Title of Invention	A PROCESS FOR THE MANUFACTURE OF GLASS-POLYMER HYBRID MULTILAYER LAMINATES WITH IMPROVED FAILURE RESISTANCE AND GLASS-POLYMER HYBRID MULTILAYER LAMINATES MADE THEREBY
Abstract	A process for the manufacture of glass-polymer hybrid multilayer laminates with improved failure resistance and Glass - polymer hybrid multilayer laminates made thereby: The present invention provides a process for the manufacture of glass-polymer hybrid multilayer laminates with improved failure resistance characterized in that the hybrid multilayer glass-polymer laminates manufactured under a low uniaxial pressure in the range of 2-10 KPa at room temperature ( 25 °C ) to get improved characteristics . This hybrid laminate is useful as structural material for load bearing engineering applications.

Title of Invention

A PROCESS FOR THE MANUFACTURE OF GLASS-POLYMER HYBRID MULTILAYER LAMINATES WITH IMPROVED FAILURE RESISTANCE AND GLASS-POLYMER HYBRID MULTILAYER LAMINATES MADE THEREBY

Abstract

A process for the manufacture of glass-polymer hybrid multilayer laminates with improved failure resistance and Glass - polymer hybrid multilayer laminates made thereby: The present invention provides a process for the manufacture of glass-polymer hybrid multilayer laminates with improved failure resistance characterized in that the hybrid multilayer glass-polymer laminates manufactured under a low uniaxial pressure in the range of 2-10 KPa at room temperature ( 25 °C ) to get improved characteristics . This hybrid laminate is useful as structural material for load bearing engineering applications.

Full Text	The present invention relates to a process for the manufacture of glass-polymer hybrid multilayer laminates with improved failure resistance and Glass - polymer hybrid multilayer laminates made thereby: The main usage of this hybrid laminate 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 C.A. Folsom, F. W. Zok and F. F. lange, Journal of the American Ceramic Society, vol. 77, no.8, pp.2081-2087, 1994, wherein either indented thick glass slides (25 by 10 by 4mm) or unindented thin glass beams (75 by 38 byO.l5mm) were used as the matrix material in between alternate interfacial layers of a reinforcing polymer (ie. poly vinyl 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 had only 0.01 volume fraction of second phase and was needed, for the purpose of hot pressing, to be sealed in a Kapton envelop under high vacuum condition, thus making the process complicated. In the next stage, the entire assembly inside the Kapton envelop was hot pressed for three minutes under high vacuum at a high temperature of 175°C under a high uniaxial pressure of 350 KPa, thus making the process costlier. In addition, the very hot 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 brittle like fashion. Further, no assessment of the failure resistance of the glass-polymer multilayer composites fabricated by vacuum hot pressing was done. Thus, the major drawbacks of the hitherto known process are that it is complicated, costlier and the fabrication technique gives rise to strong interfacial bonding. The main object of the present invention is to provide a process for the manufacture of glass-polymer hybrid multilayer laminates having improved failure resistance which obviates the drawbacks as mentioned above. Another object of the present invention is to make the process for the manufacture of glass-polymer hybrid multilayer laminates simpler. Still another object of the present invention is to make the process for the manufacture of glass-polymer hybrid multilayer laminates cost effective. Yet another object of the present invention is to provide a means to tailor the manufacture procedure of the glas-polymer hybrid multilayer 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. Another object is to provide a glass-polymer hybrid multilayer laminates having improved failure resistance. In the process of the present invention, an innovative design philosophy has been adopted to obtain failure resistant glass polymer hybrid multilayer laminates. The clue to obtaining improvement was found to be linked to the achievement of controlled interfacial debonding leading to the growth of delamination cracks. The architecture of the multilayer composite involved alternate placement of a plurality of brittle and strong layers with a weak interface between the two. Low pressure lamination technique was exploited to develop the weak interface. This makes the process not only simpler but also cost effective. It has been shown further that depending on the type of reinforcement and the number of reinforcing layers, the failure resistance of the glass polymer hybrid multilayer composites can be enhanced to a value of as high as about 270 J/m2 in comparison to a low value of about 5 J/m2 obtained for the brittle glass matrix. Similarly, on the lower side value as small as about 20 J/m" could also be obtained for the failure resistance of the glass polymer hybrid multilayer composites, depending on 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 multilayer composites to suit a particular end application. The main usage of this hybrid composite 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. Accordingly, the present invention provides a process for the manufacture of glass-polymer hybrid multilayer laminates with improved failure resistance characterized in that the hybrid multilayer glass-polymer laminates manufactured under a low uniaxial pressure in the range of 2-10 KPa at room temperature ( 25 °C ) to get improved characteristics as herein described, the said process comprises the steps of washing thin glass sheets with detergent solution followed by water for a period in the range of 10 - 20 mins., rinsing the washed glass sheets with acetone for a period in the range of 5 - 15 mins., drying the rinsed glass sheets for a period in the range of 10 - 20 hrs at a temperature in the range of 80 - 120°C in air, keeping the dried glass sheets in a desiccator of a period in the range of 12 - 36 hrs. at room temperature, applying by conventional methods a layer of polymer such as herein described of thickness in the range of 38 - 320µm on one side of the glass sheets, making a stack of plurality of alternate glass and polymer layer followed by laminating the stack so obtained under a low 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 may be such as unannealed/annealed soda lime silica glass, borosilicate glass or aluminosilicate glass. In another embodiment of the present invention the thickness of the glass sheets used may be in the range of 0.3 - 1.0 mm. In yet another embodiment of the present invention the polymer used may be such as epoxy resin, poly vinyl butyral resin. In still another embodiment of the present invention interfacial layers of woven e-glass fabric or rovings may be provided along with polymeric layers. Accordingly, the present invention provides glass-polymer hybrid multilayer laminates made by the process of the present invention. 1. Annealed/unannealed glass sheets of thickness in the range of 0.3-1.0 mm are washed with detergent solution followed by water for 10-20 mins. 2. Washed glass sheets are rinsed with acetone for 5-15 minutes. 3. Rinsed glass sheets are dried for 10-20 hrs at 80-120°C in air. 4. Dried glass sheets are kept in a desiccator for 12-36 hrs. at room temperature. 5. Polymeric layer of thickness 38-320 urn thickness is applied by conventional methods on one side of the glass sheets and a stack of plurality of alternate glass and polymer layer is made. Optionally, an additional layer of woven e-glass fabric or roving is provided. 6. 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 clue to improved failure resistance of the glass polymer hybrid multilayer laminates lies in the achievement of controlled debonding at the interface. The present glass polymer hybrid multilayer laminates are provided with an alternate brittle-strong architecture having a deliberately introduced weak interfacial bonding between the brittle layer and the strong layer. The weak interfacial bonding is a consequence of the low pressure lamination technique applied at room temperature. Because the interfacial bonding is deliberately kept weak, as the brittle glass layer fails, the interfacial 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 multilayer 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 behaviour in the glass polymer hybrid multilayer laminates, the brittle glass matrix shows a characteristic fast fracture behaviour and hence a much lower value of failure energy. In the prior art indented thick glass slides or unindented thin glass beams were used as the matrix material in between alternate interfacial layers of a reinforcing polymer (ie. poly vinyl butyral, a thermoplastic resin) to fabricate the glass-polymer multilayer structure. The stack of the plurality of alternate glass and polymer layers needed, for the purpose of hot pressing, to be sealed in a Kapton envelop under high vacuum condition, thus making the process complicated. In the next stage, the entire assembly inside the Kapton envelop was hot pressed for three minutes under high vacuum at a high temperature of 175°C under a high uniaxial pressure of 350 KPa, thus making the process costlier. In addition, the very hot pressing technique used for the fabrication technique gave rise to more of strong bonding between the layers. Further, as a result of the high hot pressing temperature and pressure applied, the amount of the second phase reduced to a negligible 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 low pressure lamination of a plurality of alternate glass and a polymeric layer at room temperature. This inventive step of lamination at low pressure and room temperature caused a weak interfacial bonding between the plurality of glass and polymer layers. This weak interfacial bonding promoted controlled debonding when the glass-polymer hybrid multilayer laminate was subjected to stress. This controlled debonding led to a stepped load deformation behaviour, thus providing improved resistance to failure. The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention. EXAMPLE-1 To fabricate glass polymer hybrid multilayer laminates, ten number of thin circular glass disks was obtained commercially. The glass was a soda lime silica glass. 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 the average thickness was 0.3 mm. The as received thin circular glass discs were washed with detergent solution and flowing, doubly distilled water for a period of 20 minutes. 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 100°C. Finally, the glass disks were placed in a desiccator for 12 hrs prior to application of the epoxy polymeric layer by a hand lay-up technique. Thus, a plurality of stack of alternate glass disk and polymeric layer was developed with only one 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 value of the laminate was 2.44 gm/cc. The polymer layer had a thickness of 111 micron. Finally, the displacement to failure and 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 displacement at failure was 1.19 mm and the failure energy was 45.60 J/m2 as compared to the low failure energy of 5.03 J/m2 obtained for the thin matrix glass disks. EXAMPLE-2 To fabricate glass polymer hybrid multilayer laminates, twenty number of thin circular glass disks was obtained 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 the average thickness was 0.3 mm. The as received thin circular 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 5 minutes prior to putting in an air oven. The time of drying was 20 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. Thus, a stack of alternate glass disk and polymeric layer was developed with only 3 interfacial epoxy layer 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 4 KPa applied at room temperature (30°C) for a period of 15 hrs. The average density value of the laminate was 2.41 gm/cc. The polymer layer had a thickness of 80 micron. Finally, the displacement to failure and 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 displacement at failure was 1.67 mm and the failure energy was 269.82 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 multilayer laminates, twentyfive number of thin circular glass disks was obtained 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 the average thickness was 0.3 mm. The as received thin circular glass discs were washed with detergent solution 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 10 hrs. at 80°C. Finally, the glass disks were placed in a desiccator for 36 hrs prior to application of the epoxy polymeric layer by a spraying technique. Thus, a stack of alternate glass disk and polymeric layer was developed with four interfacial epoxy layer kept between the glass disks. To further reinforce the epoxy, in each of the four interfacial layers two dimensional, woven E-glass fabric of area density 242 gm/m2 was used after cutting the fabric to a diameter of 17mm. 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 4 KPa applied at room temperature (33°C) for a period of 15 hrs. The average density value of the laminate was 2.06 gm/cc. The polymeric layer had a thickness of 320 micron. Finally, the displacement to failure and 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 displacement at failure was 0.46 mm and the failure energy was 193.90 J/m2 as compared to the low failure energy of 5.03 J/m2 obtained for the thin matrix glass disks. EXAMPLE-4 To fabricate glass polymer hybrid multilayer laminates, ten number of thin circular glass disks was obtained 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 the average thickness was 0.3 mm. The as received thin circular glass discs were washed with detergent solution 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 26 hrs prior to application of the epoxy polymeric layer by a paint brush. Thus, a stack of alternate glass disk and polymeric layer was developed with one interfacial epoxy layer kept between the glass disks. To further reinforce the epoxy, in the interfacial layer E-glass roving having a tex of 1200 was used. The bunch of E-glass rovings was cut to sizes ranging from 7 mm to 16 mm and placed parallel to each other in a fashion as to be oriented perpendicular to one diameter of the circular glass disks. The pieces of reinforcing E-glass rovings were placed on the circular glass disk covered already with the reinforcing epoxy layer and then from the top the other layer of glass disk was placed carefully. The lamination of this stack of plurality 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 (33°C) for a period of 15 hrs. The average density value of the laminate was 2.08 gm/cc. The polymeric layer had a thickness of 100 micron. Finally, the displacement to failure and 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. The failure displacement of the laminate was 0.74 mm and the failure energy was 59.17 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 multilayer laminates, twentyfive number of thin circular glass disks was obtained 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 the average thickness was 0.3 mm. The as received thin circular glass discs were washed with detergent solution 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 20 hrs. at 120°C. Finally, the glass disks were placed in a desiccator for 36 hrs prior to application of the epoxy polymeric layer by a paint brush. Thus, a plurality of stack of alternate glass disk and polymeric layer was developed with four interfacial epoxy layer kept between the glass disks. To further reinforce the epoxy, in the interfacial layer E-glass roving having a tex of 1200 was used. The bunch of E-glass rovings was cut to sizes ranging from 7 mm to 16 mm and placed parallel to each other in a fashion as to be oriented perpendicular to one diameter of the circular glass disks. The pieces of reinforcing E-glass rovings were placed on the circular glass disk covered already with the reinforcing epoxy layer and then from the top the other layer of glass disk was placed carefully. The lamination of this stack of plurality 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 (33°C) for a period of 15 hrs. The average density value of the composite was 2.17 gm/cc. The polymeric layer had a thickness of 90 micron. Finally, the displacement to failure and 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. The failure displacement of the laminate was 0.56 mm and the failure energy was 145.17 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 multilayer laminates, fiftyfive number of thin square glass plates was obtained commercially. The glass was a soda lime silica glass. The length and breadth dimensions were measured by a callipers. Using the same instrument, the thickness of the disks was measured. The average dimension was 18 by 18 mm and the average thickness was 0.3 mm. The as received thin square glass plates were washed with detergent solution and flowing, doubly distilled water for a period of 20 minutes. The glass plates were finally rinsed with acetone for 15 minutes prior to putting in an air oven. The time of drying was 20 hrs. at 120°C. Finally, the glass plates were placed in a desiccator for 36 hrs prior to application of the epoxy polymeric layer by a spraying technique. Thus, a plurality of stack of alternate glass disk and polymeric layer was developed with ten interfacial epoxy layer kept between the glass disks. To further reinforce the epoxy, in each of the ten interfacial layers two dimensional woven E-glass fabric having a area density of 242 gm/m2 was used. The E-glass fabric was cut to a square of 17 by 17 mm size. The piece of reinforcing fabric was first soaked in the epoxy and then placed in 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 10 KPa applied at room temperature (30°C) for a period of 15 hrs. The average density value of the laminate was 1.80 gm/cc. The polymeric layer had a thickness of 290 micron. Finally, the displacement to failure and 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. The failure displacement of the laminate was 0.90 mm and the failure energy was 164.02 J/m2 as compared to the low failure energy of 5.02 J/m2 obtained for the thin matrix glass plates. EXAMPLE-7 To fabricate glass polymer hybrid multilayer laminates, fiftyfive number of thin square glass plates was obtained commercially. The glass was a borosilicate glass. The length and breadth dimensions were measured by a callipers. Using the same instrument, the thickness of the disks was measured. The average dimension was 18 by 18 mm and the average thickness was 0.3 mm. The as received thin square glass plates were washed with detergent solution and flowing, doubly distilled water for a period of 20 minutes to avoid surface contamination. The glass plates were finally rinsed with acetone for 15 minutes prior to putting in an air oven. The time of drying was 20 hrs. at 120°C. Finally, the glass plates were placed in a desiccator for 36 hrs prior to application of the epoxy polymeric layer by a hand lay-up technique. Thus, a plurality of stack of alternate glass disk and polymeric layer was developed with ten interfacial epoxy layer kept between the glass disks. To further reinforce the epoxy, in each of the ten interfacial layers two dimensional woven E-glass fabric having a area density of 242 gm/m2 was used. The E-glass fabric was cut to a square of 17 by 17 mm size. The piece of reinforcing fabric was first soaked in the epoxy and then placed in 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 10 KPa applied at room temperature (30°C) for a period of 15 hrs. The average density value of the laminate was 1.90 gm/cc. The polymeric layer had a thickness of 289 micron. Finally, the displacement to failure and 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. The failure displacement was 0.80 mm and the failure energy was 151.04 J/m2 as compared to the low failure energy of 4.29 J/m2 obtained for the thin matrix glass plates. EXAMPLE-8 To fabricate glass polymer hybrid multilayer laminates, fiftyfive number of thin square glass plates was obtained commercially. The glass was a aluminosilicate glass. The length and breadth dimensions were measured by a callipers. Using the same instrument, the thickness of the disks was measured. The average dimension was 18 by 18 mm and the average thickness was 0.3 mm. The as received thin square glass plates were washed with detergent solution and flowing, doubly distilled water for a period of 10 minutes to avoid surface contamination. The glass plates were finally rinsed with acetone for 15 minutes prior to putting in an air oven. The time of drying was 15 hrs. at 120°C. Finally, the glass plates were placed in a desiccator for 24 hrs prior to application of the epoxy polymeric layer by a paint brush. Thus, a plurality of stack of alternate glass disk and polymeric layer was developed with ten interfacial epoxy layer kept between the glass disks. To further reinforce the epoxy, in each of the ten interfacial layers two dimensional woven E-glass fabric having a area density of 242 gm/m2 was used. The E-glass fabric was cut to a square of 17 by 17 mm size. The piece of reinforcing fabric was first soaked in the epoxy and then placed in 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 10 KPa applied at room temperature (30°C) for a period of 15 hrs. The average density of the laminate was 1.78 gm/cc. The polymeric layer had a thickness of 297 micron. Finally, the displacement to failure and 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. The failure displacement of the laminate was 0.68 mm and the failure energy was 135.09 J/m2 as compared to the low failure energy of 3.19 J/m2 obtained for the thin matrix glass plates. EXAMPLE-9 To fabricate glass polymer hybrid multilayer laminates, ten number of thin glass slides was obtained commercially. The glass was a soda lime silica glass. The dimensions were measured by a callipers. Using the same instrument, the thickness of the slides was measured. The average dimension was 75 by 25 mm and the average thickness was 1 mm. The annealing schedule followed for the glass slides was as follows : 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 finally cooling from 300°C, @ 20°C/hr, to room temperature. The annealed thin slides were washed with detergent solution and flowing, doubly distilled water for a period of 20 minutes. The glass slides were finally 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 disks were placed in a desiccator for 12hrs prior to application of the epoxy polymeric layer by a spraying technique. Thus, a plurality of stack of alternate glass slide and polymeric layer was developed with only one 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 value was 2.38 gm/cc. The polymeric layer thickness was 68 micron. Finally, the displacement to failure and failure resistance was measured for these glass-polymer hybrid multilayer laminates in a universal testing machine and compared to that of the matrix glass slide. The failure displacement of the laminate was 0.17 mm and the failure energy was 9.88 J/m2 as compared to the low failure energy of 5.05 J/m2 obtained for the thin matrix glass slides. EXAMPLE-10 To fabricate glass polymer hybrid multilayer laminates, ten number of thin glass slides was obtained commercially. The glass was a soda lime silica glass. The dimensions were measured by a callipers. Using the same instrument, the thickness of the slides was measured. The average dimension was 75 by 25 mm and the average thickness was 1 mm. The annealing schedule followed for the glass slides was as follows : 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 finally cooling from 300°C, @ 20°C/hr. to room temperature. The annealed thin slides were washed with detergent solution and flowing, doubly distilled water for a period of 20 minutes. The glass slides were finally 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 slides were placed in a desiccator for 12hrs prior to application of the poly vinyl butyral polymeric layer by a paint brush. Thus, a plurality of stack of alternate glass slide and polymeric layer was developed with only one 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 2.42 gm/cc. The polymeric layer had a thickness of 38 micron. Finally, the displacement to failure and failure resistance was measured for these glass-polymer hybrid multilayer laminates in a universal and compared to that of the matrix glass disk. The failure displacement of the laminate was 0.19 mm and the failure energy was 12.15 J/m2 as compared to the low failure energy of 5.05 J/m2 obtained for the thin matrix glass slides. In the present invention there is provided a process for the fabrication of glass-polymer hybrid multilayer laminates having the novelty of improved resistance to failure. This has been achieved by the non-obvious inventive step of providing lamination of a plurality of alternate glass and a polymeric layer at low pressure at room temperature. This inventive step of lamination at low pressure and room temperature results in a weak interfacial bonding between the plurality of glass and polymer layers. This weak interfacial bonding brings about controlled debonding when the glass-polymer hybrid multilayer laminate is subjected to stress. This controlled debonding results in stepped load deformation behaviour, thus providing improved resistance to failure. The main advantages of the present process are : 1. It provides a means for the fabrication of glass-polymer hybrid multilayer laminates with improved failure resistance. 2. Another advantage of the present invention is that it has made the process for the fabrication of glass-polymer hybrid multilayer laminates much simpler than the earlier process. 3. Still another advantage of the present invention is that it has made the process for the fabrication of glass-polymer hybrid multilayer laminates more cost effective than the earlier process. 4. Yet another advantage of the present invention is that it provides means to tailor the fabrication procedure of the glass-polymer hybrid multilayer laminates in terms of the choice of polymeric layer, 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. A process for the manufacture of glass-polymer hybrid multilayer laminates with improved failure resistance characterized in that the hybrid multilayer glass-polymer laminates manufactured under a low uniaxial pressure in the range of 2-10 KPa at room temperature ( 25 °C ) to get improved characteristics as herein described, the said process comprises the steps of washing thin glass sheets with detergent solution followed by water for a period in the range of 10 - 20 mins., rinsing the washed glass sheets with acetone for a period in the range of 5 - 15 mins., drying the rinsed glass sheets for a period in the range of 10 - 2.0 hrs at a temperature in the range of 80 - 120°C in air, keeping the dried glass sheets in a desiccator of a period in the range of 12 - 36 hrs. at room temperature, applying by conventional methods a layer of polymer such as herein described of thickness in the range of 38 - 320µm on one side of the glass sheets, making a stack of plurality of alternate glass and polymer layer followed by laminating the stack so obtained under a low uniaxial pressure in the range of 2 - 10 KPa at room temperature for a period in the range of 10 - 15 hrs. 2. A 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. A process as claimed in claim 1-2 wherein the thickness of the glass sheets used is in the range of 0.3 - 1.0 mm. 4. A process as claimed in claim 1 , wherein the polymer used is selected from epoxy resin, poly vinyl butyral resin. 5. A glass-polymer hybrid multiplayer laminates made by the process as claimed in claims 1-5. 6. A process for the manufacture of glass-polymer hybrid multilayer laminates with improved failure resistance substantially as herein described with reference to the examples accompanying this specification. 7. Glass - polymer hybrid multilayer laminates substantially as herein described with reference to the examples.

Full Text

The present invention relates to a process for the manufacture of glass-polymer hybrid multilayer laminates with improved failure resistance and Glass - polymer hybrid multilayer laminates made thereby:
The main usage of this hybrid laminate 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 C.A. Folsom, F. W. Zok and F. F. lange, Journal of the American Ceramic Society, vol. 77, no.8, pp.2081-2087, 1994, wherein either indented thick glass slides (25 by 10 by 4mm) or unindented thin glass beams (75 by 38 byO.l5mm) were used as the matrix material in between alternate interfacial layers of a reinforcing polymer (ie. poly vinyl 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 had only 0.01 volume fraction of second phase and was needed, for the purpose of hot pressing, to be sealed in a Kapton envelop under high vacuum condition, thus making the process complicated. In the next stage, the entire assembly inside the Kapton envelop was hot pressed for three minutes under high vacuum at a high temperature of 175°C under a high uniaxial pressure of 350 KPa, thus making the process costlier. In addition, the very hot 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 brittle like fashion. Further, no assessment of the

failure resistance of the glass-polymer multilayer composites fabricated by vacuum hot pressing was done. Thus, the major drawbacks of the hitherto known process are that it is complicated, costlier and the fabrication technique gives rise to strong interfacial bonding.
The main object of the present invention is to provide a process for the manufacture of glass-polymer hybrid multilayer laminates having improved failure resistance which obviates the drawbacks as mentioned above.
Another object of the present invention is to make the process for the manufacture of glass-polymer hybrid multilayer laminates simpler.
Still another object of the present invention is to make the process for the manufacture of glass-polymer hybrid multilayer laminates cost effective.
Yet another object of the present invention is to provide a means to tailor the manufacture procedure of the glas-polymer hybrid multilayer 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.
Another object is to provide a glass-polymer hybrid multilayer laminates having improved failure resistance.
In the process of the present invention, an innovative design philosophy has been adopted to obtain failure resistant glass polymer hybrid multilayer laminates. The clue to obtaining improvement was found to be linked to the achievement of controlled interfacial debonding leading to the growth of delamination cracks. The architecture of the multilayer composite involved alternate placement of a plurality of brittle and strong layers with a weak interface between the two. Low pressure lamination technique was exploited to develop the weak interface. This makes the process not only simpler but also cost effective. It has been shown further that depending on the type of reinforcement and the number of reinforcing layers, the failure resistance of the glass polymer hybrid multilayer composites can be enhanced to a value of as high as about 270 J/m2 in comparison to a low value of about 5 J/m2 obtained for the brittle glass matrix. Similarly, on the lower side value as small as about 20 J/m" could also be obtained for the failure resistance of the glass polymer hybrid multilayer composites, depending on 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 multilayer composites to suit a particular end application. The main usage of this hybrid composite 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.
Accordingly, the present invention provides a process for the manufacture of glass-polymer hybrid multilayer laminates with improved failure resistance characterized in that the hybrid multilayer glass-polymer laminates manufactured under a low uniaxial pressure in the range of 2-10 KPa at room temperature ( 25 °C ) to get improved characteristics as herein described, the said process comprises the steps of washing thin glass sheets with detergent solution followed by water for a period in the range of 10 - 20 mins., rinsing the washed glass sheets with acetone for a period in the range of 5 - 15 mins., drying the rinsed glass sheets for a period in the range of 10 - 20 hrs at a temperature in the range of 80 - 120°C in air, keeping the dried glass sheets in a desiccator of a period in the range of 12 - 36 hrs. at room temperature, applying by conventional methods a layer of polymer such as herein described of thickness in the range of 38 - 320µm on one side of the glass sheets, making a stack of plurality of alternate glass and polymer layer followed by laminating the stack so obtained under a low 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 may be such as unannealed/annealed soda lime silica glass, borosilicate glass or aluminosilicate glass.
In another embodiment of the present invention the thickness of the glass sheets used may be in the range of 0.3 - 1.0 mm.
In yet another embodiment of the present invention the polymer used may be such as epoxy resin, poly vinyl butyral resin.
In still another embodiment of the present invention interfacial layers of woven e-glass fabric or rovings may be provided along with polymeric layers. Accordingly, the present invention provides glass-polymer hybrid multilayer laminates made by the process of the present invention.
1. Annealed/unannealed glass sheets of thickness in the range of 0.3-1.0 mm are
washed with detergent solution followed by water for 10-20 mins.
2. Washed glass sheets are rinsed with acetone for 5-15 minutes.
3. Rinsed glass sheets are dried for 10-20 hrs at 80-120°C in air.
4. Dried glass sheets are kept in a desiccator for 12-36 hrs. at room temperature.
5. Polymeric layer of thickness 38-320 urn thickness is applied by conventional
methods on one side of the glass sheets and a stack of plurality of alternate glass
and polymer layer is made. Optionally, an additional layer of woven e-glass
fabric or roving is provided.
6. 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 clue to improved failure resistance of the glass polymer hybrid multilayer laminates lies in the achievement of controlled debonding at the interface. The present glass polymer hybrid multilayer laminates are provided with an alternate brittle-strong architecture having a deliberately introduced weak interfacial bonding between the brittle layer and the strong layer. The weak interfacial bonding is a consequence of the low pressure lamination technique applied at room temperature. Because the interfacial bonding is deliberately kept weak, as the brittle glass layer fails, the interfacial 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 multilayer 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 behaviour in the glass polymer hybrid multilayer laminates, the brittle glass matrix shows a characteristic fast fracture behaviour and hence a much lower value of failure energy. In the prior art indented thick glass slides or unindented thin glass beams were used as the matrix material in between alternate interfacial layers of a reinforcing polymer (ie. poly vinyl butyral, a thermoplastic resin) to fabricate the glass-polymer multilayer structure. The stack of the plurality of alternate glass and polymer layers needed, for the purpose of hot pressing, to be sealed in a Kapton envelop under high vacuum condition, thus making the process complicated. In the next stage, the entire assembly inside the Kapton envelop was hot pressed for three minutes under high vacuum at a high temperature of 175°C under a high uniaxial pressure of 350 KPa, thus making the process costlier. In addition, the very hot pressing technique used for the fabrication technique gave rise to more of strong bonding between the layers. Further, as a result of the high hot pressing temperature and pressure applied, the amount of the second phase reduced to a negligible 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 low pressure lamination of a plurality of alternate glass and a polymeric layer at room temperature. This inventive step of lamination at low pressure and room temperature caused a weak interfacial bonding between the plurality of glass and polymer layers. This weak interfacial bonding promoted controlled debonding when the glass-polymer hybrid multilayer laminate was subjected to stress. This controlled debonding led to a stepped load deformation behaviour, thus providing improved resistance to failure.
The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention.
EXAMPLE-1
To fabricate glass polymer hybrid multilayer laminates, ten number of thin circular glass disks was obtained commercially. The glass was a soda lime silica glass. 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 the average thickness was 0.3 mm. The as received thin circular glass discs were washed with detergent solution and flowing, doubly distilled water for a period of 20 minutes. 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 100°C. Finally, the glass disks were placed in a desiccator for 12 hrs prior to application of the epoxy polymeric layer by a hand lay-up technique. Thus, a plurality of stack of alternate glass disk and polymeric layer was developed with only one 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 value of the laminate was 2.44 gm/cc. The polymer layer had a thickness of 111 micron. Finally, the displacement to failure and 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 displacement at failure was 1.19 mm and the failure energy was 45.60 J/m2 as compared to the low failure energy of 5.03 J/m2 obtained for the thin matrix glass disks.
EXAMPLE-2
To fabricate glass polymer hybrid multilayer laminates, twenty number of thin circular glass disks was obtained 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 the average thickness was 0.3 mm. The as received thin circular 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 5 minutes prior to putting in an air oven. The time of drying was 20 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. Thus, a stack of alternate glass disk and polymeric layer was developed with only 3 interfacial epoxy layer 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 4 KPa applied at room temperature (30°C) for a period of 15 hrs. The average density value of the laminate was 2.41 gm/cc. The polymer layer had a thickness of 80 micron. Finally, the displacement to failure and 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 displacement at failure was 1.67 mm and the failure energy was 269.82 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 multilayer laminates, twentyfive number of thin circular glass disks was obtained 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 the average thickness was 0.3 mm. The as received thin circular glass discs were washed with detergent solution 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 10 hrs. at 80°C. Finally, the glass disks were placed in a desiccator for 36 hrs prior to application of the epoxy polymeric layer by a spraying technique. Thus, a stack of alternate glass disk and polymeric layer was developed with four interfacial epoxy layer kept between the glass disks. To further reinforce the epoxy, in each of the four interfacial layers two dimensional, woven E-glass fabric of area density 242 gm/m2 was
used after cutting the fabric to a diameter of 17mm. 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 4 KPa applied at room temperature (33°C) for a period of 15 hrs. The average density value of the laminate was 2.06 gm/cc. The polymeric layer had a thickness of 320 micron. Finally, the displacement to failure and 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 displacement at failure was 0.46 mm and the failure energy was 193.90 J/m2 as compared to the low failure energy of 5.03 J/m2 obtained for the thin matrix glass disks.
EXAMPLE-4
To fabricate glass polymer hybrid multilayer laminates, ten number of thin circular glass disks was obtained 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 the average thickness was 0.3 mm. The as received thin circular glass discs were washed with detergent solution 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 26 hrs prior to application of the epoxy polymeric layer by a paint brush. Thus, a stack of alternate glass disk and polymeric layer was developed with one interfacial epoxy layer kept between the glass disks. To further reinforce the epoxy, in the interfacial layer E-glass roving having a tex
of 1200 was used. The bunch of E-glass rovings was cut to sizes ranging from 7 mm to 16 mm and placed parallel to each other in a fashion as to be oriented perpendicular to one diameter of the circular glass disks. The pieces of reinforcing E-glass rovings were placed on the circular glass disk covered already with the reinforcing epoxy layer and then from the top the other layer of glass disk was placed carefully. The lamination of this stack of plurality 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 (33°C) for a period of 15 hrs. The average density value of the laminate was 2.08 gm/cc. The polymeric layer had a thickness of 100 micron. Finally, the displacement to failure and 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. The failure displacement of the laminate was 0.74 mm and the failure energy was 59.17 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 multilayer laminates, twentyfive number of thin circular glass disks was obtained 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 the average thickness was 0.3 mm. The as received thin circular glass discs were washed with detergent solution 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 20 hrs. at 120°C. Finally, the glass disks were placed in a desiccator for 36 hrs prior to application of the epoxy polymeric layer by a paint brush. Thus, a plurality of stack of alternate glass disk and polymeric layer was developed with four interfacial epoxy layer kept between the glass disks. To further reinforce the epoxy, in the interfacial layer E-glass roving having a tex of 1200 was used. The bunch of E-glass rovings was cut to sizes ranging from 7 mm to 16 mm and placed parallel to each other in a fashion as to be oriented perpendicular to one diameter of the circular glass disks. The pieces of reinforcing E-glass rovings were placed on the circular glass disk covered already with the reinforcing epoxy layer and then from the top the other layer of glass disk was placed carefully. The lamination of this stack of plurality 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 (33°C) for a period of 15 hrs. The average density value of the composite was 2.17 gm/cc. The polymeric layer had a thickness of 90 micron. Finally, the displacement to failure and 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. The failure displacement of the laminate was 0.56 mm and the failure energy was 145.17 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 multilayer laminates, fiftyfive number of thin square glass plates was obtained commercially. The glass was a soda lime silica glass. The length and breadth dimensions were measured by a callipers. Using the same instrument, the thickness of the disks was measured. The average dimension was 18 by 18 mm and the average thickness was 0.3 mm. The as received thin square glass plates were washed with detergent solution and flowing, doubly distilled water for a period of 20 minutes. The glass plates were finally rinsed with acetone for 15 minutes prior to putting in an air oven. The time of drying was 20 hrs. at 120°C. Finally, the glass plates were placed in a desiccator for 36 hrs prior to application of the epoxy polymeric layer by a spraying technique. Thus, a plurality of stack of alternate glass disk and polymeric layer was developed with ten interfacial epoxy layer kept between the glass disks. To further reinforce the epoxy, in each of the ten interfacial layers two dimensional woven E-glass fabric having a area density of 242 gm/m2 was used. The E-glass fabric was cut to a square of 17 by 17 mm size. The piece of reinforcing fabric was first soaked in the epoxy and then placed in 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 10 KPa applied at room temperature (30°C) for a period of 15 hrs. The average density value of the laminate was 1.80 gm/cc. The polymeric layer had a thickness of 290 micron. Finally, the displacement to failure and 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. The failure displacement of the laminate was 0.90 mm and the failure energy was 164.02 J/m2 as compared to the low failure energy of 5.02 J/m2 obtained for the thin matrix glass plates.
EXAMPLE-7
To fabricate glass polymer hybrid multilayer laminates, fiftyfive number of thin square glass plates was obtained commercially. The glass was a borosilicate glass. The length and breadth dimensions were measured by a callipers. Using the same instrument, the thickness of the disks was measured. The average dimension was 18 by 18 mm and the average thickness was 0.3 mm. The as received thin square glass plates were washed with detergent solution and flowing, doubly distilled water for a period of 20 minutes to avoid surface contamination. The glass plates were finally rinsed with acetone for 15 minutes prior to putting in an air oven. The time of drying was 20 hrs. at 120°C. Finally, the glass plates were placed in a desiccator for 36 hrs prior to application of the epoxy polymeric layer by a hand lay-up technique. Thus, a plurality of stack of alternate glass disk and polymeric layer was developed with ten interfacial epoxy layer kept between the glass disks. To further reinforce the epoxy, in each of the ten interfacial layers two dimensional woven E-glass fabric having a area density of 242 gm/m2 was used. The E-glass fabric was cut to a square of 17 by 17 mm size. The piece of reinforcing fabric was first soaked in the epoxy and then placed in 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 10 KPa applied at room temperature
(30°C) for a period of 15 hrs. The average density value of the laminate was 1.90 gm/cc. The polymeric layer had a thickness of 289 micron. Finally, the displacement to failure and 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. The failure displacement was 0.80 mm and the failure energy was 151.04 J/m2 as compared to the low failure energy of 4.29 J/m2 obtained for the thin matrix glass plates.
EXAMPLE-8
To fabricate glass polymer hybrid multilayer laminates, fiftyfive number of thin square glass plates was obtained commercially. The glass was a aluminosilicate glass. The length and breadth dimensions were measured by a callipers. Using the same instrument, the thickness of the disks was measured. The average dimension was 18 by 18 mm and the average thickness was 0.3 mm. The as received thin square glass plates were washed with detergent solution and flowing, doubly distilled water for a period of 10 minutes to avoid surface contamination. The glass plates were finally rinsed with acetone for 15 minutes prior to putting in an air oven. The time of drying was 15 hrs. at 120°C. Finally, the glass plates were placed in a desiccator for 24 hrs prior to application of the epoxy polymeric layer by a paint brush. Thus, a plurality of stack of alternate glass disk and polymeric layer was developed with ten interfacial epoxy layer kept between the glass disks. To further reinforce the epoxy, in each of the ten interfacial layers two dimensional woven E-glass fabric having a area density of 242 gm/m2 was used. The E-glass fabric was cut to a square of 17 by 17 mm size. The piece of reinforcing fabric was first soaked in the epoxy and then placed in 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 10 KPa applied at room temperature (30°C) for a period of 15 hrs. The average density of the laminate was 1.78 gm/cc. The polymeric layer had a thickness of 297 micron. Finally, the displacement to failure and 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. The failure displacement of the laminate was 0.68 mm and the failure energy was 135.09 J/m2 as compared to the low failure energy of 3.19 J/m2 obtained for the thin matrix glass plates.
EXAMPLE-9
To fabricate glass polymer hybrid multilayer laminates, ten number of thin glass slides was obtained commercially. The glass was a soda lime silica glass. The dimensions were measured by a callipers. Using the same instrument, the thickness of the slides was measured. The average dimension was 75 by 25 mm and the average thickness was 1 mm. The annealing schedule followed for the glass slides was as follows : 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 finally cooling from 300°C, @ 20°C/hr, to room temperature. The annealed thin slides were washed with detergent solution and flowing, doubly distilled water for a period of 20 minutes. The glass slides were finally 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 disks were placed in a
desiccator for 12hrs prior to application of the epoxy polymeric layer by a spraying technique. Thus, a plurality of stack of alternate glass slide and polymeric layer was developed with only one 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 value was 2.38 gm/cc. The polymeric layer thickness was 68 micron. Finally, the displacement to failure and failure resistance was measured for these glass-polymer hybrid multilayer laminates in a universal testing machine and compared to that of the matrix glass slide. The failure displacement of the laminate was 0.17 mm and the failure energy was 9.88 J/m2 as compared to the low failure energy of 5.05 J/m2 obtained for the thin matrix glass slides.
EXAMPLE-10
To fabricate glass polymer hybrid multilayer laminates, ten number of thin glass slides was obtained commercially. The glass was a soda lime silica glass. The dimensions were measured by a callipers. Using the same instrument, the thickness of the slides was measured. The average dimension was 75 by 25 mm and the average thickness was 1 mm. The annealing schedule followed for the glass slides was as follows : 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 finally cooling from 300°C, @ 20°C/hr. to room temperature. The annealed thin slides were washed with detergent solution and flowing, doubly distilled water for a period of 20 minutes. The
glass slides were finally 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 slides were placed in a desiccator for 12hrs prior to application of the poly vinyl butyral polymeric layer by a paint brush. Thus, a plurality of stack of alternate glass slide and polymeric layer was developed with only one 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 2.42 gm/cc. The polymeric layer had a thickness of 38 micron. Finally, the displacement to failure and failure resistance was measured for these glass-polymer hybrid multilayer laminates in a universal and compared to that of the matrix glass disk. The failure displacement of the laminate was 0.19 mm and the failure energy was 12.15 J/m2 as compared to the low failure energy of 5.05 J/m2 obtained for the thin matrix glass slides.
In the present invention there is provided a process for the fabrication of glass-polymer hybrid multilayer laminates having the novelty of improved resistance to failure. This has been achieved by the non-obvious inventive step of providing lamination of a plurality of alternate glass and a polymeric layer at low pressure at room temperature. This inventive step of lamination at low pressure and room temperature results in a weak interfacial bonding between the plurality of glass and polymer layers. This weak interfacial bonding brings about controlled debonding when the glass-polymer hybrid multilayer laminate is subjected to stress. This controlled debonding results in stepped load deformation behaviour, thus providing improved resistance to failure.
The main advantages of the present process are :
1. It provides a means for the fabrication of glass-polymer hybrid multilayer laminates
with improved failure resistance.
2. Another advantage of the present invention is that it has made the process for the
fabrication of glass-polymer hybrid multilayer laminates much simpler than the earlier
process.
3. Still another advantage of the present invention is that it has made the process for the
fabrication of glass-polymer hybrid multilayer laminates more cost effective than the
earlier process.
4. Yet another advantage of the present invention is that it provides means to tailor the
fabrication procedure of the glass-polymer hybrid multilayer laminates in terms of the
choice of polymeric layer, 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. A process for the manufacture of glass-polymer hybrid multilayer laminates with improved failure resistance characterized in that the hybrid multilayer glass-polymer laminates manufactured under a low uniaxial pressure in the range of 2-10 KPa at room temperature ( 25 °C ) to get improved characteristics as herein described, the said process comprises the steps of washing thin glass sheets with detergent solution followed by water for a period in the range of 10 - 20 mins., rinsing the washed glass sheets with acetone for a period in the range of 5 - 15 mins., drying the rinsed glass sheets for a period in the range of 10 - 2.0 hrs at a temperature in the range of 80 - 120°C in air, keeping the dried glass sheets in a desiccator of a period in the range of 12 - 36 hrs. at room temperature, applying by conventional methods a layer of polymer such as herein described of thickness in the range of 38 - 320µm on one side of the glass sheets, making a stack of plurality of alternate glass and polymer layer followed by laminating the stack so obtained under a low uniaxial pressure in the range of 2 - 10 KPa at room temperature for a period in the range of 10 - 15 hrs.
2. A 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. A process as claimed in claim 1-2 wherein the thickness of the glass sheets
used is in the range of 0.3 - 1.0 mm.
4. A process as claimed in claim 1 , wherein the polymer used is selected from
epoxy resin, poly vinyl butyral resin.
5. A glass-polymer hybrid multiplayer laminates made by the process as claimed
in claims 1-5.
6. A process for the manufacture of glass-polymer hybrid multilayer laminates
with improved failure resistance substantially as herein described with
reference to the examples accompanying this specification.
7. Glass - polymer hybrid multilayer laminates substantially as herein described
with reference to the examples.

Documents:

51-del-2002-abstract.pdf

51-del-2002-claims.pdf

51-del-2002-correspondence-others.pdf

51-del-2002-correspondence-po.pdf

51-del-2002-description (complete).pdf

51-del-2002-form-1.pdf

51-del-2002-form-18.pdf

51-del-2002-form-2.pdf

51-del-2002-form-3.pdf

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Patent Number

232797

Indian Patent Application Number

51/DEL/2002

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

21-Mar-2009

Date of Filing

25-Jan-2002

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH,

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	ANOOP KUMAR MUKHOPADHYAY	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, KOLKATA 700032, INDIA.
2	SRIKANTA KUMAR DALUI	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, KOLKATA 700032, INDIA.
3	ANSHUMAN SEAL	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, KOLKATA 700032, INDIA.
4	KALYAN KUMAR PHANI	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, KOLKATA 700032, INDIA.
5	HIMADRI SEKHAR MAITI	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, KOLKATA 700032, INDIA.

PCT International Classification Number

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA