RELATED APPLICATION

[0001] This application claims the benefit of priority under 35 U.S.C. §119(e) to United States Appln. Ser. No. 62/168,089, filed May 29, 2015, the contents of which are

incorporated by reference.

BACKGROUND

[0002] Transparent structural materials are widely used in both military and commercial applications. In the military, protective armor materials that are transparent to visible light (380-750 nm wavelength range) are needed for many situations, such as soldier eye/face protection (e.g., face shields, goggles), windshields and windows, blast shields, and combat vehicle vision blocks. Transparent armor materials for commercial applications include face shields, security glass, armored cars, and other vehicles. Moreover, light transmitting safety glass is also widely used for windows, windshields, sunroofs, skylights, display cases, picture frames and similar applications. Recently, transparent cover glass with improved scratch and fracture resistance has been widely used for a variety of personal electronic devices, such as tablets and smartphones.

[0003] The most common transparent structural materials are based on glass laminates, which combine multiple layers of glass sandwiched with thin plastic adhesive interlayers such as polyvinyl butyral (PVB). Though there have been some technological advances in producing improved transparent composite materials, the majority of current design and fabrication strategies for protective transparent materials is primarily based on empirical and trial-and-error approaches. Therefore, developing new transparent armor materials is usually time consuming and costly.

[0004] One particular drawback of current glass laminate composites is their low damage tolerance and lack of multi-hit capability. The ability to view through these materials after an initial impact event is dramatically reduced because of the extensive crack propagation through the composite. SUMMARY OF INVENTION

[0005] In an aspect, a hybrid glass includes a first layer of glass; a second layer of glass; a first heterogeneous interlayer disposed in between the first layer of glass and the second layer of glass; wherein the first heterogeneous interlayer comprises at least a first and a second phase, wherein the first phase has a measured value of a property greater than that of the second phase, wherein the property is selected from a group consisting of Young's modulus, fracture strength, fracture toughness, storage modulus, loss modulus, elastic modulus, hardness and interfacial adhesion strength; wherein the first and second phases of the first heterogeneous interlayer form a point or area of contact with the first layer of glass and the second layer of glass; and wherein at least one of the first and second phases of the first heterogeneous interlayer forms an adhesive bond with the first layer of glass and the second layer of glass.

[0006] In some embodiments, the measured property of the first phase and the second phase of the first heterogeneous layer are measured using tensile testing, dynamic mechanical analysis, nanoindentation, dynamic nanoindentation, shore hardness test, Rockwell hardness test, Vickers hardness test, Brinell hardness test, or, microhardness test.

[0007] In some embodiments, one or more of the first glass layer, second glass layer and the first heterogeneous interlayer are transparent. In some embodiments, one or more of the first layer of glass, the second layer of glass and the first heterogeneous interlayer are index- matched.

[0008] In some embodiments, the first phase of the first heterogeneous interlayer comprises a first polymeric adhesive; wherein the first polymeric adhesive forms a discontinuous region in the interlayer. In some embodiments, the second phase of the first heterogeneous interlayer comprises a second polymeric adhesive; wherein the second polymeric adhesive forms a discontinuous region in the interlayer. In some embodiments, the first phase of the first heterogeneous interlayer comprises a first polymeric adhesive; wherein the first polymeric adhesive forms a continuous region in the interlayer. In some

embodiments, the second phase of the first heterogeneous interlayer comprises a second polymeric adhesive; wherein the second polymeric adhesive forms a continuous region in the interlayer. [0009] In some embodiments, the second phase of the first heterogeneous interlayer is air or a liquid.

[0010] In some embodiments, the discontinuous regions of the first phase and the second phase of the first heterogeneous interlayer form an interpenetrating network.

[0011] In some embodiments, the areas of contact of the first phase of the first heterogeneous interlayer with the first layer of glass or the second layer of glass forms a regular array. In some embodiments, the areas of contact of the first phase of the first heterogeneous interlayer with the first layer of glass or the second layer of glass forms an irregular array.

[0012] In some embodiments, the first heterogeneous interlayer is a phase separating polymer that has separated to form at least two phases.

[0013] In some embodiments, the surface of one or more of the first layer of glass and the second layer of glass are treated with an adhesion promoter to improve the adhesion with the first heterogeneous interlayer.

[0014] In some embodiments the hybrid glass further includes, a second heterogeneous interlayer disposed over the first layer of glass or the second layer of glass; and a third layer of glass disposed over, the second heterogeneous interlayer, wherein the second

heterogeneous interlayer comprises at least a third and a fourth phase, wherein the third phase has a measured value of a property greater than that of the fourth phase, wherein the property is selected from a group consisting of Young's modulus, fracture strength, fracture toughness, storage modulus, loss modulus, elastic modulus, hardness and interfacial adhesion strength; wherein the third phase and fourth phase of the second heterogeneous interlayer forms a point or area of contact with the first layer of glass or the second layer of glass, and the third layer of glass; and wherein at least one of the third phase and fourth phase of the second

heterogeneous interlayer forms an adhesive bond with the first layer of glass or the second layer of glass, and the third layer of glass.

[0015] In some embodiments, the measured property of the third phase and the fourth phase of the second heterogeneous layer are measured using tensile testing, dynamic mechanical analysis, nanoindentation, dynamic nanoindentation, shore hardness test, Rockwell hardness test, Vickers hardness test, Brinell hardness test, or, microhardness test.

[0016] In some embodiments, the first heterogeneous interlayer and the second heterogeneous interlayer are made of the same material.

[0017] In some embodiments, the first heterogeneous interlayer and the second heterogeneous interlayer are made of materials with different composition.

[0018] In some embodiments, wherein the fourth phase of the second heterogeneous interlayer is air or a liquid.

[0019] In some embodiments, wherein the discontinuous regions of the third phase and the fourth phase of second heterogeneous interlayer form an interpenetrating network.

[0020] In some embodiments, the areas of contact of the third phase of the second heterogeneous interlayer with the first layer of glass, second layer of glass or third layer of glass forms a regular array. In some embodiments, the areas of contact of the third phase of the second heterogeneous interlayer with the first layer of glass, second layer of glass or third layer of glass forms an irregular array.

[0021] In some embodiments, the second heterogeneous interlayer is a phase separating polymer that has separated to form at least two phases.

[0022] In some embodiments, wherein the surface of one or more of the first layer of glass, the second layer of glass, and the third layer of glass are treated with an adhesion promoter to improve the adhesion with the heterogeneous interlayer.

[0023] In an aspect, a method of manufacturing a hybrid glass includes, providing a first layer of glass; providing a second layer of glass; providing a first heterogeneous interlayer disposed in between the first layer of glass and the second layer of glass; wherein the first heterogeneous interlayer comprises at least a first and a second phase, wherein the first phase has a measured value of a property greater than that of the second phase, wherein the property is selected from a group consisting of Young's modulus, fracture strength, fracture toughness, storage modulus, loss modulus, elastic modulus, hardness and interfacial adhesion strength; applying the first layer of heterogeneous interlayer material on the first or second layer of glass; wherein the first and second phases of the first heterogeneous interlayer form a point of contact with the first and second layer of glass; and wherein at least one of the first and second phases of the first heterogeneous interlayer forms an adhesive bond with the first and second layer of glass.

[0024] In some embodiments, the measured property of the first phase and the second phase of the first heterogeneous layer are measured using tensile testing, dynamic mechanical analysis, nanoindentation, dynamic nanoindentation, shore hardness test, Rockwell hardness test, Vickers hardness test, Brinell hardness test, or, microhardness test.

[0025] In some embodiments, one or more of the first glass layer, second glass layer and the first interlayer are transparent. In some embodiments, one or more of the first layer of glass, the second layer of glass and the first heterogeneous interlayer are index-matched.

[0026] In some embodiments, the first phase of the first heterogeneous interlayer comprises a first polymeric adhesive; wherein the first polymeric adhesive forms a discontinuous region in the interlayer. In some embodiments, the second phase of the first heterogeneous interlayer comprises a second polymeric adhesive; wherein the second polymeric adhesive forms a discontinuous region in the interlayer . In some embodiments, the first phase of the first heterogeneous interlayer comprises a first polymeric adhesive; wherein the first polymeric adhesive forms a continuous region in the interlayer. In some

embodiments, the second phase of the first heterogeneous interlayer comprises a second polymeric adhesive; wherein the second polymeric adhesive forms a continuous region in the interlayer .

[0027] In some embodiments, the second phase of the first heterogeneous interlayer is air or a liquid.

[0028] In some embodiments, wherein the discontinuous regions of the first phase and the second phase of the transparent interlayer form an interpenetrating network.

[0029] In some embodiments, wherein the areas of contact of the first phase of the first heterogeneous interlayer with the first layer of glass or the second layer of glass forms a regular array. In some embodiments, wherein the areas of contact of the first phase of the first heterogeneous interlayer with the first layer of glass or the second layer of glass forms an irregular array.

[0030] In some embodiments, wherein the first heterogeneous interlayer is a phase separating polymer that has separated to form at least two phases.

[0031] In some embodiments, the surface of the first layer of glass and the second layer of glass is treated with an adhesion promoter to improve the adhesion with the heterogeneous interlayer.

[0032] In some embodiments, the method further includes; providing a second heterogeneous interlayer to be disposed over the first layer of glass or the second layer of glass; and providing a third layer of glass to be disposed over, the second heterogeneous interlayer, wherein the second heterogeneous interlayer comprises at least a third and a fourth phase, wherein the third phase has a measured value of a property greater than that of the fourth phase, wherein the property is selected from a group consisting of Young's modulus, fracture strength, fracture toughness, storage modulus, loss modulus, elastic modulus, hardness and interfacial adhesion strength; wherein the third and fourth phases of the second heterogeneous interlayer form a point of contact with the first or second, and third layer of glass; and wherein at least one of the third and fourth phases of the second heterogeneous interlayer form an adhesive bond with the first or second, and third layer of glass.

[0033] In some embodiments, the measured property of the third phase and the fourth phase of the second heterogeneous layer are measured using tensile testing, dynamic mechanical analysis, nanoindentation, dynamic nanoindentation, shore hardness test, Rockwell hardness test, Vickers hardness test, Brinell hardness test, or, microhardness test.

[0034] In some embodiments, wherein the first heterogeneous interlayer layer and the second heterogeneous interlayer are made of the same material.

[0035] In some embodiments, wherein the first heterogeneous interlayer layer and the second heterogeneous interlayer are made of materials with different composition.

[0036] In some embodiments, wherein the fourth phase of the second heterogeneous interlayer is air or a liquid. [0037] In some embodiments, wherein the discontinuous regions of the third and the fourth phases of second heterogeneous interlayer form an interpenetrating network.

[0038] In some embodiments, wherein the areas of contact of the third phase of the second heterogeneous interlayer with the first, second or third layer of glass forms a regular array. In some embodiments, wherein the areas of contact of the third phase of the second heterogeneous interlayer with the first, second or third layer of glass forms an irregular array.

[0039] In some embodiments, the second heterogeneous interlayer is a phase separating polymer that has separated to form at least two phases.

[0040] In some embodiments, wherein the surface of the first or second, and third glass layer is treated with an adhesion promoter to improve the adhesion with the heterogeneous interlayer.

[0041] In some embodiments, the first heterogeneous layer is deposited using 3-D printing, extrusion, roll-coating, offset-printing, spraying or infiltration. In some

embodiments, the second heterogeneous layer is deposited using 3-D printing, extrusion, roll- coating, offset-printing, spraying or infiltration.

[0042] In some embodiments, wherein the first heterogeneous interlayer is directly deposited on the first or second layer of glass. In some embodiments, the second

heterogeneous interlayer is directly deposited on the first, second, or third layer of glass.

[0043] In some embodiments, the first heterogeneous interlayer is fabricated separately and then applied to the first or second layer of glass to form an adhesive bond. In some embodiments, the second heterogeneous interlayer is fabricated separately and then applied to the first, second or third layer of glass to form an adhesive bond.

[0044] In some embodiments, the first and second phases of the first heterogeneous interlayer are applied simultaneously. In some other embodiments, the first and second phases of the first heterogeneous interlayer are applied sequentially.

[0045] In some embodiments, the third and fourth phases of the second heterogeneous interlayer are applied simultaneously. In some other embodiments, the third and fourth phases of the second heterogeneous interlayer are applied sequentially. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The following figures are provided for the purpose of illustration only and are not intended to be limiting.

[0047] FIGURE 1 shows a perspective view of the hybrid glass in accordance with one or more embodiments of this disclosure;

[0048] FIGURE 2 shows a schematic cross section of the hybrid film illustrating the areas of contact of the first phase of the first heterogeneous interlayer and the areas of contact of the second phase of the first heterogeneous interlayer with the first layer of glass or second layer of glass;

[0049] FIGURE 3 shows a schematic of a structure in cross-section with a second heterogeneous interlayer disposed on the second layer of glass in a structure shown in

FIGURE 1, and a third layer of glass disposed on top of the second heterogeneous interlayer according to one or more embodiments;

[0050] FIGURE 4 shows a schematic of patterning with an imprint head according to one or more embodiments;

[0051] FIGURE 5 shows a schematic of patterning with direct printing according to one or more embodiments;

[0052] FIGURE 6 shows the cracks formed after impacts in a sample having an area with a heterogeneous interlayer sandwiched between two layers of glass (top half), and a uniform homogeneous interlayer sandwiched between the glass layers (bottom half); and

[0053] FIGURE 7 shows extreme damage tolerance offered by the hybrid glass according to this disclosure.

DETAILED DESCRIPTION

[0054] A novel glass laminate composite that achieves both damage localization and toughness, enabling multi-hit capability, while maintaining high levels of global optical transparency is described. Methods for producing this novel glass laminate are also described. These fabrication techniques have ease of implementation, are cost-effective, scalable, and can be integrated with current composite material synthesis processes.

[0055] FIGURE 1 shows a schematic of the hybrid glass in accordance with this disclosure. The hybrid glass 100 includes a first layer of glass 101, a second layer of glass 102, and a first heterogeneous interlayer 103. The first heterogeneous interlayer 103 includes at least a first phase 131 and a second phase 132. The first phase 131 has a measured value of a property, such as but not limited to, Young's modulus, fracture strength, fracture toughness, storage modulus, loss modulus, elastic modulus, hardness and interfacial adhesion strength, greater than that of the second phase 132.

[0056] In this disclosure the measured value of a property of the first phase 131 and the second phase 132 refer to the values measured in a standard test using samples of free standing films of the materials used for the first phase 131 and the second phase 132.

Suitable standard tests that may be used for evaluation of the properties of the first and second phase 131 and 132 of the heterogeneous interlayer 103 may be selected from, but not limited to, tensile test, dynamic mechanic analysis (DMA), nanoindentation, dynamic nanoindentation, shore hardness test, Rockwell hardness test, Vickers hardness test, Brinell hardness test, microhardness test, such as, Knoop hardness test. In certain embodiments, when the second phase 132 is air or a liquid, it is assumed that the property of the first phase 131 is greater than that of the second phase 132. In other embodiments, when the first phase 131 and the second phase 132 result from the phase separation of the material used to form the heterogeneous interlayer 103, in-situ measurements of the properties of the materials resulting in the formation of the first and second phases 131 and 132 may be carried out after the phase separation has occurred using techniques such as, but not limited to,

nanoindentation, dynamic nanoindentation, microhardness testing etc. One of ordinary skill in the art will easily recognize that other techniques of quantifying the properties of the first phase 131 and the second phase 132 may be used as well.

[0057] Additionally, the first phase 131 and second phase 132 of the first heterogeneous interlayer 103 form an area of contact with the first layer of glass 101 and the second layer of glass 102. Furthermore, at least one of the first phase 131 and second phase 132 of the first heterogeneous interlayer 103 forms an adhesive bond with the first layer of glass lOland the second layer of glass 102. In some embodiments, the adhesive bond formed between at least one of the first phase 131 and second phase 132 of the heterogeneous interlayer 103 results in the transmission of the impact energy from the glass layers to the heterogeneous interlayer. Additionally, during crack propagation, the adhesive bond may also assist in arresting the crack propagation. FIGURE 2 shows a schematic cross section of the hybrid film illustrating the areas of contact 111 of the first phase 131 of the first heterogeneous interlayer 103 and the areas of contact 112 of the second phase 132 of the first heterogeneous interlayer 103 with the first layer of glass 101 or second layer of glass 102.

[0058] In some embodiments, the hybrid glass further includes a second heterogeneous interlayer 104 disposed over the first layer of glass 101 or second layer of glass 102.

FIGURE 3 shows a schematic of a hybrid glass 300 where a second heterogeneous interlayer 104 is disposed on the second layer of glass 102 of a structure similar to the ones shown in FIGURE 1. FIGURE 3 additionally shows a third layer of glass 105 disposed over, the second heterogeneous interlayer 104. The second heterogeneous interlayer 104 includes at least a third phase 141and a fourth phase 142. In some embodiments, the third phase 141 has a measured value of a property, such as but not limited to, Young's modulus, fracture strength, fracture toughness, storage modulus, loss modulus, elastic modulus, hardness and interfacial adhesion strength greater than that of the fourth phase 142.

[0059] In this disclosure the measured value of a property of the third phase 141 and the second phase 142 refer to the values measured in a standard test using samples of free standing films of the materials used for the third phase 141 and the fourth phase 142.

Suitable standard tests that may be used for evaluation of the properties of the third and fourth phase 141 and 142 of the heterogeneous interlayer 104 may be selected from, but not limited to, tensile test, DMA, nanoindentation, dynamic nanoindentation, shore hardness test, Rockwell hardness test, Vickers hardness test, Brinell hardness test, microhardness test, such as, Knoop hardness test. In certain embodiments, when the second phase 142 is air or a liquid, it is assumed that the property of the third phase 141 is greater than that of the fourth phase 142. In other embodiments, when the third phase 141 and the fourth phase 142 result from the phase separation of the material used to form the heterogeneous interlayer 104, in- situ measurements of the properties of the materials resulting in the formation of the first and second phases 141 and 142 may be carried out after the phase separation has occurred using techniques such as, but not limited to, nanoindentation, dynamic nanoindentation,

microhardness test etc. One of ordinary skill in the art will easily recognize that other techniques of quantifying the properties of the third phase 141 and the fourth phase 142 may be used as well.

[0060] Additionally, the third phase 141 and fourth phase 142 of the second

heterogeneous interlayer 104 forms a point of contact with the second layer of glass 102, and the third layer of glass 105. Additional layers of glass and heterogeneous layers are contemplated.

[0061] In some embodiments, when the second heterogeneous interlayer is disposed on the first layer of glass 101, the third phase 141 and a fourth phase 142 of the second heterogeneous interlayer 104 form a point of contact with the first layer of glass 101, and third layer of glass 105. Furthermore, at least one of the third phase 141 and fourth phase 142 of the second heterogeneous interlayer 104 forms an adhesive bond with the first layer of glass 101 or the second layer of glass 102, and the third layer of glass 105. In some embodiments, the adhesive bond formed between at least one of the third phase 141 and second phase 142 of the second heterogeneous interlayer 104 results in the transmission of the impact energy from the glass layers to the heterogeneous interlayer 104. Additionally, during crack propagation, the adhesive bond may also assist in arresting the crack

propagation.

[0062] In some embodiments, one or more of the first glass layer 101, second glass layer 102, the optional third glass layer 105, the first heterogeneous interlayer 103, and the optional second heterogeneous interlayer 104 are transparent. In some other embodiments, one or more of t the first glass layer 101, second glass layer 102, the optional third glass layer 105, the first heterogeneous interlayer 103, and the optional second heterogeneous interlayer 104 are index-matched.

[0063] In some embodiments, the first phase 131 of the first heterogeneous interlayer 103 includes a first polymeric adhesive which forms a discontinuous region in the interlayer. In some other embodiments, the second phase 132 of the first heterogeneous interlayer 103 includes a second polymeric adhesive which forms a discontinuous region in the interlayer. In some embodiments, the first phase 131 of the first heterogeneous interlayer 103 includes a first polymeric adhesive which forms a continuous region in the interlayer. In some other embodiments, the second phase 132 of the first heterogeneous interlayer 103 includes a second polymeric adhesive which forms a continuous region in the interlayer. [0064] In some embodiments, the second phase 132 of the first heterogeneous interlayer 103 is air or a liquid. In some embodiments, the fourth phase 142 of the second

heterogeneous interlayer 104 is air or a liquid.

[0065] In some embodiments, the discontinuous regions of the first phase 131 and the second phase 132 of the first heterogeneous interlayer 103 form an interpenetrating network. In some embodiments, the discontinuous regions of the optional third phase 141 and the optional fourth phase 142 of second heterogeneous interlayer 104 form an interpenetrating network.

[0066] In some embodiments, the areas of contact 111 of the first phase 131 of the first heterogeneous interlayer 103 with the first layer of glass 101 or second layer of glass 102 forms a regular array. In some other embodiments, the areas of contact of the first phase 111 of the first heterogeneous interlayer 103 with the first layer of glass 101 or second layer of glass 102 forms an irregular array. In some embodiments, the areas of contact 113 of the optional third phase 141 of the second heterogeneous interlayer 104 with the first layer of glass 101, the second layer of glass 102 or third layer of glass 105 forms a regular array. In some other embodiments, the areas of contact 112 of the optional third phase 141 of the second heterogeneous interlayer 104 with the first layer of glass 101, second layer of glass 102 or third layer of glass 103 forms an irregular array. In some embodiments, the pattern of the contact 112 can be the same pattern for the contact 111. In some other embodiments, the pattern of the contact 112 can adopt a different pattern, in terms of distribution, array pattern and density, in comparison to that of contact 111.

[0067] In some embodiments, one or more of the first phase 131 and second phase 132 of the first heterogeneous interlayer 103 and the optional third phase 141 and fourth phase 142 of the second heterogeneous interlayer 104 is made of thermosetting resin. In some embodiments, one or more of the first phase 131 and second phase 132 of the first heterogeneous interlayer 103 and the optional third phase 141 and fourth phase 142 of the second heterogeneous interlayer 104 is made of thermoplastic resin. Some suitable resins that can be used are acrylics, epoxies, polyurethanes, urea formaldehyde resins, phenolic resins and novolacs. However, as discussed above, while selecting the resins as candidates for the first phase 131 and the second phase 132, or the option third phase 141 and the optional fourth phase 142, it must be ensured that the first phase 131 and the optional third phase 141 have a measured value of a property, such as but not limited to, Young's modulus, fracture strength, fracture toughness, storage modulus, loss modulus, elastic modulus, hardness and interfacial adhesion strength, greater than that of the second phase 132 and optional fourth phase 142, respectively. Additionally, in some embodiments the second phase 132, or the optional fourth phase 142, is air or a liquid.

[0068] In some embodiments, one or more of the first heterogeneous interlayer 103 or the optional second heterogeneous interlayer 104 is a phase separating polymer that has separated to form at least two phases. In some embodiments, the phase separating polymer is a blend of homopolymers that eventually phase separate out after application. In some embodiments, the phase separating polymer is a block copolymer. In some other embodiments, the block copolymer can microphase separate to form periodic nanostructures, as found in styrene- butadiene-styrene block copolymer. One skilled in the art would easily recognize other combinations of copolymer blocks can be combined to form the block copolymer. In some embodiments, one of the copolymer block used is a vinylaromatic monomer. In some other embodiments, one of the copolymer blocks used is a diene. Some suitable vinylaromatic monomers that can be used are styrene, alpha-methylstyrene, ring-alkylated styrenes, such as p-methylstyrene, or tert-butyl styrene, or 1,1-diphenylethylene, or a mixture thereof. Some suitable dienes that may be used are butadiene, isoprene, 2,3-dimethylbutadiene, 1,3- pentadiene, 1,3-hexadiene, or piperylene, or a mixture of these.

[0069] In some embodiments, the first glass layer 101, the second glass layer 102, or the optional third glass layer 105 is made of silicate glass. Some of the common types of silicate glasses that can be used are, fused quartz, soda-lime-glass, sodium borosilicate glass, lead- oxide glass, aluminosilicate glass and oxide glass. Other types of specialty glass such as sapphire glass, toughened or tempered glass are also envisaged to be within the scope of this disclosure.

[0070] In some embodiments, the first heterogeneous interlayer 103 and the optional second heterogeneous interlayer 104 are made of the same material. In some other embodiments, the first heterogeneous interlayer 102 and the optional second heterogeneous interlayer 104 are made of materials with different composition.

[0071] In some embodiments, the surface of one or more of the first layer of glass 101 and the second layer of glass 102 or the optional third layer of glass 103 is treated with an adhesion promoter to improve the adhesion of the surface of the glass with the first and the second heterogeneous interlayers, 103 and 104, respectively.

[0072] In an exemplary embodiment, an adhesion promoting treatment for treating the surface of the glass is a coating deposited using a solution of hydrolyzed organofunctional silane. Suitable organofunctional silanes can be selected based on the type of material used in the first and second heterogeneous interlayers, 103 and 104, respectively. In some other embodiments, organometallic coupling agents can be used to treat the surface of the glass to improve the adhesion of the heterogeneous interlayer with the glass. Some suitable coupling agents are titanates, zirconates, and zircoaluminates. The bonding of the interlayers may be optimized by matching the functionality on the coupling agent selected with the type of material used for in the first and second heterogeneous interlayers, 103 and 104, respectively.

[0073] In an aspect a method of manufacturing a hybrid glass includes, providing a first layer of glass; providing a second layer of glass; providing a first heterogeneous interlayer disposed in between the first layer of glass and the second layer of glass; wherein the first heterogeneous interlayer comprises at least a first and a second phase, wherein the first phase has a measured value of a property greater than that of the second phase, wherein the property is selected from a group consisting of Young's modulus, fracture strength, fracture toughness, storage modulus, loss modulus, elastic modulus, hardness and interfacial adhesion strength; applying the first layer of heterogeneous interlayer material on the first or second layer of glass; wherein the first and second phases of the first heterogeneous interlayer form a point of contact with the first and second layer of glass; and wherein at least one of the first phase and the second phase of the first heterogeneous interlayer forms an adhesive bond with the first and second layer of glass.

[0074] In certain embodiments, an imprint head can be used for deposition of the first heterogeneous interlayer. For example, an array of mm-sized cylinders, where the size, height, spacing, and distribution of these cylinders are adjusted depending on specific applications. FIGURE 4 shows a schematic of patterning with an imprint head 400 with the cylindrical protrusions 401. First, the imprint head is brought in contact with the uncured resin 402. Upon release, the uncured resin 402 is adhered to the tips of the cylindrical protrusions 401, to form the beads 403 attached to the tips of the cylindrical protrusions 401. Thereafter, the uncured first heterogeneous interlayer material is transferred onto the surface of a first glass sheet 404 to form an imprinted glass sheet 405. After releasing the imprint head, a second glass sheet 406 is placed onto the imprinted glass sheet 405, forming a glass- resin-glass laminate structure 407.

[0075] In some embodiments, the resin coating is a phase separating polymer that segregates into two phases. In such instances it may be necessary to only apply one resin coating and form the first phase and second phase in-situ on the glass during curing. In some other embodiments, after curing the first resin liquid, another resin is allowed to fill at least some of the vacant space of the interlayer. In certain embodiments, the filling of the spaces in the interlayer is facilitated by capillary action. The second resin is cured once the infiltration of the resin is achieved to a desired level. In some embodiments, the infiltration completely fills up all the vacant space left between the two glass layers.

[0076] FIGURE 5 shows a schematic of patterning with direct printing. In this case, the pattern of the uncured resin 501 is printed on a glass surface 502 with a printing nozzle 503, which controls the volume, geometry, and position of the droplets in a customizable fashion. In some embodiments, the subsequent steps of fabrication are similar to those discussed above. In certain embodiments, a 3-D printer is used for depositing the heterogeneous interlayer.

[0077] In some embodiments, more than one printing head is used simultaneously to deposit the materials that forms the heterogeneous interlayer. For example, when 3D printing is being used for the deposition of the material for the heterogeneous interlayer including more than one adhesive resin, more than one separate head could be used to deposit the separate adhesive simultaneously in one pass. In another embodiment, sequential passes are used to deposit the adhesives one by one.

[0078] One skilled in the art would appreciate that using such modern additive manufacturing tools, one can deposit extremely intricate geometries with spatial variation in composition of matter to tailor the properties of the heterogeneous interlayer as required. More specifically, to control the location and areas of the point of contact of the resin with the glass layers and alter the mechanical properties of the final heterogeneous interlayer.

[0079] When a crack is initiated from an impact to the glass it propagates. For example, referring to FIGURE 2, when a crack is initiated in either of the first or second glass layers 101 or 102, it continues to propagate in the glass layer. During the propagation of the crack, the leading edge of the crack, e.g., the crack, tip at the interface formed between the first or second glass layers 101 or 102 and the heterogeneous interlayer 103 encounters a change in the region of area of contact 112 to 111. Upon encountering this change in the area of contact, the crack propagation is arrested. Without being bound by theory, it is believed that the crack propagation is arrested because the stress field at the crack tip is changed when the contact region changes from 112 to 111 due to the change of material properties. The stress intensity factor in the glass layer is greatly reduced as more load is transferred to the stronger phase 131 which forms stronger contact 111 with glass layers. In this case, the relevant material properties for phase 131 and 132 include but are not limited to Young's modulus, fracture strength, fracture toughness, storage modulus, loss modulus, elastic modulus, hardness and interfacial adhesion strength to the glass layers. This phenomenon can be clearly seen in the samples shown in FIGURE 6. The top part of the FIGURE 6 shows an area having a heterogeneous interlayer sandwiched between two layers of glass, in accordance with this disclosure. In contrast, the bottom part of the same sample has a uniform homogeneous interlayer sandwiched between the glass layers. Upon similar impacts, the bottom portion of the specimen, where homogeneous interlayer is present, shows radial cracks having lengths significantly larger than the cracks formed upon impact in the area where homogeneous interlayer is present.

[0080] Additionally, the specimen also shows ability to take several impacts in a small region. Without being bound to the theory, it is anticipated that due to lack of formation of large cracks, intersection of cracks is avoided. This is expected to significantly improve the endurance to damage for these hybrid glasses. FIGURE 7 shows the extreme damage tolerance offered by the hybrid glass according to this disclosure. Shown is sample of 50 x 70 mm which has endured around 20 impacts. The zone of crack propagation is limited to the epicenter of the impact and much of the energy of impact is absorbed by the heterogeneous layers and not expended in long radial crack propagation. This phenomenon enables large areas of undamaged glass to remain intact after several impacts.

[0081] The above described properties may be of significant importance in defense related applications. Considering the example of the hybrid glass as a potential replacement material for a visor or windshield, upon impact the hybrid glass can remain functional for longer durations without impairing the field of view entirely. Additionally, the localization of the crack propagation eliminates the possibility of long cracks intersecting upon subsequent impacts. This enhances the durability of the hybrid glasses in these applications. Similar advantages can be expected to be realized in other applications where visibility through the glass and mechanical integrity of the structure may be compromised due to long range crack propagation. Some applications requiring these properties are windows, windshields, sunroofs, skylights, display cases, picture frames, and personal electronic devices, such as tablets and smartphones.

[0082] Upon review of the description and embodiments of the present invention, those skilled in the art will understand that modifications and equivalent substitutions may be performed in carrying out the invention without departing from the essence of the invention. Thus, the invention is not meant to be limiting by the embodiments described explicitly above, and is limited only by the claims which follow.