Title of Invention	AN IMPROVED PROCESS FOR THE MANUFACTURE OF GLASS-POLYMER HYBRID MULTI - LAYER LAMINATES HAVING ENHANCED FAILURE RESISTANCE AND GLASS-POLYMER HYBRID MULTI - LAYER LAMINATES MADE THEREBY
Abstract	An improved process for the manufacture of glass - polymer hybrid multi-layer laminates having enhanced failure resistance which comprises cleaning glass substrates by known methods, drying the cleaned glass substrates followed by coating the said cleaned and dried glass substrates with an oily film, over the said oily film coating applying a polymeric layer of thickness in the range of 22-360 µm to obtain oily film and polymer coated glass substrates, optionally providing layer of reinforcing material over the said coated glass substrates, making a stack of plurality of said coated glass substrates, laminating the said stack so obtained under uniaxial pressure in the range of 2-10 KPa at room temperature for a period in the range of 10-15 hrs.

Title of Invention

AN IMPROVED PROCESS FOR THE MANUFACTURE OF GLASS-POLYMER HYBRID MULTI - LAYER LAMINATES HAVING ENHANCED FAILURE RESISTANCE AND GLASS-POLYMER HYBRID MULTI - LAYER LAMINATES MADE THEREBY

Abstract

An improved process for the manufacture of glass - polymer hybrid multi-layer laminates having enhanced failure resistance which comprises cleaning glass substrates by known methods, drying the cleaned glass substrates followed by coating the said cleaned and dried glass substrates with an oily film, over the said oily film coating applying a polymeric layer of thickness in the range of 22-360 µm to obtain oily film and polymer coated glass substrates, optionally providing layer of reinforcing material over the said coated glass substrates, making a stack of plurality of said coated glass substrates, laminating the said stack so obtained under uniaxial pressure in the range of 2-10 KPa at room temperature for a period in the range of 10-15 hrs.

Full Text	The present invention relates to an improved process for the manufacture of glass -polymer hybrid multi-layer laminates having enhanced failure resistance and glass -oolymer hybrid multi-layer laminates made thereby. The main usage of this hybrid multi-layer laminate structure is as aamage tolerant natenal that can sustain stress even after onset of fracture. Yet another application is as structural material for load bearing engineering applications. The other important application is as opaque window pane. Another major application is as artificial separators used with wooden or aluminium frames as space dividers for interior decoration. Reference may be made to US Patent no. 5,972,819 (1999) wherein a damage tolerant material was disclosed t,: be a multi-layer structure comprising of a top layer of 85-90% dense cylindrical alumina pellets arranged in a plurality of adjacent rows backed up by a laminate comprising of layers of a plurality of adjacent layers comprising of a plurality of unidirectional fibers embedded in a polymeric matrix where the fibers of adjacent layers must lie at an angle of between 45 degree to 90 degree. It was mentioned that the convexly faced surface of the cylindrical pellets must be directed towards the outer surface of the top facing plate, thus making the process complicated in terms of ease of fabrication. Also there is a severe size restriction that the ratio of diameter (D) to the radius of curvature ( R ) of the curved surface of cylindrical pellets must lie in the range D/R = 0.64:1 to 0.85 : 1, thus making the process less flexible in terms of the choice of material. Further, the use of synthetic fibers make the process less cost effective. Reference may also be made to US Patent no. 6,112,635 (2000) wherein a damage tolerant multi-layer structure has been disclosed to be comprised of plurality of adjacent rows of alumina pellets embedded in aluminium or a thermoplastic resin or a thermosetting resin backed up by tough woven textile material followed by a back up layer of aluminium. There is a severe size restriction that the alumina pellets must be at least 12 mm in length and must be in contact with at least 4 adjacent pellets, thus making 'he process complicated in terms of ease of fabrication. The use of tough woven textile fabrics eg. Aramid fibers or polyamide netting has made the process less cost effective. Further back up layer of aluminium addition makes the process step-wise more lengthier. Reference may also be made to US patent no. 6, 332, 390 (2001) wherein a 0.75 inch to 0.815 inch thick multi-layer damage tolerant structure is disclosed to be comprised of a 0.25 inch thick aramid fiber reinforced polymer matrix laminate facing material backed up by 0.32 inch thick alumina or silicon carbide or boron carbide ceramic tile based second layer followed by 0.06 inch to 0.125 inch thick third layer of glass or ceramic overlay strips used for protection of tile joint and free edge areas, backed up by 0.03 inch thick aramid spall shield. The fabrication process is quite complicated, involves stringent control of individual layer thickness and the use of aramid fibers and aramid nettings make the process less cost effective. Reference may also be made to or co-pending Indian patent application no. 51/DEL/2002 (232797) dt 21-12-2002 wherein we have described and claimed a simple yet cost-effective process for the manufacture of glass-polymer hybrid multi-layer laminates having improved failure resistance and glass-polymer hybrid multi-layer laminates made thereby. The clue to obtaining improvement in failure resistance was found to be linked to the achievement of controlled interfacial de-bonding leading to the growth of delamination cracks through the multi-layer composite architecture that involved alternate placement of a plurality of brittle and strong layers with a weak interface between the two. However, the maximum improvement of failure resistance was limited to only a value of about 270 J/m2. Reference may also be made to an article published in the Journal of the American Ceramic Society, vol. 77, no.8, pp.2081-2087, 1994, wherein glass sheets or slides were used as the matrix material in between alternate interfacial layers of a reinforcing polymer (ie. polyvinyl butyral, a thermoplastic resin) to fabricate the glass-polymer multilayer structure with a maximum of only 5 interfacial layers. The stack of the plurality of alternate glass and polymer layers sealed under vacuum in a specially made envelop, was vacuum hot pressed for three minutes at a high temperature of 175°C under a high uniaxial pressure of 350 KPa, thus making the process stepwise complicated as well as costlier. In addition, the very not pressing technique used for the fabrication technique gave rise to more of strong bonding between the layers, thus causing the material to behave in a more orittle like fashion. Further, no assessment of the failure resistance of the glass-polymer multi-layer composites fabricated by vacuum hot pressing was done. Thus, the major drawbacks of the hitherto known processes are that they are complicated, costlier and the "abrication technique gives rise to strong interfacial bonding. The main object of the present invention is to provide an improved process for the manufacture of glass - polymer hybrid multi-layer laminates having enhanced failure resistance. Another object of the present invention is to provide an improved process for the manufacture of glass-polymer hybrid multi-layer laminates, which is cost effective. Yet another object of the present invention is to provide an improved process to tailor the manufacture procedure of the glass-polymer hybrid multi-layer laminates in terms of the choice of polymeric layer, choice of the number of interfacial layers, laminating pressure so that failure resistance to suit a given end application can be attained. Still another object is to provide a glass-polymer hybrid multi-layer laminates having improved failure resistance. In the present invention, an improved process has been provided to obtain glass polymer hybrid multi-layer laminates with enhanced failure resistance. The enhancement in failure resistance was made possible through controlled interfacial debonding leading to the growth of delamination cracks. The architecture of the multi-layer composite involved alternate placement of a plurality of brittle glass and viscoelastic polymeric layers with a deliberately designed weak interface between the two. In particular the desired variation in the degree of weakness was achieved by the innovative introduction of a thin oily film at the interface between the glass la nd the polymeric layer. In addition, the advantage of the low pressure lamination tecnnique was exploited to further develop the weakness of the interface. This makes the process not only simpler but also cost effective. It has been shown further that depending on the type of oily film, type of reinforcement and the number of reinforcing layers, the failure resistance of the glass polymer hybrid multi-layer composites can be enhanced to a value of as high as about 1341 J/m2 in comparison to a low value of about 5 J/m2 obtained for the brittle glass matrix. Similarly, on the lower side values as small as about 10 J/m2 could also be obtained for the failure resistance of the glass polymer hybrid multi-layer composites, depending on the type of oily film, the type of reinforcement and the number of reinforcing layers. In other words, thus, the present process provides a means to tailor the failure resistance of the glass polymer hybrid multi-layer composites to suit a particular end application. Accordingly, the present invention provides an improved process for the manufacture of glass - polymer hybrid multi-layer laminates having enhanced failure resistance which comprises cleaning glass substrates by known methods, drying the cleaned glass substrates followed by coating the said cleaned and dried glass substrates with an oily film, over the said oily film coating applying a polymeric layer of thickness in the range of 22-360 µm to obtain oily film and polymer coated glass substrates, optionally providing layer of reinforcing material over the said coated glass substrates, making a stack of plurality of said coated glass substrates, laminating the said stack so obtained under uniaxial pressure in the range of 2-10 KPa at room temperature for a period in the range of 10-15 hrs. In an embodiment of the present invention the glass used is such as unannealed / annealed soda lime silica glass, borosilicate glass, aluminosilicate glass. In another embodiment of the present invention the thickness of the glass sheets and slides of thickness is in the range of 0.3 -1.17 mm. In still another embodiment of the present invention the cleaning of the glass substrates is done by washing with detergent solution followed by water for a period in the range of 10 to 2. hinutes. n vet another embodiment of the present invention the rinsing or the glass substrates is lone by rinsing with acetone for a period in the range of 5 to 15 minutes. i still yet another embodiment of the present invention the arying or the cleaned and nnsed glass substrates is done for a period in the range of 10 to20 hours at a temperature n the range of 80 to 120°C. in a further embodiment of the present invention interfacial layers of oily film is such as Kerosene, gasolene, n-Heptadecane, n-Nonadecane. !n a still further embodiment of the present invention the polymer is a thermosetting resin such as epoxy resins, phenolic resins, melamine formaldehyde resin, siiicone resins. in another embodiment of the present invention the polymer is a thermoplastic resin such as polyvinyi butyral, polyvinyl ester, polyamide. In yet another embodiment of the present invention the reinforcing material is such as woven E -glass fabric, roving. In still another embodiment of the present invention a polymeric layer is provided over the optional layer of reinforcing material. Accordingly, the present invention provides glass - polymer hybrid multi-layer laminates having enhanced failure resistance made by the process of the present invention as described herein. The non-obvious inventive step to achieve the novelty of improved failure resistance of the glass polymer hybrid multi-layer laminates lies in the achievement of controlled debonding through the use of a thin oily film at the interface. The present glass polymer •brid multi-layer laminates are provided with an alternate brittle-strong architecture naving a deliberately introduced weak interfacial bonding between the brittle layer and the strong layer. The weak interfaciai bonding is a consequence of (a) the oily film provided curing fabrication and (b) the low pressure lamination techniaue applied at room emperature. Particularly the presence of the oily film makes ;he strong interfacial ;onesion aifficuil to oe acrneved. Because the interfacial bonding ,s deliberately kept weak, as the onttle glass layer fails, the interfacial polymeric layer takes up the load and then, a local delamination crack ensues at the interface when the reinforcing layer takes up the load. On continued loading, this reinforcing layer breaks up eventually when the next brittle layer takes up the load again. The continuation of this process gives rise to a process of controlled debonding manifested as a stepped load deflection behaviour of the glass polymer hybrid multi-layer laminates, which, in the process, consume much higher amount of strain energy from the loading system thus, enhancing their own failure energy values manifold over that of the corresponding glass matrix layers. In contrast to this pseudo-ductile nature of load deformation behavior in the glass polymer hybrid multi-layer laminates, the brittle glass matrix shows a characteristic fast fracture behavior and hence a much lower value of failure energy. In the prior art damage tolerant multi-layer structures were developed by using either dense ceramic bodies of particular geometry and size embedded in metallic or polymeric matrix with or without a backing up layer of tough woven textile fabrics based laminate occasionally having support of a further backing up layer of light metallic materials thus, making the processes complicated in terms of ease of fabrication and less cost effective because of the utilization of cost intensive synthetic fibers. Also, in the prior art attempts were made to develop glass -polymer multi-layer structures with a stack of plurality of alternate glass and polymer layers vacuum sealed and vacuum hot pressed for three minutes at a high temperature of 175°C under a high uniaxial pressure of 350 KPa, which reduced second phase to a volume fraction of only 0.01. This is so because most of the resin had flown out at high temperature and pressure of hot pressing. Thus the earlier work had the drawbacks of involving complicated steps, cost ineffectiveness and possibility of strong interfacial bonding. In the present invention these drawbacks are obviated through the provision of a simpler and much less costlier process for the fabrication of glass-polymer hybrid multilayer laminates having the novelty of improved resistance to failure. This was achieved by the non-obvious inventive step of providing an oily interfacial film during the process of low pressure lamination of a plurality of alternate glass and a polymeric layer at room 'emperature. This inventive step of presence of a oily film deterring interfacial cohesion along with the technique of lamination at low pressure and room temperature caused a A/eak interfaciai bonding between the plurality of glass and polymer layers. This weak intertacial bonding promoted more of controlled debonding when the glass-polymer hybrid multi-layer laminate was subjected to stress. This controlled debonding led to a stepped :oad deformation behaviour, thus providing improved resistance to failure. The details of the process steps of the present invention are: 1. Annealed/unannealed glass sheets and slides of thickness in the range of 0.3-1.17 mm are washed with detergent solution followed by water for 10-20 mins. 2. Washed glass sheets and slides are rinsed with acetone for 5-15 minutes. 3. Rinsed glass sheets and slides are dried for 10-20 hrs at 80-120°C in air. 4. Dried glass sheets and slides are kept in a desiccator for 12-36 hrs. at room temperature. 5. Oily Film is applied by conventional means on one side of glass sheets and slides. 6. Polymeric layer of thickness « 22-360 jam thickness is applied by conventional methods on one side of the glass sheets and a stack of plurality of alternate glass, oily film and polymer layer is made. Optionally, an additional layer of woven e- glass fabric or roving may be provided along with a polymeric coating. 7. The stack of material obtained in step 5 is laminated in a laboratory press under a uniaxial pressure of 2-10 KPa at room temperature (25-33°C) for a period of 10-15 hrs. to obtain the glass-polymer hybrid multilayer laminates.The following examples are given by way of illustration ana therefore should not be construed to limit the scope of the present invention. EXAMPLE-1 ro fabricate glass polymer hybrid multi-layer laminates, eleven numbers of thin square glass sheets was obtained commercially. The glass was a soda lime silica glass. The ength. breadth and thickness was measured by callipers. The average dimension was 18 mm and thickness 0.3 mm. The square glass sheets were washed with detergent solution •nci flowing, doubly distilled water for a period of 20 minutes. The glass sheets were mally rinsed with acetone for 15 minutes prior to putting in an air oven. The time of drying was 18 hrs. at 100°C. Finally, the glass sheets were placed in a desiccator for 12 hrs prior to application of the epoxy polymeric layer and a E-glass woven fabric by a hand lay-up technique. Thus, a plurality of stack of alternate glass sheet and polymeric layer was neveloped with ten interfacial epoxy layer kept between the glass disks. The lamination of this stack of plurality of alternate glass plate layer and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 2 KPa applied at room temperature (25°C) for a period of 10 hrs. The average density of the laminate was 1.80 gm/cc. The polymer layer had a thickness of 258 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multilayer laminates in a universal testing machine and compared to that of the matrix glass disk. For the laminate, the failure energy was 164 J/m2 as compared to the low failure energy of 5.03 J/m2 obtained for the thin matrix glass sheets. EXAMPLE-2 To fabricate glass polymer hybrid multi-layer laminates, two number of thin circular glass disks was obtained commercially. The diameter and thickness were measured by a callipers. The average diameter was 18 mm and thickness 0.3 mm. The alass discs were vashfcu with detergent and flowing, aouoly distilled water for a period or 15 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 10 minutes prior to putting in an air oven. The time of drying was 15 hrs. at 120°C. Finally, the glass disks were placed in a desiccator for 24 hrs prior to application of a thin layer of kerosene using a spray gun. Next, the epoxy polymeric layer was placed by using a paint brush along with the placement of a woven E-glass fabric cloth for reinforcement. Thus, a stack of alternate glass disk, oily film, polymeric layer reinforced with woven fabric was developed with only 1 interfacial epoxy layer kept between the glass disks. The lamination of this stack of alternate glass disk layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 4 KPa applied at room temperature (30°C) for a period of 15 hrs. The average density value of the laminate was 2.04 gm/cc. The polymer layer had a thickness of 360 micron. Finally, the failure resistance was measured for these glass-pclymer hybrid multi-layer laminate in a universal testing machine and compared to that of the matrix glass disk. For the laminate, the failure energy was 159.84 J/m2 as compared to the low failure energy of 5.03 J/m2 obtained for the thin matrix glass disks. EXAMPLE-3 To fabricate glass polymer hybrid multi-layer laminates, two number of thin circular glass disks was obtained commercially. The diameter and thickness were measured by a callipers. The average diameter was 18 mm and thickness 0.3 mm. The glass discs were washed with detergent and flowing, doubly distilled water for a period of 20 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 5 minutes prior to putting in an air oven. The time of drying was 15 hrs. at 110°C. Finally, the glass disks were placed in a desiccator for 12 hrs prior to application of the epoxy polymeric layer by using a paint brush along with the placement of a E-glass fabric for reinforcement. Thus, a stack of alternate glass disk and polymeric layer was developed with only 1 interfacial epoxy layer reinforced with woven glass cloth kept between the glass disks. The lamination of this stack of alternate glass disk layer and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 6 KPa applied at room temperature (30°C) for a period of 10 hrs. The average density value of :he laminate was 2.03 gm/cc. The polymer layer had a thickness or 358.9 micron. Finally, :he failure resistance was measured for these glass-polymer hybrid multi-layer laminate in a universal testing machine and compared to that of the matrix giass disk. For the aminate, the failure energy was 39.45 J/rrr as compared to the low railure energy of 5.03 J/rrr obtained for the thin matrix glass disks. EXAMPLE - 4 To fabricate glass polymer hybrid multi-layer laminates, eleven number of thin circular giass disks was obtained commercially. The diameter and thickness were measured by a callipers. The average diameter was 18 mm and thickness 0.3 mm. The glass discs were washed with detergent and flowing, doubly distilled water for a period of 20 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 10 minutes prior to putting in an air oven. The time of drying was 36 hrs. at 120°C. Finally, the glass disks were placed in a desiccator for 24 hrs prior to application of a thin film of kerosene by using a paint brush. Next, the epoxy polymeric layer was applied by a hand lay-up technique along with the placement of a E-glass fabric for reinforcement. Thus, a stack of alternate glass disk, oily film and polymeric layer reinforced with woven glass cloth was developed with ten interfacial epoxy layers kept between the glass disks. The lamination of this stack of alternate glass disk layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 10 KPa applied at room temperature (30°C) for a period of 15 hrs. The average density value of the laminate was 2.01 gm/cc. The polymer layer had a thickness of 260 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multilayer laminate in a universal testing machine and compared to that of the matrix glass disk. For the laminate, the failure energy was 1340.66 J/m2 as compared to the low failure energy of 5.03 J/m2 obtained for the thin matrix glass disks. EXAMPLE -5 To fabricate glass polymer hybrid multi-layer laminates, eleven number of thin circular glass disks was obtained commercially. The diameter and thickness were measured by a callipers. The average diameter was 18 mm and thickness 0.3 mm. The glass discs were washed with detergent and flowing, doubly distilled water for a period of 5 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 10 minutes prior to putting in an air oven. The time of drying was 12 hrs. at 120°C. Finally, the glass disks were placed in a desiccator for 24 hrs prior to application of the epoxy polymeric layer by using a paint brush along with the placement of a E-glass fabric for reinforcement. Thus, a stack of alternate glass disk and polymeric layer reinforced with woven glass cloth was developed with ten interfacial epoxy layers kept between the glass disks. The lamination of this stack of alternate glass disk layer and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 8 KPa applied at room temperature (30°C) for a period of 12 hrs. The average density value of the laminate was 2.01 gm/cc. The polymer layer had a thickness of 261.8 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multilayer laminate in a universal testing machine and compared to that of the matrix glass disk. For the laminate, the failure energy was 347.05 J/m2 as compared to the low failure energy of 5.03 J/m2 obtained for the thin matrix glass disks. EXAMPLE - 6 To fabricate glass polymer hybrid multi-layer laminates, two number of thin circular glass disks was obtained commercially. The diameter and thickness were measured by a callipers. The average diameter was 18 mm and thickness 0.3 mm. The glass discs were washed with detergent and flowing, doubly distilled water for a period of 20 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 15 minutes prior to putting in an air oven. The time of drying was 24 hrs. at 110°C. Finally, the glass disks were placed in a desiccat 24 hrs prior to application of a thin layer of Heptadecane by using a hand spray gu, jext, the epoxy polymeric layer was applied using a paint brush along with the placement of a t-glass fabric for reinforcement. ""hus. a stack of alternate glass disk, oily film and polymeric layer reinforced with woven :jiass cloth was developed with only 1 interfacial epoxy layer kept between the glass 3isks. The lamination of this stack of alternate giass disk layer, oily film and polymeric iayer was done in a conventional laboratory press under a low uniaxial pressure of 4 KPa applied at room temperature (30°C) for a period of 10 hrs. The average density value of ihe laminate was 2.03 gm/cc. The polymer layer had a thickness of 354 micron. Finally, rhe failure resistance was measured for these glass-polymer hybrid multi-layer laminate in a universal testing machine and compared to that of the matrix glass disk. For the iaminate, the failure energy was 153.69 J/m2 as compared to the low failure energy of :.03 J/m2 obtained for the thin matrix glass disks. EXAMPLE - 7 To fabricate glass polymer hybrid multi-layer laminates, two number of thin circular glass disks was optamed commercially. The diameter was measured by a callipers. Using the same instrument, the thickness of the disks was measured. The average diameter was 18 mm and thickness 0.3 mm. The glass discs were washed with detergent and flowing, doubly distilled water for a period of 10 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 10 minutes prior to putting in an air oven. The time of drying was 12 hrs. at 80°C. Finally, the glass disks were placed in a desiccator for 24 hrs prior to application of a thin film of n-Octadecane by a hand spray gun. Next, the epoxy polymeric layer was applied by using a paint brush along with the placement of a E-giass fabric for reinforcement. Thus, a stack of alternate glass disk, oily film and polymeric layer reinforced with woven glass cloth was developed with only 1 interfacial epoxy layer kept between the glass disks. The lamination of this stack of alternate glass disk layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 2 KPa applied at room temperature (30°C) for a period of 10 hrs. The average density value of the laminate was 2.04 grn/cc. The polymer layer had a thickness of 359.2 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multi-layer laminate in a universal testing machine ana compared to that of the matrix glass disk. For the laminate, the failure energy was 145.22 J/m2 as compared to the low failure energy of 5.03 J/m" obtained for the thin -natnx glass disks. EXAMPLE - 3 To fabricate glass polymer hybrid multi-layer laminates, two number of thin circular glass disks was obtained commercially. The diameter and thickness were measured by a callipers. The average diameter was 18 mm and thickness 0.3 mm. The glass discs were washed with detergent and flowing, doubly distilled water for a period of 5 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 15 minutes prior to putting in an air oven. The time of drying was 18 hrs. at 120°C. Finally, the glass disks were placed in a desiccator for 24 hrs prior to application of a thin film of n-Nonadecane using a hand spray gun. Next, the epoxy polymeric layer was applied by using a paint brush along with the placement of a E-glass fabric for reinforcement. Thus, a stack of alternate glass disk, oily film and polymeric layer reinforced with woven glass cloth was developed with only 1 interfacial epoxy layer kept between the glass disks. The lamination of this stack of alternate glass disk layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 4 KPa applied at room temperature (30°C) for a period of 10 hrs. The average density value of the laminate was 2.02 gm/cc. The polymer layer had a thickness of 362.3 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multi-layer laminate in a universal testing machine and compared to that of the matrix glass disk. For the laminate, the failure energy was 161.71 J/m2 as compared to the low failure energy of 5.03 J/m2 obtained for the thin matrix glass disks. EXAMPLE - 9 To fabricate glass polymer hybrid multi-layer laminates, two number of thin circular glass disks was obtained commercially. The diameter and thickness were measured by callipers. The average diameter was 18 mm and thickness 0.3 mm. The circular glass jiscs were washed with detergent and flowing, doubly distilled water for a period of 10 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 5 minutes prior to putting in an air oven. The time of drying was 15 hrs. at 100°C. Finally, the glass disks were placed in a desiccator for 24 hrs prior to application of a thin layer of n-lcosane by a hand spray gun. Next, the epoxy polymeric layer was applied by using a paint brush along with the placement of a E-glass fabric for reinforcement. Thus, a stack of alternate glass disk, oily film and polymeric layer was developed with only 1 interfacial epoxy layer kept between the glass disks. The lamination of this stack of alternate glass disk layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 3 KPa applied at room temperature (30°C) for a period of 10 hrs. The average density value of the laminate was 2.03 gm/cc. The polymer layer had a thickness of 358.4 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multi-layer laminate in a universal testing machine and compared to that of the matrix glass disk. For the laminate, the failure energy was 158.62 J/m2 as compared to the low failure energy of 5.03 J/m2 obtained for the thin matrix glass disks. EXAMPLE-10 To fabricate glass polymer hybrid multi-layer laminates, two number of thin circular glass disks was obtained commercially. The diameter and thickness were measured by a callipers. The average diameter was 18 mm and thickness 0.3 mm. The glass discs were washed with detergent and flowing, doubly distilled water for a period of 15 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 10 minutes prior to putting in an air oven. The time of drying was 12 hrs. at 90°C. Finally, the glass disks were placed in a desiccator for 24 hrs prior to application of a thin layer of n-Henicosane using a hand spray gun. Next, the silicone resin polymeric layer was applied by using a paint brush along with the placement of a E-glass roving for reinforcement. Thus, a stack of alternate glass disk, oily film and polymeric layer reinforced with woven glass cloth was developed with only 1 interfacial epoxy layer kept between the glass disks. The lamination of this stack of alternate glass disk layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 6 KPa applied at room temperature (30°C) for a period of 12 hrs. The average density value of :he laminate was 2.03 gm/cc. The polymer layer had a thickness of 359.6 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multi-layer laminate in 3 universal testing machine and compared to that o* the matrix glass disk. For the laminate, the failure energy was 168.35 J/m2 as compared to the low failure energy of 5.03 J/m^ obtained for the thin matrix glass disks. EXAMPLE-11 To fabricate glass polymer hybrid multi-layer laminates, two number of thin circular glass disks was obtained commercially. The diameter and thickness were measured by a callipers. The average diameter was 18 mm and thickness 0.3 mm. The glass discs were washed with detergent and flowing, doubly distilled water for a period of 5 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 10 minutes prior to putting in an air oven. The time of drying was 36 hrs. at 120°C. Finally, the glass disks were placed in a desiccator for 24 hrs prior to application of a thin layer of Gasolene by a hand spray gun. Next, the phenolic resin polymeric layer was applied by using a hand lay-up technique along with the placement of a E-glass fabric for reinforcement. Thus, a stack of alternate glass disk, oily film and polymeric layer was developed with only 1 interfacial epoxy layer kept between the glass disks. The lamination of this stack of alternate glass disk layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 2 KPa applied at room temperature (30°C) for a period of 12 hrs. The average density value of the laminate was 2.2 gm/cc. The polymer layer had a thickness of 358.7 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multi-layer laminate in a universal testing machine and compared to that of the matrix glass disk. For the laminate, the failure energy was 153.58 J/m2 as compared to the low failure energy of 5.2 J/m2 obtained for the thin matrix glass disks. EXAMPLE- 12 "o fabricate glass polymer hybrid multi-layer laminates, three number of thin glass slides vas obtained commercially. The glass used was an aluminosilicate glass. The dimensions were measured by a callipers. The average length was 75 mm, width 18 mm and thickness 1.01 mm. The annealing schedule followed for the glass slides was as rollows : heating from room temperature to 520°C @ 100°C/hr followed by a soak of 1 hour at 520°C and cooling down from 520°C temperature @ 5°C/hr to 300°C and then *inally cooling from 300°C, @ 20°C/hr, to room temperature. The annealed glass slides were washed with detergent and flowing, doubly distilled water for a period of 10 minutes o avoid surface contamination. The glass slides were finally rinsed with acetone for 5 ninutes prior to putting in an air oven. The time of drying was 20 hrs. at 120°C. Finally, the glass slides were placed in a desiccator for 24 hrs prior to application of a thin layer of Kerosene using a paint brush. Next, the melamine formaldehyde polymeric layer was applied by a hand lay-up technique. Thus, a stack of alternate glass slide, oily film and polymeric layer was developed with only 2 interfacial layers kept between the glass slides. The lamination of this stack of alternate glass slide layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 2 KPa applied at room temperature (30°C) for a period of 15 hrs. The average density value of the laminate was 2.40 gm/cc. The polymer layer had a thickness of 58.9 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multi-layer laminate in a universal testing machine and compared to that of the matrix glass slide. For the laminate, the failure energy was 10.83 J/m2 as compared to the low failure energy of 5.05 j/m2 obtained for the thin matrix glass slides. EXAMPLE-13 To fabricate glass polymer hybrid multi-layer laminates, three number of thin glass slides were obtained commercially. The dimensions were measured by a callipers. The average length was 75 mm, width 18 mm and thickness 1.01 mm. The glass slides were washed with uetergent and flowing, doubly distilled water for a period of 5 minutes to avoid surface contamination. The glass slides were finally rinsed with acetone for 15 minutes prior to putting in an air oven. The time of drying was 15 hrs. at 100°C. Finally, the glass disks were placed in a desiccator for 24 hrs prior to application of a thin layer of Kerosene using a paint brush. Next, the polyvinyl butyral polymeric layer was applied by a spray gun. Thus, a stack of alternate glass slide, oily film and polymeric layer was developed with only 2 interfacial layers kept between the glass slides. The lamination of this stack of alternate glass disk layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 6 KPa applied at room temperature (30°C) for a period of 10 hrs. The average density value of the laminate was 2.40 gm/cc. The polymer layer had a thickness of 21.8 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multi-layer laminate in a universal testing machine and compared to that of the matrix glass slide. For the laminate, the failure energy was 16.63 J/m2 as compared to the low failure energy of 5.05 J/m2 obtained for the thin matrix glass slides. EXAMPLE-14 To fabricate glass polymer hybrid multi-layer laminates, three number of thin glass slides were obtained commercially. The glass used was a borosilicate glass. The dimensions were measured by a callipers. The average length was 75 mm, width 25 mm and the thickness 1.17 mm. The annealing schedule followed for the glass slides was as follows : heating from room temperature to 500°C @ 100°C/hr followed by a soak of 1.2 hour at 500°C and cooling down from 500°C temperature @ 5°C/hr to 320°C and then finally cooling from 320°C, @ 20°C/hr, to room temperature. The annealed glass slides were washed with detergent and flowing, doubly distilled water for a period of 20 minutes to avoid surface contamination. The glass slides were finally rinsed with acetone for 15 minutes prior to putting in an air oven. The time of drying was 10 hrs. at 100°C. Finally, the glass slides were placed in a desiccator for 24 hrs prior to application of a thin layer of Kerosene using a paint brush. Next, the polyvinyl ester polymeric layer was applied by a hand lay-up technique. Thus, a stack of alternate glass slide, oily film and polymeric layer was developed with only 2 interfacial layers kept between the glass slides. The lamination of this stack of alternate glass slide layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 8 KPa applied at room :emperature (30°C) for a period of 10 hrs. The average density value of the laminate was 139 gm/cc. The poiymer layer had a thickness of 89.6 micron. Finally, the failure resistance was measured for these glass-polymer nybnd multi-layer laminate in a universal testing machine and compared to that of the matrix glass slide. For the laminate, the failure energy was 25.44 J/m2 as compared to the low failure energy of 4.63 J/m2 obtained for the thin matrix glass slides. EXAMPLE-15 To fabricate glass poiymer hybrid multi-layer laminates, three number of thin glass slides were obtained commercially. The dimensions were measured by a callipers. The average length was 75 mm, width 25 mm and thickness 1.17 mm. The glass slides were washed with detergent and flowing, doubly distilled water for a period of 15 minutes to avoid surface contamination The glass slides were finally rinsed with acetone for 10 minutes prior to putting in an air oven. The time of drying was 20 hrs. at 120°C. Finally, the glass slides were placed in a desiccator for 36 hrs prior to application of a thin layer of Kerosene using a spray gun. Next, the polyamide polymeric layer was applied by a hand lay-up technique. Thus, a stack of alternate glass slide, oily film and polymeric layer was developed with only 2 interfacial layers kept between the glass slides. The lamination of this stack of alternate glass slide layer and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 6 KPa applied at room temperature (30°C) for a period of 15 hrs. The average density value of the laminate was 2.43 gm/cc. The polymer layer had a thickness of 51.8 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multi-layer laminate in a universal testing machine and compared to that of the matrix glass slide. For the laminate, the failure energy was 24.39 J/m2 as compared to the low failure energy of 5.05 J/m2 obtained for the thin matrix glass slides. n the present invention there is provided an improved process for the fabrication of glass-ooiymer nybrid multi-layer laminates having the novelty of enhanced resistance to aiiure. This has been achieved by the non-obvious inventive step of providing lamination of a plurality of alternate glass, especially an intermediate oily interfaciai film and a ooiymeric layer at low pressure at room temperature. This inventive step of introducing an oily film provides controlled debonding crack growth at the interface to be realised in practice, in addition, the lamination at low pressure and room temperature results in a weak interfaciai bonding between the plurality of glass and polymer layers, more particularly so due to the presence of the oily film which makes strong cohesion difficult to be achieved at the interface. For instance, even the glass-polymer hybrid 2-layer laminate with a thin interfaciai kerosene film along with epoxy polymeric layer reinforced with an additional woven E-glass fabric exhibit failure energy value of as high as 159.84 J/m2 which is much higher than the low failure energy of 5.03 J/rn^ obtained for the thin matrix glass sheets. In absence of the thin interfaciai kerosene film, similar glass polymer hybrid 2-layer laminates of identical architectural design exhibit failure energy value of only 39.45 J/rrr'. This weak interfaciai bonding brings about controlled debonding when the glass-polymer hybrid multi-layer laminate is subjected to stress. This controlled debonding results in stepped load deformation behavior, thus providing enhanced resistance to failure. It has been demonstrated herein indeed by the way of examples that depending on the type of oily film, nature of reinforcement and the number of reinforcing layers, the failure resistance of the glass polymer hybrid multi-layer composites can be indeed be enhanced to a value of as high as about 1341 J/m2 in comparison to a low value of about 5 J/m2 obtained for the brittle glass matrix. Similarly, on the lower side values as small as about 10 J/m2 could also be obtained for the failure resistance of the glass polymer hybrid multi-layer composites, depending on the nature of oily film, the type of reinforcement, the number of reinforcing layers and the relative thickness of reinforcing layers. This demonstrates that the present process provides a means to tailor the failure resistance of the glass polymer hybrid multi-layer composites to suit a chosen end application. "he man advantages of the present process are : it provides an improved means for the fabrication of giass-poiymer hybrid multi-layer ammates with enhanced failure resistance. -.. Another advantage of the present invention is that it has made the process for the fabrication of glass-polymer hybrid multi-layer laminates much simpler than the earlier process. 3. Still another advantage of the present invention is that it has made the process for the abrication of glass-polymer hybrid multi-layer laminates more cost effective than the -?arlier process. 4 Yet another advantage of the present invention is that it provides means to tailor the fabrication procedure of the glass-polymer hybrid multi-layer laminates in terms of the choice of polymeric layer, choice of the oily film at interface to achieve a controllable degree of weakness at the interface, choice of the number of interfacial layers and laminating pressure so that the desired failure resistance to suit a particular end application can be attained. We claim : 1. An improved process for the manufacture of glass - polymer hybrid multi-layer laminates having enhanced failure resistance which comprises cleaning glass substrates by known methods, drying the cleaned glass substrates followed by coating the said cleaned and dried glass substrates with an oily film, over the said oily film coating applying a polymeric layer of thickness in the range of 22-360 µm to obtain oily film and polymer coated glass substrates, optionally providing layer of reinforcing material over the said coated glass substrates, making a stack of plurality of said coated glass substrates, laminating the said stack so obtained under uniaxial pressure in the range of 2-10 KPa at room temperature for a period in the range of 10-15 hrs. 2. An improved process as claimed in claim 1, wherein the glass used is such as unannealed / annealed soda lime silica glass, borosilicate glass or aluminosilicate glass. 3. An improved process as claimed in claim 1-2, wherein the thickness of the glass sheets and slides used is in the range of 0.3 to 1.17 mm. 4. An improved process as claimed in claim 1-3, wherein the oily interfacial film is such as kerosene, gasoline, n-Heptadecane, n - Nonadecane. 5. An improved process as claimed in claim 1-4, wherein the polymer used is such as a thermosetting epoxy resin, phenolic resins, melamine formaldehyde resin, silicone resins. 6. An improved process as claimed in claim 1-5, wherein the polymer used is such as a thermoplastic polyvinyl butyral resin, polyvinyl ester, polyamide. 7. An improved process as claimed in claim 1-6, wherein interfacial layers of woven e-glass fabric or rovings are provided along with polymeric layers. 8. An improved process as claimed in claim 1-7, wherein a polymeric layer is provided over the optional layer of reinforcing material. 9. A Glass - polymer hybrid multi-layer laminates having enhanced failure resistance made by the process as claimed in claims 1-8. 10. An improved process for the manufacture of glass - polymer hybrid multi-layer laminates having enhanced failure resistance, substantially as herein described with reference to the examples.

Full Text

The present invention relates to an improved process for the manufacture of glass -polymer hybrid multi-layer laminates having enhanced failure resistance and glass -oolymer hybrid multi-layer laminates made thereby.
The main usage of this hybrid multi-layer laminate structure is as aamage tolerant natenal that can sustain stress even after onset of fracture. Yet another application is as structural material for load bearing engineering applications. The other important application is as opaque window pane. Another major application is as artificial separators used with wooden or aluminium frames as space dividers for interior decoration.
Reference may be made to US Patent no. 5,972,819 (1999) wherein a damage tolerant material was disclosed t,: be a multi-layer structure comprising of a top layer of 85-90% dense cylindrical alumina pellets arranged in a plurality of adjacent rows backed up by a laminate comprising of layers of a plurality of adjacent layers comprising of a plurality of unidirectional fibers embedded in a polymeric matrix where the fibers of adjacent layers must lie at an angle of between 45 degree to 90 degree. It was mentioned that the convexly faced surface of the cylindrical pellets must be directed towards the outer surface of the top facing plate, thus making the process complicated in terms of ease of fabrication. Also there is a severe size restriction that the ratio of diameter (D) to the radius of curvature ( R ) of the curved surface of cylindrical pellets must lie in the range D/R = 0.64:1 to 0.85 : 1, thus making the process less flexible in terms of the choice of material. Further, the use of synthetic fibers make the process less cost effective.
Reference may also be made to US Patent no. 6,112,635 (2000) wherein a damage tolerant multi-layer structure has been disclosed to be comprised of plurality of adjacent rows of alumina pellets embedded in aluminium or a thermoplastic resin or a thermosetting resin backed up by tough woven textile material followed by a back up layer of aluminium. There is a severe size restriction that the alumina pellets must be at least 12 mm in length and must be in contact with at least 4 adjacent pellets, thus making 'he process complicated in terms of ease of fabrication. The use of tough woven textile fabrics eg. Aramid fibers or polyamide netting has made the process less cost effective. Further back up layer of aluminium addition makes the process step-wise more lengthier.
Reference may also be made to US patent no. 6, 332, 390 (2001) wherein a 0.75 inch to 0.815 inch thick multi-layer damage tolerant structure is disclosed to be comprised of a 0.25 inch thick aramid fiber reinforced polymer matrix laminate facing material backed up by 0.32 inch thick alumina or silicon carbide or boron carbide ceramic tile based second layer followed by 0.06 inch to 0.125 inch thick third layer of glass or ceramic overlay strips used for protection of tile joint and free edge areas, backed up by 0.03 inch thick aramid spall shield. The fabrication process is quite complicated, involves stringent control of individual layer thickness and the use of aramid fibers and aramid nettings make the process less cost effective.
Reference may also be made to or co-pending Indian patent application no. 51/DEL/2002 (232797) dt 21-12-2002 wherein we have described and claimed a simple yet cost-effective process for the manufacture of glass-polymer hybrid multi-layer laminates having improved failure resistance and glass-polymer hybrid multi-layer laminates made thereby. The clue to obtaining improvement in failure resistance was found to be linked to the achievement of controlled interfacial de-bonding leading to the growth of delamination cracks through the multi-layer composite architecture that involved alternate placement of a plurality of brittle and strong layers with a weak interface between the two. However, the maximum improvement of failure resistance was limited to only a value of about 270 J/m2.
Reference may also be made to an article published in the Journal of the American Ceramic Society, vol. 77, no.8, pp.2081-2087, 1994, wherein glass sheets or slides were used as the matrix material in between alternate interfacial layers of a reinforcing polymer (ie. polyvinyl butyral, a thermoplastic resin) to fabricate the glass-polymer multilayer structure with a maximum of only 5 interfacial layers. The stack of the plurality of alternate glass and polymer layers sealed under vacuum in a specially made envelop, was vacuum hot pressed for three minutes at a high temperature of 175°C under a high uniaxial pressure of 350 KPa, thus making the process stepwise complicated as well as costlier. In addition, the very not pressing technique used for the fabrication technique gave rise to more of strong bonding between the layers, thus causing the material to behave in a more orittle like fashion. Further, no assessment of the failure resistance of the glass-polymer multi-layer composites fabricated by vacuum hot pressing was done. Thus, the major drawbacks of the hitherto known processes are that they are complicated, costlier and the "abrication technique gives rise to strong interfacial bonding.
The main object of the present invention is to provide an improved process for the manufacture of glass - polymer hybrid multi-layer laminates having enhanced failure resistance.
Another object of the present invention is to provide an improved process for the manufacture of glass-polymer hybrid multi-layer laminates, which is cost effective.
Yet another object of the present invention is to provide an improved process to tailor the manufacture procedure of the glass-polymer hybrid multi-layer laminates in terms of the choice of polymeric layer, choice of the number of interfacial layers, laminating pressure so that failure resistance to suit a given end application can be attained.
Still another object is to provide a glass-polymer hybrid multi-layer laminates having improved failure resistance.
In the present invention, an improved process has been provided to obtain glass polymer hybrid multi-layer laminates with enhanced failure resistance. The enhancement in failure resistance was made possible through controlled interfacial debonding leading to the growth of delamination cracks. The architecture of the multi-layer composite involved alternate placement of a plurality of brittle glass and viscoelastic polymeric layers with a deliberately designed weak interface between the two. In particular the desired variation in the degree of weakness was achieved by the innovative introduction of a thin oily film at the interface between the glass la nd the polymeric layer. In addition, the advantage of the low pressure lamination tecnnique was exploited to further develop the weakness of the interface. This makes the process not only simpler but also cost effective. It has been shown further that depending on the type of oily film, type of reinforcement and the number of reinforcing layers, the failure resistance of the glass polymer hybrid multi-layer composites can be enhanced to a value of as high as about 1341 J/m2 in comparison to a low value of about 5 J/m2 obtained for the brittle glass matrix. Similarly, on the lower side values as small as about 10 J/m2 could also be obtained for the failure resistance of the glass polymer hybrid multi-layer composites, depending on the type of oily film, the type of reinforcement and the number of reinforcing layers. In other words, thus, the present process provides a means to tailor the failure resistance of the glass polymer hybrid multi-layer composites to suit a particular end application.
Accordingly, the present invention provides an improved process for the manufacture of glass - polymer hybrid multi-layer laminates having enhanced failure resistance which comprises cleaning glass substrates by known methods, drying the cleaned glass substrates followed by coating the said cleaned and dried glass substrates with an oily film, over the said oily film coating applying a polymeric layer of thickness in the range of 22-360 µm to obtain oily film and polymer coated glass substrates, optionally providing layer of reinforcing material over the said coated glass substrates, making a stack of plurality of said coated glass substrates, laminating the said stack so obtained under uniaxial pressure in the range of 2-10 KPa at room temperature for a period in the range of 10-15 hrs.
In an embodiment of the present invention the glass used is such as unannealed / annealed soda lime silica glass, borosilicate glass, aluminosilicate glass.
In another embodiment of the present invention the thickness of the glass sheets and slides of thickness is in the range of 0.3 -1.17 mm.
In still another embodiment of the present invention the cleaning of the glass substrates is done by washing with detergent solution followed by water for a period in the range of 10
to 2. hinutes. n vet another embodiment of the present invention the rinsing or the glass substrates is lone by rinsing with acetone for a period in the range of 5 to 15 minutes.
i still yet another embodiment of the present invention the arying or the cleaned and nnsed glass substrates is done for a period in the range of 10 to20 hours at a temperature n the range of 80 to 120°C.
in a further embodiment of the present invention interfacial layers of oily film is such as Kerosene, gasolene, n-Heptadecane, n-Nonadecane.
!n a still further embodiment of the present invention the polymer is a thermosetting resin such as epoxy resins, phenolic resins, melamine formaldehyde resin, siiicone resins.
in another embodiment of the present invention the polymer is a thermoplastic resin such as polyvinyi butyral, polyvinyl ester, polyamide.
In yet another embodiment of the present invention the reinforcing material is such as woven E -glass fabric, roving.
In still another embodiment of the present invention a polymeric layer is provided over the optional layer of reinforcing material.
Accordingly, the present invention provides glass - polymer hybrid multi-layer laminates having enhanced failure resistance made by the process of the present invention as described herein.
The non-obvious inventive step to achieve the novelty of improved failure resistance of the glass polymer hybrid multi-layer laminates lies in the achievement of controlled debonding through the use of a thin oily film at the interface. The present glass polymer •brid multi-layer laminates are provided with an alternate brittle-strong architecture naving a deliberately introduced weak interfacial bonding between the brittle layer and the
strong layer. The weak interfaciai bonding is a consequence of (a) the oily film provided curing fabrication and (b) the low pressure lamination techniaue applied at room emperature. Particularly the presence of the oily film makes ;he strong interfacial ;onesion aifficuil to oe acrneved. Because the interfacial bonding ,s deliberately kept weak, as the onttle glass layer fails, the interfacial polymeric layer takes up the load and then, a local delamination crack ensues at the interface when the reinforcing layer takes up the load. On continued loading, this reinforcing layer breaks up eventually when the next brittle layer takes up the load again. The continuation of this process gives rise to a process of controlled debonding manifested as a stepped load deflection behaviour of the glass polymer hybrid multi-layer laminates, which, in the process, consume much higher amount of strain energy from the loading system thus, enhancing their own failure energy values manifold over that of the corresponding glass matrix layers. In contrast to this pseudo-ductile nature of load deformation behavior in the glass polymer hybrid multi-layer laminates, the brittle glass matrix shows a characteristic fast fracture behavior and hence a much lower value of failure energy. In the prior art damage tolerant multi-layer structures were developed by using either dense ceramic bodies of particular geometry and size embedded in metallic or polymeric matrix with or without a backing up layer of tough woven textile fabrics based laminate occasionally having support of a further backing up layer of light metallic materials thus, making the processes complicated in terms of ease of fabrication and less cost effective because of the utilization of cost intensive synthetic fibers. Also, in the prior art attempts were made to develop glass -polymer multi-layer structures with a stack of plurality of alternate glass and polymer layers vacuum sealed and vacuum hot pressed for three minutes at a high temperature of 175°C under a high uniaxial pressure of 350 KPa, which reduced second phase to a volume fraction of only 0.01. This is so because most of the resin had flown out at high temperature and pressure of hot pressing. Thus the earlier work had the drawbacks of involving complicated steps, cost ineffectiveness and possibility of strong interfacial bonding. In the present invention these drawbacks are obviated through the provision of a simpler and much less costlier process for the fabrication of glass-polymer hybrid multilayer laminates having the novelty of improved resistance to failure. This was achieved by the non-obvious inventive step of providing an oily interfacial film during the process of
low pressure lamination of a plurality of alternate glass and a polymeric layer at room 'emperature. This inventive step of presence of a oily film deterring interfacial cohesion along with the technique of lamination at low pressure and room temperature caused a A/eak interfaciai bonding between the plurality of glass and polymer layers. This weak intertacial bonding promoted more of controlled debonding when the glass-polymer hybrid multi-layer laminate was subjected to stress. This controlled debonding led to a stepped :oad deformation behaviour, thus providing improved resistance to failure.
The details of the process steps of the present invention are:
1. Annealed/unannealed glass sheets and slides of thickness in the range of 0.3-1.17
mm are washed with detergent solution followed by water for 10-20 mins.
2. Washed glass sheets and slides are rinsed with acetone for 5-15 minutes.
3. Rinsed glass sheets and slides are dried for 10-20 hrs at 80-120°C in air.
4. Dried glass sheets and slides are kept in a desiccator for 12-36 hrs. at room
temperature.
5. Oily Film is applied by conventional means on one side of glass sheets and slides.

6. Polymeric layer of thickness « 22-360 jam thickness is applied by conventional
methods on one side of the glass sheets and a stack of plurality of alternate glass,
oily film and polymer layer is made. Optionally, an additional layer of woven e-
glass fabric or roving may be provided along with a polymeric coating.
7. The stack of material obtained in step 5 is laminated in a laboratory press under a
uniaxial pressure of 2-10 KPa at room temperature (25-33°C) for a period of 10-15
hrs. to obtain the glass-polymer hybrid multilayer laminates.The following examples are given by way of illustration ana therefore should not be construed to limit the scope of the present invention.
EXAMPLE-1
ro fabricate glass polymer hybrid multi-layer laminates, eleven numbers of thin square glass sheets was obtained commercially. The glass was a soda lime silica glass. The ength. breadth and thickness was measured by callipers. The average dimension was 18 mm and thickness 0.3 mm. The square glass sheets were washed with detergent solution •nci flowing, doubly distilled water for a period of 20 minutes. The glass sheets were mally rinsed with acetone for 15 minutes prior to putting in an air oven. The time of drying was 18 hrs. at 100°C. Finally, the glass sheets were placed in a desiccator for 12 hrs prior to application of the epoxy polymeric layer and a E-glass woven fabric by a hand lay-up technique. Thus, a plurality of stack of alternate glass sheet and polymeric layer was neveloped with ten interfacial epoxy layer kept between the glass disks. The lamination of this stack of plurality of alternate glass plate layer and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 2 KPa applied at room temperature (25°C) for a period of 10 hrs. The average density of the laminate was 1.80 gm/cc. The polymer layer had a thickness of 258 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multilayer laminates in a universal testing machine and compared to that of the matrix glass disk. For the laminate, the failure energy was 164 J/m2 as compared to the low failure energy of 5.03 J/m2 obtained for the thin matrix glass sheets.
EXAMPLE-2
To fabricate glass polymer hybrid multi-layer laminates, two number of thin circular glass disks was obtained commercially. The diameter and thickness were measured by a callipers. The average diameter was 18 mm and thickness 0.3 mm. The alass discs were vashfcu with detergent and flowing, aouoly distilled water for a period or 15 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 10 minutes prior to putting in an air oven. The time of drying was 15 hrs. at 120°C. Finally, the glass disks were placed in a desiccator for 24 hrs prior to application of a thin layer of kerosene using a spray gun. Next, the epoxy polymeric layer was placed by using a paint brush along with the placement of a woven E-glass fabric cloth for reinforcement. Thus, a stack of alternate glass disk, oily film, polymeric layer reinforced with woven fabric was developed with only 1 interfacial epoxy layer kept between the glass disks. The lamination of this stack of alternate glass disk layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 4 KPa applied at room temperature (30°C) for a period of 15 hrs. The average density value of the laminate was 2.04 gm/cc. The polymer layer had a thickness of 360 micron. Finally, the failure resistance was measured for these glass-pclymer hybrid multi-layer laminate in a universal testing machine and compared to that of the matrix glass disk. For the laminate, the failure energy was 159.84 J/m2 as compared to the low failure energy of 5.03 J/m2 obtained for the thin matrix glass disks.
EXAMPLE-3
To fabricate glass polymer hybrid multi-layer laminates, two number of thin circular glass disks was obtained commercially. The diameter and thickness were measured by a callipers. The average diameter was 18 mm and thickness 0.3 mm. The glass discs were washed with detergent and flowing, doubly distilled water for a period of 20 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 5 minutes prior to putting in an air oven. The time of drying was 15 hrs. at 110°C. Finally, the glass disks were placed in a desiccator for 12 hrs prior to application of the epoxy polymeric layer by using a paint brush along with the placement of a E-glass fabric for reinforcement. Thus, a stack of alternate glass disk and polymeric layer was developed with only 1 interfacial epoxy layer reinforced with woven glass cloth kept between the glass disks. The lamination of this stack of alternate glass disk layer and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 6 KPa applied at room temperature (30°C) for a period of 10 hrs. The average density value of
:he laminate was 2.03 gm/cc. The polymer layer had a thickness or 358.9 micron. Finally, :he failure resistance was measured for these glass-polymer hybrid multi-layer laminate in a universal testing machine and compared to that of the matrix giass disk. For the aminate, the failure energy was 39.45 J/rrr as compared to the low railure energy of 5.03 J/rrr obtained for the thin matrix glass disks.
EXAMPLE - 4
To fabricate glass polymer hybrid multi-layer laminates, eleven number of thin circular giass disks was obtained commercially. The diameter and thickness were measured by a callipers. The average diameter was 18 mm and thickness 0.3 mm. The glass discs were washed with detergent and flowing, doubly distilled water for a period of 20 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 10 minutes prior to putting in an air oven. The time of drying was 36 hrs. at 120°C. Finally, the glass disks were placed in a desiccator for 24 hrs prior to application of a thin film of kerosene by using a paint brush. Next, the epoxy polymeric layer was applied by a hand lay-up technique along with the placement of a E-glass fabric for reinforcement. Thus, a stack of alternate glass disk, oily film and polymeric layer reinforced with woven glass cloth was developed with ten interfacial epoxy layers kept between the glass disks. The lamination of this stack of alternate glass disk layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 10 KPa applied at room temperature (30°C) for a period of 15 hrs. The average density value of the laminate was 2.01 gm/cc. The polymer layer had a thickness of 260 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multilayer laminate in a universal testing machine and compared to that of the matrix glass disk. For the laminate, the failure energy was 1340.66 J/m2 as compared to the low failure energy of 5.03 J/m2 obtained for the thin matrix glass disks.

EXAMPLE -5
To fabricate glass polymer hybrid multi-layer laminates, eleven number of thin circular glass disks was obtained commercially. The diameter and thickness were measured by a callipers. The average diameter was 18 mm and thickness 0.3 mm. The glass discs were washed with detergent and flowing, doubly distilled water for a period of 5 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 10 minutes prior to putting in an air oven. The time of drying was 12 hrs. at 120°C. Finally, the glass disks were placed in a desiccator for 24 hrs prior to application of the epoxy polymeric layer by using a paint brush along with the placement of a E-glass fabric for reinforcement. Thus, a stack of alternate glass disk and polymeric layer reinforced with woven glass cloth was developed with ten interfacial epoxy layers kept between the glass disks. The lamination of this stack of alternate glass disk layer and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 8 KPa applied at room temperature (30°C) for a period of 12 hrs. The average density value of the laminate was 2.01 gm/cc. The polymer layer had a thickness of 261.8 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multilayer laminate in a universal testing machine and compared to that of the matrix glass disk. For the laminate, the failure energy was 347.05 J/m2 as compared to the low failure energy of 5.03 J/m2 obtained for the thin matrix glass disks.
EXAMPLE - 6
To fabricate glass polymer hybrid multi-layer laminates, two number of thin circular glass disks was obtained commercially. The diameter and thickness were measured by a callipers. The average diameter was 18 mm and thickness 0.3 mm. The glass discs were washed with detergent and flowing, doubly distilled water for a period of 20 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 15 minutes prior to putting in an air oven. The time of drying was 24 hrs. at 110°C. Finally, the glass disks were placed in a desiccat 24 hrs prior to application of a thin layer of Heptadecane by using a hand spray gu, jext, the epoxy polymeric layer was applied
using a paint brush along with the placement of a t-glass fabric for reinforcement. ""hus. a stack of alternate glass disk, oily film and polymeric layer reinforced with woven :jiass cloth was developed with only 1 interfacial epoxy layer kept between the glass 3isks. The lamination of this stack of alternate giass disk layer, oily film and polymeric iayer was done in a conventional laboratory press under a low uniaxial pressure of 4 KPa applied at room temperature (30°C) for a period of 10 hrs. The average density value of ihe laminate was 2.03 gm/cc. The polymer layer had a thickness of 354 micron. Finally, rhe failure resistance was measured for these glass-polymer hybrid multi-layer laminate in a universal testing machine and compared to that of the matrix glass disk. For the iaminate, the failure energy was 153.69 J/m2 as compared to the low failure energy of :.03 J/m2 obtained for the thin matrix glass disks.
EXAMPLE - 7
To fabricate glass polymer hybrid multi-layer laminates, two number of thin circular glass disks was optamed commercially. The diameter was measured by a callipers. Using the same instrument, the thickness of the disks was measured. The average diameter was 18 mm and thickness 0.3 mm. The glass discs were washed with detergent and flowing, doubly distilled water for a period of 10 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 10 minutes prior to putting in an air oven. The time of drying was 12 hrs. at 80°C. Finally, the glass disks were placed in a desiccator for 24 hrs prior to application of a thin film of n-Octadecane by a hand spray gun. Next, the epoxy polymeric layer was applied by using a paint brush along with the placement of a E-giass fabric for reinforcement. Thus, a stack of alternate glass disk, oily film and polymeric layer reinforced with woven glass cloth was developed with only 1 interfacial epoxy layer kept between the glass disks. The lamination of this stack of alternate glass disk layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 2 KPa applied at room temperature (30°C) for a period of 10 hrs. The average density value of the laminate was 2.04 grn/cc. The polymer layer had a thickness of 359.2 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multi-layer laminate in a universal testing machine ana compared to that
of the matrix glass disk. For the laminate, the failure energy was 145.22 J/m2 as compared to the low failure energy of 5.03 J/m" obtained for the thin -natnx glass disks.
EXAMPLE - 3
To fabricate glass polymer hybrid multi-layer laminates, two number of thin circular glass disks was obtained commercially. The diameter and thickness were measured by a callipers. The average diameter was 18 mm and thickness 0.3 mm. The glass discs were washed with detergent and flowing, doubly distilled water for a period of 5 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 15 minutes prior to putting in an air oven. The time of drying was 18 hrs. at 120°C. Finally, the glass disks were placed in a desiccator for 24 hrs prior to application of a thin film of n-Nonadecane using a hand spray gun. Next, the epoxy polymeric layer was applied by using a paint brush along with the placement of a E-glass fabric for reinforcement. Thus, a stack of alternate glass disk, oily film and polymeric layer reinforced with woven glass cloth was developed with only 1 interfacial epoxy layer kept between the glass disks. The lamination of this stack of alternate glass disk layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 4 KPa applied at room temperature (30°C) for a period of 10 hrs. The average density value of the laminate was 2.02 gm/cc. The polymer layer had a thickness of 362.3 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multi-layer laminate in a universal testing machine and compared to that of the matrix glass disk. For the laminate, the failure energy was 161.71 J/m2 as compared to the low failure energy of 5.03 J/m2 obtained for the thin matrix glass disks.
EXAMPLE - 9
To fabricate glass polymer hybrid multi-layer laminates, two number of thin circular glass disks was obtained commercially. The diameter and thickness were measured by callipers. The average diameter was 18 mm and thickness 0.3 mm. The circular glass jiscs were washed with detergent and flowing, doubly distilled water for a period of 10
minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 5 minutes prior to putting in an air oven. The time of drying was 15 hrs. at 100°C. Finally, the glass disks were placed in a desiccator for 24 hrs prior to application of a thin layer of n-lcosane by a hand spray gun. Next, the epoxy polymeric layer was applied by using a paint brush along with the placement of a E-glass fabric for reinforcement. Thus, a stack of alternate glass disk, oily film and polymeric layer was developed with only 1 interfacial epoxy layer kept between the glass disks. The lamination of this stack of alternate glass disk layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 3 KPa applied at room temperature (30°C) for a period of 10 hrs. The average density value of the laminate was 2.03 gm/cc. The polymer layer had a thickness of 358.4 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multi-layer laminate in a universal testing machine and compared to that of the matrix glass disk. For the laminate, the failure energy was 158.62 J/m2 as compared to the low failure energy of 5.03 J/m2 obtained for the thin matrix glass disks.
EXAMPLE-10
To fabricate glass polymer hybrid multi-layer laminates, two number of thin circular glass disks was obtained commercially. The diameter and thickness were measured by a callipers. The average diameter was 18 mm and thickness 0.3 mm. The glass discs were washed with detergent and flowing, doubly distilled water for a period of 15 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 10 minutes prior to putting in an air oven. The time of drying was 12 hrs. at 90°C. Finally, the glass disks were placed in a desiccator for 24 hrs prior to application of a thin layer of n-Henicosane using a hand spray gun. Next, the silicone resin polymeric layer was applied by using a paint brush along with the placement of a E-glass roving for reinforcement. Thus, a stack of alternate glass disk, oily film and polymeric layer reinforced with woven glass cloth was developed with only 1 interfacial epoxy layer kept between the glass disks. The lamination of this stack of alternate glass disk layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 6 KPa
applied at room temperature (30°C) for a period of 12 hrs. The average density value of :he laminate was 2.03 gm/cc. The polymer layer had a thickness of 359.6 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multi-layer laminate in 3 universal testing machine and compared to that o* the matrix glass disk. For the laminate, the failure energy was 168.35 J/m2 as compared to the low failure energy of 5.03 J/m^ obtained for the thin matrix glass disks.
EXAMPLE-11
To fabricate glass polymer hybrid multi-layer laminates, two number of thin circular glass disks was obtained commercially. The diameter and thickness were measured by a callipers. The average diameter was 18 mm and thickness 0.3 mm. The glass discs were washed with detergent and flowing, doubly distilled water for a period of 5 minutes to avoid surface contamination. The glass discs were finally rinsed with acetone for 10 minutes prior to putting in an air oven. The time of drying was 36 hrs. at 120°C. Finally, the glass disks were placed in a desiccator for 24 hrs prior to application of a thin layer of Gasolene by a hand spray gun. Next, the phenolic resin polymeric layer was applied by using a hand lay-up technique along with the placement of a E-glass fabric for reinforcement. Thus, a stack of alternate glass disk, oily film and polymeric layer was developed with only 1 interfacial epoxy layer kept between the glass disks. The lamination of this stack of alternate glass disk layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 2 KPa applied at room temperature (30°C) for a period of 12 hrs. The average density value of the laminate was
2.2 gm/cc. The polymer layer had a thickness of 358.7 micron. Finally, the failure
resistance was measured for these glass-polymer hybrid multi-layer laminate in a
universal testing machine and compared to that of the matrix glass disk. For the
laminate, the failure energy was 153.58 J/m2 as compared to the low failure energy of
5.2 J/m2 obtained for the thin matrix glass disks.

EXAMPLE- 12
"o fabricate glass polymer hybrid multi-layer laminates, three number of thin glass slides vas obtained commercially. The glass used was an aluminosilicate glass. The dimensions were measured by a callipers. The average length was 75 mm, width 18 mm and thickness 1.01 mm. The annealing schedule followed for the glass slides was as rollows : heating from room temperature to 520°C @ 100°C/hr followed by a soak of 1 hour at 520°C and cooling down from 520°C temperature @ 5°C/hr to 300°C and then *inally cooling from 300°C, @ 20°C/hr, to room temperature. The annealed glass slides were washed with detergent and flowing, doubly distilled water for a period of 10 minutes o avoid surface contamination. The glass slides were finally rinsed with acetone for 5 ninutes prior to putting in an air oven. The time of drying was 20 hrs. at 120°C. Finally, the glass slides were placed in a desiccator for 24 hrs prior to application of a thin layer of Kerosene using a paint brush. Next, the melamine formaldehyde polymeric layer was applied by a hand lay-up technique. Thus, a stack of alternate glass slide, oily film and polymeric layer was developed with only 2 interfacial layers kept between the glass slides. The lamination of this stack of alternate glass slide layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 2 KPa applied at room temperature (30°C) for a period of 15 hrs. The average density value of the laminate was 2.40 gm/cc. The polymer layer had a thickness of 58.9 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multi-layer laminate in a universal testing machine and compared to that of the matrix glass slide. For the laminate, the failure energy was 10.83 J/m2 as compared to the low failure energy of 5.05 j/m2 obtained for the thin matrix glass slides.
EXAMPLE-13
To fabricate glass polymer hybrid multi-layer laminates, three number of thin glass slides were obtained commercially. The dimensions were measured by a callipers. The average length was 75 mm, width 18 mm and thickness 1.01 mm. The glass slides were washed with uetergent and flowing, doubly distilled water for a period of 5 minutes to avoid
surface contamination. The glass slides were finally rinsed with acetone for 15 minutes prior to putting in an air oven. The time of drying was 15 hrs. at 100°C. Finally, the glass disks were placed in a desiccator for 24 hrs prior to application of a thin layer of Kerosene using a paint brush. Next, the polyvinyl butyral polymeric layer was applied by a spray gun. Thus, a stack of alternate glass slide, oily film and polymeric layer was developed with only 2 interfacial layers kept between the glass slides. The lamination of this stack of alternate glass disk layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 6 KPa applied at room temperature (30°C) for a period of 10 hrs. The average density value of the laminate was 2.40 gm/cc. The polymer layer had a thickness of 21.8 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multi-layer laminate in a universal testing machine and compared to that of the matrix glass slide. For the laminate, the failure energy was 16.63 J/m2 as compared to the low failure energy of 5.05 J/m2 obtained for the thin matrix glass slides.
EXAMPLE-14
To fabricate glass polymer hybrid multi-layer laminates, three number of thin glass slides were obtained commercially. The glass used was a borosilicate glass. The dimensions were measured by a callipers. The average length was 75 mm, width 25 mm and the thickness 1.17 mm. The annealing schedule followed for the glass slides was as follows : heating from room temperature to 500°C @ 100°C/hr followed by a soak of 1.2 hour at 500°C and cooling down from 500°C temperature @ 5°C/hr to 320°C and then finally cooling from 320°C, @ 20°C/hr, to room temperature. The annealed glass slides were washed with detergent and flowing, doubly distilled water for a period of 20 minutes to avoid surface contamination. The glass slides were finally rinsed with acetone for 15 minutes prior to putting in an air oven. The time of drying was 10 hrs. at 100°C. Finally, the glass slides were placed in a desiccator for 24 hrs prior to application of a thin layer of Kerosene using a paint brush. Next, the polyvinyl ester polymeric layer was applied by a hand lay-up technique. Thus, a stack of alternate glass slide, oily film and polymeric layer was developed with only 2 interfacial layers kept between the glass slides. The lamination

of this stack of alternate glass slide layer, oily film and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 8 KPa applied at room :emperature (30°C) for a period of 10 hrs. The average density value of the laminate was 139 gm/cc. The poiymer layer had a thickness of 89.6 micron. Finally, the failure resistance was measured for these glass-polymer nybnd multi-layer laminate in a universal testing machine and compared to that of the matrix glass slide. For the laminate, the failure energy was 25.44 J/m2 as compared to the low failure energy of 4.63 J/m2 obtained for the thin matrix glass slides.
EXAMPLE-15
To fabricate glass poiymer hybrid multi-layer laminates, three number of thin glass slides were obtained commercially. The dimensions were measured by a callipers. The average length was 75 mm, width 25 mm and thickness 1.17 mm. The glass slides were washed with detergent and flowing, doubly distilled water for a period of 15 minutes to avoid surface contamination The glass slides were finally rinsed with acetone for 10 minutes prior to putting in an air oven. The time of drying was 20 hrs. at 120°C. Finally, the glass slides were placed in a desiccator for 36 hrs prior to application of a thin layer of Kerosene using a spray gun. Next, the polyamide polymeric layer was applied by a hand lay-up technique. Thus, a stack of alternate glass slide, oily film and polymeric layer was developed with only 2 interfacial layers kept between the glass slides. The lamination of this stack of alternate glass slide layer and polymeric layer was done in a conventional laboratory press under a low uniaxial pressure of 6 KPa applied at room temperature (30°C) for a period of 15 hrs. The average density value of the laminate was 2.43 gm/cc. The polymer layer had a thickness of 51.8 micron. Finally, the failure resistance was measured for these glass-polymer hybrid multi-layer laminate in a universal testing machine and compared to that of the matrix glass slide. For the laminate, the failure energy was 24.39 J/m2 as compared to the low failure energy of 5.05 J/m2 obtained for the thin matrix glass slides.
n the present invention there is provided an improved process for the fabrication of glass-ooiymer nybrid multi-layer laminates having the novelty of enhanced resistance to aiiure. This has been achieved by the non-obvious inventive step of providing lamination of a plurality of alternate glass, especially an intermediate oily interfaciai film and a ooiymeric layer at low pressure at room temperature. This inventive step of introducing an oily film provides controlled debonding crack growth at the interface to be realised in practice, in addition, the lamination at low pressure and room temperature results in a weak interfaciai bonding between the plurality of glass and polymer layers, more particularly so due to the presence of the oily film which makes strong cohesion difficult to be achieved at the interface. For instance, even the glass-polymer hybrid 2-layer laminate with a thin interfaciai kerosene film along with epoxy polymeric layer reinforced with an additional woven E-glass fabric exhibit failure energy value of as high as 159.84 J/m2 which is much higher than the low failure energy of 5.03 J/rn^ obtained for the thin matrix glass sheets. In absence of the thin interfaciai kerosene film, similar glass polymer hybrid 2-layer laminates of identical architectural design exhibit failure energy value of only 39.45 J/rrr'. This weak interfaciai bonding brings about controlled debonding when the glass-polymer hybrid multi-layer laminate is subjected to stress. This controlled debonding results in stepped load deformation behavior, thus providing enhanced resistance to failure. It has been demonstrated herein indeed by the way of examples that depending on the type of oily film, nature of reinforcement and the number of reinforcing layers, the failure resistance of the glass polymer hybrid multi-layer composites can be indeed be enhanced to a value of as high as about 1341 J/m2 in comparison to a low value of about 5 J/m2 obtained for the brittle glass matrix. Similarly, on the lower side values as small as about 10 J/m2 could also be obtained for the failure resistance of the glass polymer hybrid multi-layer composites, depending on the nature of oily film, the type of reinforcement, the number of reinforcing layers and the relative thickness of reinforcing layers. This demonstrates that the present process provides a means to tailor the failure resistance of the glass polymer hybrid multi-layer composites to suit a chosen end application.
"he man advantages of the present process are :
it provides an improved means for the fabrication of giass-poiymer hybrid multi-layer ammates with enhanced failure resistance.
-.. Another advantage of the present invention is that it has made the process for the fabrication of glass-polymer hybrid multi-layer laminates much simpler than the earlier process.
3. Still another advantage of the present invention is that it has made the process for the abrication of glass-polymer hybrid multi-layer laminates more cost effective than the -?arlier process.
4 Yet another advantage of the present invention is that it provides means to tailor the fabrication procedure of the glass-polymer hybrid multi-layer laminates in terms of the choice of polymeric layer, choice of the oily film at interface to achieve a controllable degree of weakness at the interface, choice of the number of interfacial layers and laminating pressure so that the desired failure resistance to suit a particular end application can be attained.

We claim :
1. An improved process for the manufacture of glass - polymer hybrid multi-layer laminates having enhanced failure resistance which comprises cleaning glass substrates by known methods, drying the cleaned glass substrates followed by coating the said cleaned and dried glass substrates with an oily film, over the said oily film coating applying a polymeric layer of thickness in the range of 22-360 µm to obtain oily film and polymer coated glass substrates, optionally providing layer of reinforcing material over the said coated glass substrates, making a stack of plurality of said coated glass substrates, laminating the said stack so obtained under uniaxial pressure in the range of 2-10 KPa at room temperature for a period in the range of 10-15 hrs.
2. An improved process as claimed in claim 1, wherein the glass used is such as unannealed / annealed soda lime silica glass, borosilicate glass or aluminosilicate glass.

3. An improved process as claimed in claim 1-2, wherein the thickness of the glass sheets and slides used is in the range of 0.3 to 1.17 mm.
4. An improved process as claimed in claim 1-3, wherein the oily interfacial film is such as kerosene, gasoline, n-Heptadecane, n - Nonadecane.
5. An improved process as claimed in claim 1-4, wherein the polymer used is such as a thermosetting epoxy resin, phenolic resins, melamine formaldehyde resin, silicone resins.
6. An improved process as claimed in claim 1-5, wherein the polymer used is such as a thermoplastic polyvinyl butyral resin, polyvinyl ester, polyamide.
7. An improved process as claimed in claim 1-6, wherein interfacial layers of woven e-glass fabric or rovings are provided along with polymeric layers.
8. An improved process as claimed in claim 1-7, wherein a polymeric layer is provided over the optional layer of reinforcing material.
9. A Glass - polymer hybrid multi-layer laminates having enhanced failure resistance made by the process as claimed in claims 1-8.
10. An improved process for the manufacture of glass - polymer hybrid multi-layer
laminates having enhanced failure resistance, substantially as herein described with
reference to the examples.

Documents:

467-DEL-2003-Abstract-(07-10-2010).pdf

467-del-2003-abstract.pdf

467-DEL-2003-Claims-(07-10-2010).pdf

467-del-2003-claims.pdf

467-DEL-2003-Correspondence-Others-(07-10-2010).pdf

467-del-2003-correspondence-others.pdf

467-del-2003-correspondence-po.pdf

467-DEL-2003-Description (Complete)-(07-10-2010).pdf

467-del-2003-description (complete).pdf

467-del-2003-form-1.pdf

467-del-2003-form-18.pdf

467-del-2003-form-2.pdf

467-DEL-2003-Form-3-(07-10-2010).pdf

467-del-2003-form-3.pdf

476-DEL-2003-Claims-(03-09-2008).pdf

476-DEL-2003-Correspondence-Others-(03-09-2008).pdf

476-DEL-2003-Petition-137-(03-09-2008).pdf

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Patent Number

243685

Indian Patent Application Number

467/DEL/2003

PG Journal Number

45/2010

Publication Date

05-Nov-2010

Grant Date

29-Oct-2010

Date of Filing

27-Mar-2003

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110 001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	ANOOP KUMAR MUKHOPADHYAY	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, KOLKATA 700 032, INDIA.
2	ANSHUMAN SEAL	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, KOLKATA 700 032, INDIA.
3	SRIKANTA DALUI	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, KOLKATA 700 032, INDIA.
4	KALYAN KUMAR PHANI	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, KOLKATA 700 032, INDIA.

PCT International Classification Number

B32B 7/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA