump might be a more appropriate material. This component has three important geometry elements (i) cylindrical, (ii) conical and (iii) flat surface (Figure 5). The cylindrical part has an outer diameter of 120 mm and thickness of 1.5 mm; the conical portion has a half cone angle of 45° and thickness of 1.5 mm; the flat portion has a diameter of 70 mm and thickness of 1.5 mm. The total height of the pump cap is 75 mm. Another complex shaped product (Figure 6) is also made using this rubber pressure moulding technique. To prepare the pump cap (Figure 5) from FRP a split steel die, steel cone and flexible rubber punch are used. A schematic diagram of the overall setup is shown in Figure 7. Split steel die has an interior conforming to an external shape of the component. The die is made in two parts for easy removal of component once it is cured. A perform of glass fiber fabrics wetted with epoxy/polyester resin is placed in between split die and rubber punch as shown in Figure 7. Then the rubber punch is pressed by a suitably designed steel cone. A force on the steel cone is applied by the hydraulic press. The product is cured in 16 hours at room temperature and pressure of 0.4 MPa. The material for the die chosen is mild steel as mild steel has high strength, good macinability, good thermal conductivity, high stiffness and good compressive strength. Thus the material is suitable to bear high compressive stresses developed during the curing of performs under pressure. The same die is also used to prepare rubber punch. Also it does not adhere to the cured rubber, therefore cured rubber punch could be easily taken out from the die. Moreover deformation of mild steel die is negligible. The mild steel die is made of two parts (split type). Its assembly drawing is shown in Figure 8. Two parts of the die are symmetric to each other. To make the die, a rectangular steel block is cut in to two pieces and their surfaces are polished to get smooth surface. Then two parts are tacked welded and machining is done on the welded assembly to obtain the exact internal dimension of die. The inner surface of die is polished to obtain very smooth surface as the shape of rubber punch and preform depends on the surface finish of die. Four steel plates (125X25X10 mm) with a dowel hole (Φ8) and two Ml2 holes on each plate (shown in Figure 8) are welded. To sustain high pressure, supporting webs are provided on the steel plates. Then the halves of the welded assembly are detached by breaking the welded points. As the component prepared is of only 1.5 mm thick, a single die set is used for preparing rubber punch as well as FRP components. However to prepare thicker component two die sets will be required, one for preparing the rubber punch and another one for preparing the component. In that case the internal dimension of the die to prepare rubber punch should be less and upset by thickness of component. The schematic of rubber punch is shown in Figure 9. Five types of rubber (natural, butyl, silicon, styrene butadiene and polybutadiene) are used to cast five different rubber punches. The rubber punch that is to cast have a same inner shape that of FRP component. The die used to cast the rubber punch is same that is used to prepare the component i.e. split steel die. This butyl rubber punch (as representative) is shown in Figure 10. The whole assembly with butyl rubber punch is shown in Figure 11. The fiber reinforced plastic product using this butyl rubber is shown in Figure 12. Burn test, coin test and microstructure study are performed to check the quality of products like volume fraction of fiber, void content, possibility of delamination, interaction between fiber and matrix, etc. The results are compared with those obtained using conventional method. This test has been conducted for cylindrical, conical and flat part of the FRP pump cap. Five specimens are cut from each sections of pump cap, i.e. cylindrical, conical and flat surfaces. Burn test data for the products are given in Table 31. It is clear from these results that the FRP composites produced by RPM technique have good quality and uniform distribution of fibers and matrix. The volume fraction of fiber is in between 45 to 53% using a pressure of 0.5 MPa. Void content in all cases is less than 3.0%. In coin test, a metallic sound is observed which indicates no delamination and good quality of laminate. Scanning electron microscopy studies show that there is uniform distribution of fibers and matrix in the composites prepared by RPM technique. The SEM photographs are shown in Figures 2,3 and 4. Table 31: The fiber volume fraction including % of void in the product made of rubber pressure moulding technique using natural rubber, butyl rubber, silicone rubber, polybutadiene rubber and styrene butadiene rubber (Table Removed) The tension test is conducted on the specimen made of glass fiber and polyester/epoxy resin with 0° fiber orientation prepared by the conventional and rubber pressure molding using butyl rubber, natural rubber, styrene butadiene rubber, polybutadiene rubber and silicone rubber to find out the suitability of new process. The results of mechanical properties using both techniques are given in Tables 13 to 30. The specimens are failed at the center portion and the facture line makes 45° to the line of loading. The stress strain curve is linear at the low loading but non-linear at the higher loading due to the breaking of fiber. Advanced fiber composite materials are very attractive for application in structures where a high specific stiffness and specific strength are important. However, one limitation of their application is the low inter laminar fracture toughness. A major failure mode in laminated composites is a delamination between the laminated layers. These laminates are susceptible to delamination when subjected to an inter laminar stress concentration by impact loadings. Defects like microcracks, voids, inclusions, etc. tend to grow in an inter laminar mode. The existence of delamination which occurs due to the low inter laminar fracture toughness, will lead not only to a loss of stiffness but also to a considerable degradation in the strength and expected material life. Therefore, the inter laminar fracture toughness is an important factor that must be considered in the design and use of fiber composite structures. The average value of inter laminar fracture toughness for the specimen made of polyester resin using conventional method with volume fraction of fiber 40% is 436 J/m2 (Table 13). The average value of inter laminar fracture toughness for the specimen made by rubber pressure moulding technique using butyl rubber is 463 J/m2 (Table 13). Here the volume fraction of fiber is 40% and the matrix is polyester resin. Composite materials are made of several laminates bonded together by the matrix. As such, delamination failure is likely to occur under shear stress conditions. Inter laminar shear strength (ILSS) is an important material property for the design of laminated composite structures subjected to the transverse loads. Hence inter laminar shear test is carried out to determine the inter laminar shear strength of the composites. The inter laminar shear strength is determined by short beam test method. The specimens of size 20 mm x 10 mm x 2 mm are prepared using rubber pressure moulding and conventional methods. The test is conducted on specimens with 0° orientation of warp fibers along loading direction. The average value of inter laminar shear strength for the specimen made of polyester resin using conventional method with volume fraction of fiber 40% is 30 MPa (Table 14). The average value of inter laminar shear strength for the specimen made by rubber pressure moulding technique using butyl rubber is 39 MPa (Table 14). Here the volume fraction of fiber is 40% and the matrix is polyester resin. The average value of tensile strength (Table 15) of the specimen made of polyester resin using conventional method is 342 MPa. But the average value of tensile strength of the specimens prepared by rubber pressure moulding technique using butyl rubber and polyester resin is 288 MPa. Similarly the average values of tensile elastic modulus and % of elongation of the specimens made by the conventional method are 20 GPa and 2% respectively, where as the average values of tensile elastic modulus and % of elongation of the specimens prepared by RPM technique using butyl rubber and polyester resin are 17.5 GPa and 2% respectively. It is clear from the above observation that the tensile strength of specimens made by RPM method is marginally lower than that of the specimens made by conventional method. The elastic modulus of the specimens prepared by RPM technique using natural rubber also gives marginally lower value than that of the specimens prepared by conventional method. The variations of percentages of elongation of the specimens made by both methods are negligible and the average values are with in experimental error bands. The average value of tensile strength (Table 16) of the specimen made of polyester resin using the conventional method is 300 MPa. But the average value of tensile strength of the specimens prepared by RPM technique using natural rubber and polyester resin is 316 MPa (Table 16). Similarly the average values of tensile elastic modulus and % of elongation (Table 16) of the specimens made of polyester resin using conventional method are 14 GPa and 4.2 respectively, where as the average values of tensile elastic modulus and % of elongation of (Table 16) the specimens prepared by RPM technique using natural rubber and polyester resin are 16 GPa and 4.3 respectively. It is clear from the above observation that the tensile strength of specimens made by RPM method is higher than that of the specimens made by conventional method. The elastic modulus of the specimens prepared by rubber pressure moulding technique using natural rubber also gives higher value than that of the specimens prepared by conventional method. The variations of percentages of elongation of the specimens made by both methods are negligible. The average value of inter laminar fracture toughness (Table 17) for the specimen made of polyester resin using conventional method with volume fraction of fiber 49% is 424 J/m2. The average value of inter laminar fracture toughness for the specimen made by rubber pressure moulding technique using natural rubber and polyester resin is 475 J/m2. Here the volume fraction of fiber is 52%. This shows that the specimens prepared by using natural rubber have inter laminar facture toughness higher by 11% compared to specimen prepared by conventional method. The average value of inter laminar shear strength for the specimen made of polyester resin using conventional method with volume fraction of fiber 53% is 18 MPa (Table 18), whereas the average value of inter laminar shear strength for the specimen made by rubber pressure moulding technique using natural rubber is 19.5 MPa (Table 18). Here the volume fraction of fiber is 52% and the matrix is polyester resin. Now the composite materials are made of glass fiber and epoxy resin. The average value of inter laminar fracture toughness (Table 19) for the specimen made by rubber pressure moulding method using natural rubber is 166 J/m2, where as the average value of inter laminar fracture toughness for the specimen made by rubber pressure moulding technique using butyl rubber is 208 J/m2. This shows that the specimens prepared by butyl rubber have inter laminar facture toughness higher than the specimen prepared by natural rubber. Similarly the average value of inter laminar shear strength for the specimen made of epoxy resin using natural rubber is 25 MPa (Table 19), whereas the average value of inter laminar shear strength for the specimen made by butyl rubber is 59 MPa (Table 19). The tensile strength, modulus of elasticity and elongation at break of composite materials prepared by rubber pressure moulding technique using natural rubber and epoxy resin are 309 MPa, 20 GPa and 2% respectively, where as for butyl rubber these are 346 MPa, 21 GPa and 2.2% respectively. This clearly shows the composite materials made of epoxy resin and glass fiber using rubber pressure moulding technique is very good in the case of butyl rubber compared to natural rubber. Again the composite materials are made of glass fiber and polyester resin. The mechanical properties (Table 21) of these composite materials are compared with the conventional method and rubber pressure moulding technique using butyl rubber. The average value of inter laminar fracture toughness (Table 21) for the specimen made by conventional method is 435 J/m , where as the average value of inter laminar fracture toughness for the specimen made by rubber pressure moulding technique using butyl rubber is 470 J/m . This shows that the specimens prepared by butyl rubber have higher inter laminar facture toughness than the specimen prepared by conventional method. Similarly the average value of inter laminar shear strength for the specimen made by conventional method is 30 MPa (Table 21), whereas the average value of inter laminar shear strength for the specimen made by butyl rubber is 40 MPa (Table 21). The tensile strength, modulus of elasticity, elongation at break and Poisson's ratio of composite materials prepared by conventional method are 340 MPa, 20 GPa, 2% and 0.19% respectively, where as for butyl rubber these are 338 MPa, 20 GPa, 2% and 0.19 respectively. Now the composite materials are made of glass fiber and polyester resin using rubber pressure moulding technique. The mechanical behaviors are compared with respect to polybutadiene and butyl rubber. The average value of inter laminar fracture toughness (Table 22) for the specimen made by polybutadiene rubber is 450 J/m2, where as the average value of inter laminar fracture toughness for the specimen made by butyl rubber is 470 J/m2. This shows that the specimens prepared by butyl rubber have higher inter laminar facture toughness than the specimen prepared by polybutadiene rubber. Similarly the average value of inter laminar shear strength for the specimen made by polybutadiene rubber is 37 MPa (Table 22), whereas the average value of inter laminar shear strength for the specimen made by butyl rubber is 40 MPa (Table 22). The tensile strength, modulus of elasticity, elongation at break, and Poisson's ratio of composite materials prepared by rubber pressure moulding technique using polybutadiene rubber are 330 MPa, 18 GPa, 2% and 0.19 respectively, where as for butyl rubber these are 338 MPa, 20 GPa, 2% and 0.19 respectively. This clearly shows the composite materials made of polyester resin and glass fiber using rubber pressure moulding technique is good in the case of butyl rubber compared to polybutadiene rubber. The mechanical behaviors of composite materials prepared by rubber pressure moulding technique using epoxy resin are compared with respect to polybutadiene and butyl rubber. The average value of inter laminar fracture toughness (Table 23) for the specimen made by polybutadiene rubber is 175 J/m2, where as the average value of inter laminar fracture toughness for the specimen made by butyl rubber is 208 J/m2. This shows that the specimens prepared by butyl rubber have higher inter laminar facture toughness than the specimen prepared by polybutadiene rubber. Similarly the average value of inter laminar shear strength for the specimen made by polybutadiene rubber is 44 MPa (Table 23), whereas the average value of inter laminar shear strength for the specimen made by butyl rubber is 59 MPa (Table 23). The tensile strength, modulus of elasticity, elongation at break, and Poisson's ratio of composite materials prepared by rubber pressure moulding technique using polybutadiene rubber are 338 MPa, 19.5 GPa, 2.1% and 0.19 respectively, where as for butyl rubber these are 346 MPa, 21 GPa, 2.2% and 0.19 respectively. This clearly shows the composite materials made of epoxy resin and glass fiber using rubber pressure moulding technique is good in the case of butyl rubber compared to polybutadiene rubber. Now the composite materials are made of glass fiber and polyester resin using conventional method and rubber pressure moulding technique. The mechanical behaviors are compared with respect to these methods. The average value of inter laminar fracture toughness (Table 24) for the specimen made by conventional method is 435 J/m2, where as the average value of inter laminar fracture toughness for the specimen made by polybutadiene rubber is 450 J/m2. This shows that the specimens prepared by polybutadiene rubber have higher inter laminar facture toughness than the specimen prepared by conventional method. Similarly the average value of inter laminar shear strength for the specimen made by conventional method is 30 MPa (Table 24), whereas the average value of inter laminar shear strength for the specimen made by polybutadiene rubber is 37 MPa (Table 24). The tensile strength, modulus of elasticity, elongation at break, and Poisson's ratio of composite materials prepared by conventional method are 340 MPa, 20 GPa, 2% and 0.19 respectively, where as for butyl rubber these are 330 MPa, 18 GPa, 2% and 0.19 respectively. This clearly shows the composite materials made of polyester resin and glass fiber using rubber pressure moulding technique is good with respect to inter laminar fracture toughness and inter laminar shear strength. The mechanical behaviors of composite materials prepared by rubber pressure moulding technique using polyester resin are compared with respect to silicone and butyl rubber. The average value of inter laminar fracture toughness (Table 25) for the specimen made by silicone rubber is 490 J/m , where as the average value of inter laminar fracture toughness for the specimen made by butyl rubber is 470 J/m2. This shows that the specimens prepared by silicone rubber have higher inter laminar facture toughness than the specimen prepared by butyl rubber. Similarly the average value of inter laminar shear strength for the specimen made by silicone rubber is 60 MPa (Table 25), whereas the average value of inter laminar shear strength for the specimen made by butyl rubber is 40 MPa (Table 25). The tensile strength, modulus of elasticity, elongation at break, and Poisson's ratio of composite materials prepared by rubber pressure moulding technique using silicone rubber are 360 MPa, 22 GPa, 2% and 0.19 respectively, where as for butyl rubber these are 338 MPa, 20 GPa, 2% and 0.19 respectively. This clearly shows the composite materials made of polyester resin and glass fiber using rubber pressure moulding technique is good in the case of silicone rubber compared to butyl rubber. Again the mechanical behaviors of composite materials prepared by epoxy resin and glass fiber are compared with respect to silicone and butyl rubber. The average value of inter laminar fracture toughness (Table 26) for the specimen made by silicone rubber is 205 J/m , where as the average value of inter laminar fracture toughness for the specimen made by butyl rubber is 208 J/m . Similarly the average value of inter laminar shear strength for the specimen made by silicone rubber is 55 MPa (Table 26), whereas the average value of inter laminar shear strength for the specimen made by butyl rubber is 59 MPa (Table 26). The tensile strength, modulus of elasticity and elongation at break of composite materials prepared by rubber pressure moulding technique using silicone rubber are 342 MPa, 21 GPa, and 2.1% respectively, where as for butyl rubber these are 346 MPa, 21 GPa and 2.2% respectively. This clearly shows the composite materials made of epoxy resin and glass fiber using rubber pressure moulding technique have equivalent mechanical properties in the case of silicone and butyl rubber. Now the composite materials are made of glass fiber and polyester resin using conventional method and rubber pressure moulding technique using silicone rubber. The mechanical behaviors are compared with respect to these methods. The average value of inter laminar fracture toughness (Table 27) for the specimen made by conventional method is 435 J/m2, where as the average value of inter laminar fracture toughness for the specimen made by silicone rubber is 490 J/m2. This shows that the specimens prepared by silicone rubber have higher inter laminar facture toughness than the specimen prepared by conventional method. Similarly the average value of inter laminar shear strength for the specimen made by conventional method is 30 MPa (Table 27), whereas the average value of inter laminar shear strength for the specimen made by polybutadiene rubber is 60 MPa (Table 27). The tensile strength, modulus of elasticity, elongation at break, and Poisson's ratio of composite materials prepared by conventional method are 340 MPa, 20 GPa, 2% and 0.19 respectively, where as for silicone rubber these are 360 MPa, 22 GPa, 2% and 0.19 respectively. This clearly shows the composite materials made of polyester resin and glass fiber using rubber pressure moulding technique is very good with respect to the conventional method. The tension test is conducted on the composite specimens with 0° fiber orientation prepared by the conventional and rubber pressure molding using natural rubber for various filler-rubber compositions. The composite materials are prepared from polyester resin and glass fiber. The results of tension test are given in Table 28. Figure 13 shows the variation of tensile strength of composite materials prepared by rubber pressure moulding technique using natural rubber having various loading of carbon black. The average value of tensile strength of the specimen made by the conventional method is 300 MPa. The average values of tensile strength of the specimens prepared by RPM technique using natural rubber are 294, 336, 352, 342, 330 and 353 MPa for 0, 15, 30, 45, 60 and 75 phr (per hundred rubber) carbon black loading respectively. It is clear from these data that the variation in the average value of tensile strength due to varying carbon black content is within a range of 59 MPa. Similarly the average value of tensile elastic modulus of the specimens made by the conventional method is 14.2 GPa, where as the average values of tensile elastic modulus of the specimens prepared by RPM technique using natural rubber are 15.3,16.5,16.0,14.8,16.1 and 18.1 GPa for 0,15, 30, 45, 60 and 75 phr (per hundred rubber) carbon black loading respectively. The average value of inter laminar fracture toughness for the specimen made by conventional method with volume fraction of fiber 49% is 424 J/m2. The average values of inter laminar fracture toughness for the specimen made by RPM technique using natural rubber are 410, 398, 476, 446, 472 and 386 J/m2 for the carbon black loading of 0, 15, 30, 45, 60 and 75 phr respectively (Table 29). A graph showing the variation of inter laminar fracture toughness of composite laminate made by RPM Technique with increase in the carbon black loading in the natural rubber is shown in Figure 14. Similarly the average value of inter laminar shear strength for the specimen made by conventional method is 18.5 MPa (Table 30), whereas the average values of inter laminar shear strength for the specimens made by natural rubber containing carbon black loading of 0, 15, 30, 45, 60 and 75 phr are 11, 11, 17,13, 20, and 13 MPa (Table 30). A graph showing the variation of inter laminar fracture shear strength of composite laminates made by RPM Technique with increase in the carbon black loading in the natural rubber is shown in Figure 15. Main advantages of the Invention: a. It is possible to fabricate a curved surface using this novel technique b. Developed pressure applied is hydrostatic even on vertical walls, which enables to maintain product uniformity within the single part. c. Rubber punch can be made from the same mold using an appropriate spacing material (for thin wall products of wall thickness less than 1.5 mm, spacing material is not required as rubber is flexible enough to deform. d. Same rubber punch can be used several times. e. The new method entitled rubber pressure moulding avoids the use of costly porous release material, which is required in the conventional process using autoclave moulding. f. The new method entitled rubber pressure moulding avoids the use of costly bleeder material, which is required in the conventional process using autoclave moulding. g. The new method entitled rubber pressure moulding avoids the use of costly nonporous release material, which is required in the conventional process using autoclave moulding. h. The new method entitled rubber pressure moulding avoids the use of costly breather material, which is required in the conventional process using autoclave moulding. i. The new technique does not require any autoclave, which is very costly equipment in the conventional process. j. The product manufactured from this new technique has better mechanical properties than those of the conventional method. k. Tooling cost is low 1. At last, the processing cost is very low compared to the conventional process. m. The new technique has a great potential in the manufacturing of fiber reinforced components for aerospace and automobile industries. We claim: 1. A process of manufacturing a fiber reinforced plastic (FRP) article using flexible material pressure moulding technique, said process comprising: a) obtaining a perform comprising sandwiched glass fabric having appropriate shape carved out from a fiber sheet and a matrix of a thermosetting polymer; b) placing the perform on a flexible punch coated with one or more coating agent selected from the group consisting of polytetrafluoro ethylene, polyvinyl alcohol, silicone emulsion and detergent/ soap solution; c) placing the flexible punch with the perform in a split die, wherein the split die consisting of two or more portions; d) bolting the split die using bolts till the two portion of the split die touches each other to obtain a bolted split die; e) loading the bolted split die to a lower platen of a hydraulic press and applying the hydraulic pressure for closing the bolted split die and allowing the perform to cure at room temperature for about 16 hours; f) obtaining a cured product by loosing the bolt to open the split die and taking out the flexible punch; and g) repeating the above steps for continuously producing the FRP product. 2. A process as claimed in claim 1, wherein the fiber sheet is selected from the group consisting of woven glass fabrics, glass mat-non woven and continuous fiber. 3. A process as claimed in claim 1, wherein the matrix of thermosetting polymer is selected from an epoxy resin composition containing a hardener in a weight ratio in the range of 100:1 to 100:20; or a polyester resin composition comprising a catalyst and a hardener in a weight ratio in the range of 100:1:1 to 100: 3:3. 4. A process as claimed in claim 1, wherein the thermosetting polymer is selected from a polyester resin, or an epoxy resin; and/or combination thereof. 5. A process as claimed in claim 3, wherein the hardener is methyl ethyl ketone. 6. A process as claimed in claim 1, wherein the split die consists of a top portion, a bottom portion containing more than two pieces and optionally a cone type inner core. 7. A process as claimed in claim 1 wherein, the split die is made of a material selected from the group consisting of mild steel, carbon steel, carbon manganese steel, alloy steel and nickel-chromium hard chrome plating stainless steel. 8. A process as claimed in claim 1 wherein the hydraulic pressure is about 0.4 MPa to 1.0 MPa and the perform is allowed to cure at room temperature for about 10 to 20 hours, preferably 16 hours. 9. A process as claimed in claim 1 wherein the flexible punch is a rubber punch made up of a rubber compound. 10. A process as claimed in claim 9, wherein the rubber compound comprising a base rubber or combination of one or more rubber and other rubber compounding ingredients, such as reinforcing filler selected from carbon black, silica or combination thereof, metal oxide, fatty acid, process oil(s), vulcanizing agent(s), or accelerator(s) and optionally one or more antioxidant. 11. A process as claimed in claim 10, wherein the base rubber is selected from the group consisting of natural rubber, synthetic polyisoprene rubber, styrene-butadine rubber, polybutadine rubber, isoprene-isobutlylene rubber (IIR or butyl rubber), silicone rubber, fluorocarbon rubber, and polychloroprene rubber or combination thereof. 12. A process as claimed in claim 10, wherein the metal oxide is selected from zinc oxide, calcium oxide, magnesium oxide, or lead oxide, which is in the range of 2 to 6 parts per hundred rubber (phr). 13. A process as claimed in claim 10, wherein the fatty acid is selected from the group consisting of stearic acid, palmitic acid, and oleic acid, which is in the range of 2 to 6 parts per hundred rubber (phr). 14. A process as claimed in claim 10, wherein the reinforcing filler is selected from one or more carbon black selected from the group consisting of ISAF, HAF, FEF, GPF, SPvF and other grades of commercially available carbon blacks, which is in the range of 25 to 70 parts per hundred rubber (phr) and /or silica filler. 15. A process as claimed in claim 10, wherein the process oil is a low staining or non-staining process oil, selected from paraffinic oil, naphthenic oil, vegetable oil or combination thereof, which is in the range of 2 to 10 parts per hundred rubber (phr). 16. A process as claimed in claim 10, wherein the antioxidant is selected from a the group consisting of condensation product of acetone and diphenyl amine, phenyl-betanapthylamine, blend of diphenyl-p-phenylene diamine and arylamine, blend of arylamines, polymerized 1,2 dihydro 2,2,4- trimethyl quinoline, N-(l,3 -dimethylbutyl)-N'-phenyl-p-phenylene-diamine, diaryl para phenylene diamines, and 2-mercapto benz imidazole or combination thereof, which is in the range of 0 to 4 parts per hundred rubber (phr). 17. A process as claimed in claim 10, wherein the vulcanizing agent is selected from the group consisting of sulphur, dicumyl peroxide, phenol-formaldehyde resin, and Zinc oxide or combination thereof which is in the range of 0.5 to 12 parts per hundred rubber (phr). 18. A process as claimed in claim 10, wherein the accelerator used is selected from the group consisting of tert-butylbenzthiazyl sulphenamide, 2-(4-morpholinyl mercapto)-benzthiazole, blend of thiazole and thiuram, dicyclohexyl benzthiazyl sulphenamide, blend of dithiocarbamates, thiazole, cyclohexyl benzthiazyl sulphenamide, 2-mercaptobenzthiazole, dibenzthiazyl disulphide, tetramethylthiuram disulfide, zinc diethyl dithiocarbamate, zinc salt of mercaptobenzthiazole, 4-4' dithiodimorpholine, and dicumyl peroxide, which is in the range of 0.5 to 6 parts per hundred rubber (phr). 19. A process as claimed in claim 10, wherein the rubber compound is prepared by mixing the rubber and other compounding ingredients by methods selected from open mill mixing using two-roll mill and internal mixing using kneader, intermix and banbury mixer. 20. A process as claimed in claim 10, wherein the rubber punch is prepared by methods selected from the group consisting of compression moulding, transfer moulding and injection moulding by curing required quantity of the compounded rubber in a mould at a temperature in the range of 140 to 170°C using a hydraulic pressure of about 1 to 10 MPa for a period ranging between 10 to 100 minutes. 21. A process of manufacturing fiber reinforced plastic (FRP) articles using flexible material pressure moulding technique as herein described with reference to examples and drawings.

Documents:

2078-DEL-2004-Abstract-(12-10-2011).pdf

2078-del-2004-abstract.pdf

2078-DEL-2004-Claims-(12-10-2011).pdf

2078-del-2004-claims.pdf

2078-DEL-2004-Correspondence Others-(12-10-2011).pdf

2078-del-2004-correspondence-others.pdf

2078-del-2004-description (complete).pdf

2078-del-2004-drawings.pdf

2078-del-2004-form-1.pdf

2078-del-2004-form-18.pdf

2078-del-2004-form-2.pdf

2078-del-2004-form-26.pdf

2078-del-2004-form-3.pdf

2078-del-2004-form-5.pdf

2078-DEL-2004-GPA-(12-10-2011).pdf