WO2019245819A1

WO2019245819A1 - Glass laminate construction with controlled breakage for pedestrian safety

Info

Publication number: WO2019245819A1
Application number: PCT/US2019/036746
Authority: WO
Inventors: Thomas Michael Cleary; James Gregory Couillard; Petr GORELCHENKO; Jason Thomas HARRIS; Douglas Earl HARSHBARGER; Jr. Louis Mattos; Elias MERHY
Original assignee: Corning Incorporated
Priority date: 2018-06-22
Filing date: 2019-06-12
Publication date: 2019-12-26

Abstract

A glass laminate includes an outer glass sheet having a first outer surface and a second inner surface, an inner glass sheet having a third outer surface and a fourth inner surface, and a polymer interlayer between the outer glass sheet and the inner glass sheet. At least one of the inner glass sheet and the outer glass sheet has a thickness of about 2 mm or less. At least one of the inner glass sheet and the outer glass sheet includes a plurality of fracture-initiation points in a predetermined pattern designed to weaken the glass laminate in the event of a predetermined external impact on the first outer surface.

Description

GLASS LAMINATE CONSTRUCTION WITH CONTROLLED BREAKAGE FOR

PEDESTRIAN SAFETY

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S.

Provisional Application Serial No. 67/688,551 filed on June 22, 2018 the content of which is relied upon and incorporated herein by reference in its entirety.

FIELD

[0002] The present disclosure relates generally to glass laminates, and more particularly to laminates with chemically-strengthened glass layers having low weight, high strength and a specific breakage performance in the event of a pedestrian impact.

BACKGROUND

[0003] Glass laminates can be used as windows and glazing in architectural and vehicle or transportation applications, including automobiles, rolling stock, locomotives, watercraft, and airplanes. As used herein, a glazing or a laminated glass structure is a transparent, semi transparent, translucent or opaque part of a window, panel, wall, enclosure, cover, sign or other structure. Common types of glazing that are used in appliance, architectural and vehicle applications include clear and tinted laminated glass structures.

[0004] Conventional automotive glazing constructions may consist of two plies of soda lime glass (heat treated or annealed) with a thickness of 2 mm or more and with a polyvinyl butyral PVB interlayer between the two plies. These laminate constructions have certain advantages, including low cost, and a sufficient impact resistance for automotive and other applications. However, because of their limited impact resistance, these laminates usually have a poor behavior and a higher probability of breakage when getting struck by roadside stones, vandals and other impacts. In addition, fuel economy is a function of vehicle weight in many vehicles. It is desirable, therefore, to reduce the weight of glazings for such applications without compromising their strength and sound-attenuating properties.

[0005] In view of the foregoing, so-called hybrid glazings or glass laminates have been introduced that use a chemically-strengthened glass layer in place of at least one of the soda lime glass layers of conventional glazings or glass laminates. These hybrid laminates possess or exceed the durability, sound-damping and breakage performance properties associated with thicker, heavier glazings, and can be lighter due to using a thinner chemically- strengthened glass layer in place of the relatively thick soda lime layer in conventional laminates.

[0006] However, another important factor in considering vehicle glazing is the safety and protection of not only the vehicle occupants, but also pedestrians and cyclists— so-called vulnerable road users (VRU)— who may be involved in pedestrian-vehicle collisions. As used herein,“pedestrian” may refer to any type of VRU, whether they are persons on-foot or on a bicycle, for example. During most pedestrian-vehicle collisions, the front of the vehicle (e.g., front bumper or grill) first collides with the pedestrian, and the body of the pedestrian wraps around the front shape of the vehicle (e.g., the shape defined by the bumper, hood or bonnet, and front windshield). This wrapping of the body around the shape of the vehicle results in a high probability that the head of the pedestrian will strike one or more particular areas of the vehicle, including the windshield. In some cases, this wrapping of the body results in a head impact at high velocity to a whiplash effect of the body around the shape of the vehicle. The severity and location of impact is determined by many factors, including vehicle shape and height of the pedestrian, which are used to determine a so-called wrap around distance (WAD). The WAD is used to determine likely areas of head impact in a pedestrian-vehicle collision, and these areas may include, for example, at least part of the windshield, particularly the lower part of the windshield nearest the hood or the sides of the windshield.

[0007] While the above-discussed hybrid glazings or laminates can have improved durability and breakage properties with respect to, for example, impacts between hail or stones and the windshield, the toughness of such laminates can have undesirable breakage performance in the event of a collision between a pedestrian and a windshield, for example.

[0008] So-called“pedestrian protection” or“ped-pro” considerations demand that the energy of a collision between a pedestrian and the vehicle is dissipated to a degree so that the risk of injury to the pedestrian is reduced. For example, energy could be dissipated when a windshield breaks upon impact with the pedestrian. To encourage pedestrian safety, the EURO-NCAP (European New Car Assessment Programme) commits automotive OEMs commercializing their vehicles in Europe to pass pedestrian protection tests, which measure performance in terms of a Head Injury Criterion (HIC) value. Pedestrian protection tests are not part of standard regulations at this time, but it is believed that they likely will be by 2024. Automotive OEMs still need to comply to targets to achieve high ratings with insurers, as the testing is part of determining the“5 star” safety rating.

[0009] Conventional windshields made of two plies of relatively thick annealed soda- lime glass (ASLG) may yield and break accomplishing this goal; however, their performance is highly variable and the industry has struggled to consistently achieve the desired HIC targets which can result in reduced safety ratings for the vehicle. On the other hand, hybrid glazings that include a chemically strengthened layer may not yield or break quickly enough (or at all) in the event of a pedestrian impact. For all windshields, a region within 165 cm of the periphery is particularly difficult to achieve this target due to the rigidity of the laminate in those areas (due to curvature and edge effects). The primary approach to achieve low HIC values is to have both plies of the glass fracture and then the PVB inter-layer stretches to absorb the impact. The challenge is that sometimes one or both plies of glass do not reliably fracture or do not fracture quickly enough to safely dissipate the impact energy, and thus result in high HIC values.

[0010] In view of the foregoing, improved glazings or glass laminates that are thin, light, and durable against certain impacts but that have optimized breakage in the event of a pedestrian impact are desired.

SUMMARY

[0011] In certain applications, it is desirable for glass laminates having a high or maximized impact resistance to impacts on an external side of the laminate (external impacts), in order to resist the impact of stones, hail or vandals, for example, while safely minimizing or dissipating the energy of a pedestrian striking the windshield to reduce risk of injury to the pedestrian in a vehicular accident.

[0012] According to one aspect of the present disclosure, a glass laminate includes an outer glass sheet having a first outer surface and a second inner surface, an inner glass sheet having a third outer surface and a fourth inner surface, and a polymer interlayer between the outer glass sheet and the inner glass sheet. At least one of the inner glass sheet and the outer glass sheet has a thickness of about 2 mm or less, and at least one of the inner glass sheet and the outer glass sheet includes a plurality of fracture-initiation points in a predetermined pattern, the predetermined pattern being designed to weaken the glass laminate in the event of a predetermined external impact on the first outer surface. In some aspects, the predetermined external impact is a pedestrian head or headform impact and the laminate is be a vehicle glazing or windshield.

[0013] The fracture-initiation points may include at least one of the following: flaws or defects within at least one of the inner glass sheet and the outer glass sheet; or flaws or defects on at least one of the first outer surface, the second inner surface, the third outer surface, or the fourth inner surface. The flaws or defects may include at least one of a coating, a particle, a surface imperfection, a locally annealed region, a locally laser-ablated region, or a locally weakened area on at least one of the first outer surface, the second inner surface, the third outer surface, or the fourth inner surface.

[0014] In some aspects hereof, the fracture-initiation points are arranged so that fracture of the glass laminate is initiated within a time of about 3 ms from a predetermined impact on the first surface. In another aspect, the time is within about 2 ms.

[0015] In an aspect hereof, at least one of the inner glass sheet and the outer glass sheet may be chemically strengthened. In some aspects, the inner glass sheet may have a thickness of 2 mm or less and is chemically strengthened. In additional aspects, the outer glass may have a thickness of about 1.5 mm or greater and is not chemically strengthened. The outer glass sheet may include soda lime glass. In another aspect, the inner glass sheet has a thickness not exceeding 1.5 mm, not exceeding 1.0 mm, or not exceeding 0.7 mm

[0016] In another aspect hereof, a vehicle includes the glass laminate of the above aspects. The laminate may be a windshield of the vehicle. In some aspects, windshield achieves a Head Impact Criteria (HIC) value of less than 650, less than 550, or less than 550.

[0017] In another aspect hereof, a method of producing a glass laminate having optimized breakage for improved pedestrian safety includes: providing a first glass sheet and a second glass sheeting; laminating the first and second glass sheets together with a polymer interlayer therebetween to form a glass laminate, the first glass sheet being an outer glass sheet of the glass laminate and including a first outer surface and a second inner surface, and the second glass sheet being an inner glass sheet of the resulting glass laminate and including a third outer surface and a fourth inner surface. The method further includes creating one or more fracture-initiation points on at least one of the third outer surface and the fourth inner surface, where the fracture -initiation points are arranged to cause fracture of the glass laminate in response to a predetermined impact on the first outer surface. The predetermined impact is an impact between a pedestrian’s head or a headform and the first outer surface. According to some aspects, the creating of the one or more fracture-initiation points includes at least one of the following: applying a coating to the third outer surface or the fourth inner surface, forming a surface imperfection in the third outer surface or the fourth inner surface, locally annealing a region of the second glass sheet, and locally weakening a region of the third outer surface or the fourth inner surface.

[0018] Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings. It is to be understood that both the foregoing general description and the following detailed description present embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention and together with the description serve to explain the principles and operations of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Fig. 1 is a schematic cross-sectional illustration of a portion of a laminated glass structure according to an embodiment of this disclosure;

[0020] Fig. 2 is a schematic cross-sectional illustration of a portion of a laminated glass structure experiencing an impact according to an embodiment of this disclosure;

[0021] Fig. 3 is a plan view of the laminated glass structure of Fig. 2 according to an embodiment of this disclosure;

[0022] Fig. 4 is a schematic cross-sectional illustration of an embodiment of controlled flaws formed in the outer surface of the inner glass sheet of a laminate as illustrated in Fig. 1 according to an embodiment of this disclosure; [0023] Fig. 5 is a schematic cross-sectional illustration of an embodiment of controlled flaws formed in the inner surface of the inner glass sheet of a laminate as illustrated in Fig. 1 according to an embodiment of this disclosure;

[0024] Fig. 6 is a schematic illustration of a windshield having areas with controlled flaws according to an embodiment of this disclosure;

[0025] Fig. 7 is a schematic illustration of a windshield having controlled flaws form in a pattern according to an embodiment of this disclosure;

[0026] Fig. 8 is a schematic illustration of a windshield having controlled flaws form in another pattern according to an embodiment of this disclosure;

[0027] Fig. 9 is a schematic illustration of a windshield having controlled flaws form in another pattern according to an embodiment of this disclosure;

[0028] Fig. 10 is a schematic illustration of a windshield having controlled flaws form in another pattern according to an embodiment of this disclosure;

[0029] Fig. 11 is a plot of surface compressive stress in a chemically strengthened glass sheet that has been selectively weakened according to an embodiment of this disclosure;

[0030] Fig. 12 is a schematic illustration of points on a vehicle for which HIC values are tested;

[0031] Fig. 13 is a schematic illustration of the hood and windshield of a vehicle showing wrap around distances for measuring HIC values;

[0032] Fig. 14 is a schematic illustration of vehicle showing the boundaries of an area for which HIC values are tested;

[0033] Fig. 15 is a schematic illustration of a vehicle windshield for which a boundary region is tested for HIC performance;

[0034] Fig. 16 is a schematic illustration of a headform impact used in testing HIC performance.

DETAILED DESCRIPTION

[0035] Embodiments disclosed herein are directed to laminated glass articles for vehicular glazings or windshields having controlled glass breakage in certain types impacts, and methods of making the same. In particular, embodiments disclosed herein are directed to glass laminates having controlled glass breakage in the event of an impact with a pedestrian so as to reduce or minimize the risk of injury to the pedestrian resulting from the pedestrian impacting the glazing or windshield. Such controlled breakages can result from an impact with the head of a pedestrian or a headform used in vehicular safety testing for measuring HIC. Thus, the articles and methods disclosed herein provide glass laminates having lower HIC values than are otherwise achieved. For example, embodiments of this disclosure can achieve a HIC value of less than 650. At least some embodiments herein are applicable to conventional vehicle or automotive glazings. Some embodiments are directed to laminates that are thinner than the laminates used in conventional automotive glazing.

[0036] The strength and mechanical impact performance of a glass sheet or laminate can be affected by defects or flaws in the glass, including both surface and internal defects. For this reason, accidental or naturally occurring defects and flaws in the glass are normally undesirable as the flaws may be an initiation site for glass failure due to stress concentrations at or around the flaw. However, embodiments of this disclosure include glass articles or laminates with flaws specifically designed to allow the article or laminate to fail in a desired manner. For example, such a glass article may be incorporated into a windshield with breakage performance designed to protect pedestrians or improve performance in HIC testing. The terms“flaw” and“defect” may be used interchangeably herein, but unless otherwise noted are not intended to refer to natural or accidental flaws or defects resulting from typical manufacturing or handling processes, or from damage created during normal use, but rather refer to designed or engineered features formed on or in glass articles to achieve the desired breakage performance.

[0037] The mechanics of an impact on a glass sheet, and the mechanics of failure or breakage, can be understood in terms of the state of tension or compression that the glass article is subjected to upon impact. For example, for a glass sheet having first and second opposing surfaces, an impact on the first surface can put the point of impact on the first surface into compression. Meanwhile, a ring or“hoop” around the impact point may be put into tension (so-called“hoop stress”), and the second surface may also be put into tension.

[0038] If a flaw in the glass is put into tension, the cracks may propagate and the glass break. Typically, the origin of failure in the glass article will be at a flaw, usually on the glass surface at or near the point of highest tension. This may occur on the face opposite to the impact, but it can also occur along the region of hoop stress. In either case, if a flaw in the glass is put into tension during an impact event, the flaw will likely propagate, and the glass will typically break. With this in mind, embodiments herein include glass articles that use specifically designed flaws to cause such breakage in response to predetermined type of impact, such as a collision with a headform or head of a pedestrian, while the glass articles resist breakage for other types of impact, such as a stone strike or hail impact.

[0039] A laminated article having multiple glass sheets has multiple glass surfaces in various states of compression or tension. The precise state of a particular surface depends on a number of factors, including the number and thicknesses of layers and the position of that surface within the stack of the laminate. Embodiments and examples herein may use a laminate having two glass sheets with an interlayer between the glass sheets. However, this disclosure is not limited to this particular laminate construction, and contemplates laminated articles having two or more layers with one or more interlayers therebetween. The failure of a laminated article may be similar to that discussed above for a glass sheet. That is, when a glass laminate is impacted, the impact point is put into compression, while a region around the impact point experiences hoop stress (tension). The opposite face of the impacted laminate may also be put into tension.

[0040] The improved breakage can be expressed as an increased probability of the glass laminate breaking when impacted by a pedestrian’s head or a headform. The defects or flaws are designed so that the risk of breakage due to other types of impacts, such as a rock strike or hail, is minimized. The risk of such unwanted breakage may be minimized by controlling aspects of the points of fracture initiation, including size, spacing, shape of individual points, pattern of multiple points, depth, or location on or in a glass sheet. For example, as discussed in more detail below, a pattern of fracture -initiation points can be designed so that a particular mechanical loading (such as that from the head of a pedestrian or from a headform) on the laminate will cause controlled breakage of the laminate, while other or more minor impacts will be less likely to cause breakage. For example, the pattern can be designed so that breakage initiates within a certain time from the targeted impact (i.e., a pedestrian or headform impact). By initiating breakage within a certain time, the risk of injury to a pedestrian can be decreased. In particular, it is desirable for breakage to occur as soon as possible upon a head impact event to maximize energy dissipation via, for example, glass cracking and stretching of the polymer interlayer.

[0041] According to some embodiments, glass laminates have one or more points of fracture initiation (or flaws) specifically arranged to have improved breakage when a pedestrian’s head (or a headform used in safety testing) impacts an exterior surface of the glass laminate on the outside of the vehicle. The arrangement of flaws can be located in one or more specific areas of the laminate, such as areas corresponding to areas of a windshield likely to be struck by a pedestrian in a collision, or areas of a windshield that are tested to measure HIC values. In addition, the individual points of fracture initiation can be arranged relative to one another (i.e., in a pattern) to trigger the desired breakage behavior. For example, a plurality of flaws may be arranged in a grid, where the spacing of the lines in the grid is designed to be preferentially triggered by an impact from a head or headform, but not from smaller impacts. The plurality of flaws may also be arranged in shapes such as rectangles, circles, or ovals, where the size of the shapes is designed to be preferentially triggered by an impact from a head or headform, but not from smaller impacts. For example, the spacing of a grid or the size of a shape of the flaws may be large enough that the stress field or tension resulting from an impact with a smaller object (such as a stone or hail, for example) is not likely to reach the position of a flaw, but the same resulting from a collision with a head or headform is likely or guaranteed to reach the position of the flaw.

[0042] According to some embodiments, the glass laminate includes two sheets of relatively thin annealed glass. In some embodiments, the glass laminate includes a thin inner glass sheet of strengthened glass. The outer glass sheet can be non-strengthened or annealed glass. In some embodiments, the strengthened inner glass sheet is chemically strengthened via an ion exchange process as described in more detail hereinafter. In some embodiments, the glass may be strengthened through a glass laminate process whereby coefficient of thermal expansion (“CTE”) mismatch from the core of the glass to the surface of the glass creates a compressive zone at the surfaces.

[0043] As shown in Figure 1, a glass laminate 10 includes an outer glass sheet 11 having a first outer surface (a surface 1) and a second inner surface (a surface 2), an inner glass sheet 13 having a third outer surface (a surface 3) and a fourth inner surface (a surface 4), and a polymer interlayer 15, such as a polyvinyl butyral (PVB) interlayer, between the outer glass sheet 11 and the inner glass sheet 13. The fracture-initiation points can be located within at least one of the inner glass sheet 13 and the outer glass sheet 11; or on at least one of surface 1, surface 2, surface 3, or surface 4. In some particular embodiments, the fracture -initiation points are formed on surface 3 or surface 4.

[0044] Figure 2 shows the glass laminate 10 when impacted on surface 1 by a headform H, representing the head of a pedestrian or a headform used in safety testing, with a force of impact in the direction shown by the arrow F. The bending of the glass laminate 10 is not necessarily drawn to scale, but illustrates how surface 1 may be put into compression, while surface 4 may be put into tension. Figure 3 shows a plan view of the glass laminate 10 in Figure 2, where the point of impact P with the headform H is shown. In addition, the circle HS represents a region of hoop stress induced in the glass laminate from the impact. Hoop stress can be understood as a normal stress in the tangential direction of circle HS.

[0045] Figures 4 and 5 are illustrations of fracture-initiation points 17 formed in surface 3 and surface 4, respectively. The shape of the fracture-initiation points 17 in Figures 4 and 5 are not intended to be limiting to the type of flaw formed. The fracture-initiation can take various forms according to different aspects of the embodiments of this disclosure. For example, the points of fracture initiation may be one or more flaws in one or more of the glass sheets of the glass laminate, including localized damage or weakening formed in or on the glass. According to some embodiments, such flaws may be formed in or on a glass sheet through local annealing, laser ablation, scratches formed on a surface of the glass sheet, localized weakening during an ion exchange (“IOX”) process, or hard contact indentations. In addition, the points of fracture initiation may be formed by the presence of a material on a surface of the glass, such as a coating. The coating may have a modulus of elasticity that differs from that of the glass sheet to cause increased tension in the desired location that results in breakage. The coating may include particles that abrade, indent, scratch, or otherwise degrade the integrity of the glass sheet upon the specified impact.

[0046] In embodiments where the outer or inner glass sheet is chemically strengthened, the fracture-initiation points can be formed by localized weakening achieved via retarding the ion exchange process in certain locations. Locations where the ion exchange process is retarded may have reduced surface compressive stress (CS) or reduced depth of layer (DOL) of compressive stress. According to some embodiments, the ion exchange process can be retarded by screen-printing a pattern (such as a grid or a dot pattern) that at least partially blocks or slows the migration of ions in and out of the glass relative to areas where the pattern is not present. In some embodiments, a highly concentrated salt can be used to retard ion exchange in a desired pattern. However, other materials may be used, so long as they block or retard ion exchange with the underlying glass sheet. For example, tapes such as Kapton tape, which is heat resistant and easy to remove after IOX, can be used. Also, an alkali-containing paste can be used to form a pattern on the surface. For example, a paste with a combination of potassium sulfate and/or sodium sulfate can be used, which can act as the ion source for regions under the paste, and thus dictate the rate of IOX as compared to the rate in surrounding regions, which is controlled by the IOX bath. This material can be arranged in a controlled weakening pattern that is applied by screen-printing or inkjet printing, for example. However, aspects of embodiments may use any number of methods of applying such a material, including pen dispensing of liquid or paste materials, or using adhesive decals of solid masking materials, for example.

[0047] In some embodiments, the fracture-initiation points can be formed by locally annealing a glass sheet after the ion exchange process, which can reduce compressive stress in local areas of the glass sheet. Such localized annealing can be accomplished using high, concentrated heat. For example, a flame or laser can be used for local annealing.

[0048] In some embodiments, fracture-initiation points can be formed using a coating or material applied to a surface of a glass sheet. The material can be, for example, a high modulus material that has a higher modulus than the glass material of the glass sheet, such as a metallic frit enamel. Without wishing to be bound by theory, an aspect of some embodiments includes a high-modulus material or coating of a surface of a glass sheet, where, upon the specific impact, a fracture begins in the high-modulus material or coating and the fracture travels to and transfers into the glass surface. In some embodiments, the high-modulus coating can include an anti-reflective coating or an easy-to-clean coating. The coating could be applied in various patterns as discussed herein, including a dot pattern, a grid pattern of lines or dots, or in lines forming certain shapes, such as circles or ovals. In some embodiments, the coating can be applied over only a portion of a surface of the glass sheet or substantially all of the surface. [0049] According to some embodiments of this disclosure, the fracture-initiation points can be arranged in one or more patterns or areas according to the probability of a pedestrian head strike in a certain area of a vehicle windshield. For example, Figure 6 illustrates an automobile 18 with a windshield 20 according to a glass laminate. Fracture-initiation points are distributed in an area likely to be struck by pedestrian’s head, as shown by the shaded region 22. This region 22 may also correspond to one or more areas tested in ped-pro testing to determine HIC values. In various embodiments, the fracture-initiation points can be formed on one or more of surfaces 1-4. In some particular embodiments, the fracture- initiation points can be formed on surface 3 or surface 4, or on both surface 3 and surface 4, for example. In Figure 6, the shaded region 22 extends along the bottom side, the left side, and the right side of the windshield 20. These areas can correspond to areas where there is a higher probability of a pedestrian head strike. The extent or shape of this region can vary depending on a particular vehicle design, as the geometry of the vehicle (including, for example, the bumper height, hood length, and shape of the windshield) can affect the probability of a pedestrian head strike in a particular area of the windshield. The bottom, left, and right edge areas of the windshield 20 can sometimes have difficulty in achieving desirable HIC values in safety testing in conventional laminates.

[0050] The fracture -initiation points themselves can be arranged in a dot pattern as shown in Figure 6, or in other arrangements as discussed herein. In a dot pattern of fracture- initiations points, such as shown in Figure 6, the dots can be spaced from about 3 inches to about 6 inches apart from each other. In some embodiments, the dots can be spaced apart by about 1 inch, about 2 inches, about 3 inches, about 4 inches, about 5 inches, about 6 inches, about 7 inches, about 8 inches, about 9 inches, about 10 inches, about 11 inches, or about 12 inches.

[0051] Figure 7 illustrates another embodiment in which fracture-initiation points are distributed on a windshield 24 in a grid pattern 26. The spacing of the lines in the grid 26 can be designed to increase the probability of breaking when the windshield 24 is impacted by a pedestrian’s head or a headform. For example, the horizontal spacing x and the vertical spacing y of the grid 26 can be sized so that an impact from a pedestrian or headform will trigger breakage of the windshield 24, whereas smaller impacts, such as from hail, stones, or other common impacts, will not trigger breakage of the windshield 24. In some embodiments, the horizontal spacing x and/or vertical spacing y may be about 250 mm. In addition, the horizontal and/or vertical spacing x and y may be from about 100 mm to about 600 mm, from about 100 mm to about 500 mm, from about 100 mm to about 400 mm, from about 100 mm to about 300 mm, from about 200 mm to about 600 mm, from about 200 mm to about 500 mm, from about 200 mm to about 400 mm, from about 300 mm to about 600 mm, from about 300 mm to about 500 mm, from about 300 mm to about 400 mm, from about 150 mm to about 350 mm, or about 250 mm. The grid 26 may extend over substantially the entire surface area of the windshield 24, as shown in Figure 7. However, in other embodiments, the grid or pattern may be confined to one or specific areas of a glass laminate or glazing. The lines in the grid pattern 26 are shown as being straight for simplicity, but individual lines of the pattern may be straight, entirely curved, or partially curved, for example.

[0052] Due to the small size of individual fracture-initiation points, the probability of a small object impacting a fracture-initiation point of the glass sheet is very small. But in the event that a small object does strike a fracture-initiation point, performance of the laminate where the fracture -initiation points are formed on a chemically strengthened glass ply can nonetheless be comparable to a conventional soda lime glass/soda lime glass laminate.

However, in the case of a large object impact (such as that from a head or headform), the high kinetic energy from the impact will cause failure of the closest fracture-initiation point(s), which will trigger breakage of the chemically-strengthened glass sheet and stretching of the interlayer, thus maximizing energy dissipation of the impact and increasing safety.

[0053] Figure 8 illustrates another embodiment where a windshield 28 has a pattern 30 of fracture -initiation points arranged in a number of circles 32. The circles 32 may be sized and arranged on the windshield 28 so that the windshield 28 preferentially breaks in response to an impact with a pedestrian head or a headform, while breakage is not triggered by certain other types of imapcts. For example, the size of the circles 32 may be large enough so that fracture is initiated from a stress field or hoop stress resulting from an impact with an object roughly the size and/or weight of a head, but not from an impact with smaller or lighter objects. The fracture -initiation points in the circles 32 may be oriented or aligned so that they will mainly react to a hoop stress in the glass laminate resulting from the predetermined type of impact. [0054] For example, the circles 32 can be designed so that breakage initiates within a certain time from the targeted impact (i.e., a pedestrian head or headform impact). In some embodiments, the time is less than or equal to about 5 milliseconds, less than or equal to about 4 milliseconds, less than or equal to about 3 milliseconds, less than or equal to about 2 milliseconds, or less than or equal to about 1 millisecond. By initiating breakage within a certain time, the risk of injury to a pedestrian can be decreased. In the embodiment of Figure 8, each circle 32 overlaps at least one other circle 32. However, embodiments are not limited to this particular arrange of circles 32. In particular, the pattern of fracture -initiation points can include points arranged in a variety of shapes, such as circles, ovals, rectangles, or lines collectively arranged in a number of patterns.

[0055] As discussed herein, laminates having at least one glass sheet of strengthened (e.g., chemically strengthened) glass that is relatively thin have advantages over conventional laminates with thicker plies. These advantages include weight savings. However, thinner laminates may be more prone to bend or deflect when impacted. For example, when an automotive glazing is impacted on its external surface (i.e., the surface facing the exterior of the vehicle), the glazing may bend or flex toward the interior of the vehicle. Thus, when a glazing or windshield receives an external impact (on surface 1 of the laminate), the maximum tension stresses in the inner glass sheet are located at surface 4. In addition, an external impact from a larger object, such as a head or headform, will place a large area of surface 4 in tension. In contrast, impacts from a small object, such as a stone, will put only a small area of surface 4 in tension. Thus, in view of the size of the area of surface 4 that is put into tension by a head or headform, the spacing or pattern of the fracture-initiation points of various embodiments discussed herein can be determined to optimize the breakage performance.

[0056] In some embodiments, the pattern is not extended to the edge of the glass sheet, so that unwanted edge failure is prevented or for other reasons. For example, the pattern may not extend to the top of a windshield, due to specifications related to the maximum Wrap Around Distance (or“WAD”) of a pedestrian or bicyclist in a vehicular collision, as specified by EURO-NCAP for a given vehicle and discussed in further detail below. For example, Figure 9 illustrates an embodiment of a windshield 34 similar to that of Figure 5, but the grid 36 does not extend to the top of the windshield 34. Instead, the grid 36 stops at line 38, which represents the maximum WAD location. The sizes of the squares in the grid can be modified to achieve the desired HIC value. In Figure 9, for example, the horizontal spacing x is 250 mm and the vertical spacing y is 250 mm for a given square of the grid. However, in various aspects of one or more embodiments, the horizontal and vertical spacing x and y can be from about 100 mm to about 600 mm, from about 100 mm to about 500 mm, from about 100 mm to about 400 mm, from about 100 mm to about 300 mm, from about 200 mm to about 600 mm, from about 200 mm to about 500 mm, from about 200 mm to about 400 mm, from about 300 mm to about 600 mm, from about 300 mm to about 500 mm, from about 300 mm to about 400 mm, or from about 150 mm to about 350 mm.

[0057] Figure 10 illustrates a windshield 40 according to an embodiment in which the pattern 42 is formed as a series of circles 44, some of which are concentric and/or overlapping. Again, the circles 44 do not extend all the way to the top of the windshield 40, and instead stop at a point 46, which may represent the maximum WAD location. According to the pattern shown in Figure 10, a laminate having an inner glass sheet of chemically strengthened glass can comply with ECE-R43 regulatory head impact test criteria, that requires a circular fracturing pattern in both glass plies, which may not be achieved in a chemically strengthened glass sheet without a pattern of fracture-initiation points (or un strengthened lines resulting from IOX -masking). As discussed above, the size of individual circles 44, the spacing between circles 44, and/or the amount of overlaps of circles 44 can be designed to preferential break in response to a head impact event, but not in response to other types of impact events.

[0058] As discussed above, fracture-initiation points can be formed via localized and controlled weakening of a glass sheet, including weakening by localized masking during the ion exchange process. In some embodiments using localized masking during ion exchange, the low-strength areas are formed on at least surface 4 of the laminate. However, the low- strength areas may also be formed on surface 3, or surface 3 and surface 4. Embodiments are not limited to any specific material or coating, but the coating should be able to sustain the ion exchange bath conditions to be effective, and be removed after the ion exchange. The coating used to retard ion exchange can be applied in a number of different patterns, including lines, squares, circles, or other shapes. The pattern can be applied using a line width of about 500 pm or less, about 400 pm or less, about 300 pm or less, about 200 pm or less, about 100 mih or less, or about 50 mih or less. In a particular embodiment, the line widths are about 100 mih or less.

[0059] In some embodiments, the line width is designed to be about twice that of the depth of layer (DOL). As shown in Figure 11, a line width of twice the DOL allows the surface compress stress (CS) to reach approximately zero near the center of the line at the surface of the glass sheet. Of course, the line width can be adjusted to achieve a desired CS. The tapered shape of the CS curve in Figure 11 can be a result of ion exchange occurring via diffusion near the edge of the line or mask on the surface of the glass. The line in Figure 11 can be considered to completely block direct IOX through the line. However, in some embodiments, it can be sufficient to merely slow IOX through the line, without completely blocking IOX through the line. In such a case, the CS would not be reduced to zero under the line, but it would still be possible to lower the CS and/or depth of compression (DOC) under the patterned regions relative to surrounding regions. Even two regions having similar CS can have different strengths if the subsurface stress profiles are different, such as in having different DOC, because the compressive stress at characteristic flaw depths will differ.

[0060] Due to the small line width of the coating, the probability of a small object impacting an un-strengthened area of the glass sheet is very small. But if a small object does strike the un-strengthened area, performance of the laminate in that area can nonetheless be comparable to a conventional soda lime glass/soda lime glass laminate. However, in the case of a large object impact (such as that from a head or headform), the high kinetic energy from the impact will cause failure of the closest un-strengthened line or area, which will trigger breakage of the chemically-strengthened glass sheet and stretching of the interlayer, thus maximizing energy dissipation of the impact and increasing safety.

[0061] As discussed above, the local un-strengthened achieved via masking during the ion exchange process can be performed on surface 4, or both surface 3 and surface 4. However, in some embodiments, it may be performed only on surface 4, so that surface 3 is fully strengthened during ion exchange. In this case, the laminate may have improved performance with respect to passenger and airbag protection during such impacts from the inside (impacts on surface 4), which put surface 3 in tension and surface 4 in compression.

[0062] According to embodiments of this disclosure, referring to Figure 1, the inner glass sheet 13 may be chemically strengthened glass having a thickness of 1.5 mm or less or 1.0 mm or less, for example 0.7 mm, 0.55 mm, or 0.5 mm, that has been strengthened via an ion exchange process. For example, the inner glass sheet 13 may both be formed of Coming^® Gorilla^® glass from Coming Incorporated. As described in U.S. Patent Nos. 7666511, 4483700 and 5674790, Coming Gorilla glass is made by fusion drawing a glass sheet and then chemical strengthening the glass sheet. As described in more detail hereinafter, Coming Gorilla glass has a relatively deep depth of layer (DOL) of compressive stress, and presents surfaces having a relatively high flexural strength, scratch resistance and impact resistance.

[0063] Terms of orientation, such as“outer,”“external”“internal” and“inner” are used in certain embodiments described herein in relation to the inside and outside of a vehicle, device or building, but it will be appreciated that the laminate could be reversed in certain application such that the inner and outer surfaces of the laminate are reversed. As such, these terms as used in the present disclosure and in the appended claims should be interpreted as orienting the layers in the laminate and the surfaces of the layers in relation to each other, rather than in relation the inside or outside of a vehicle, device or stmcture unless specifically stated otherwise.

[0064] According to certain embodiments hereof, the fracture-initiation points 17 formed in surface 3 or surface 4 of the inner glass sheet 13 are micron-level flaws created in surface 3 or 4 of the laminate (as shown, for example, in Figures 4 and 5). Because many applications require good optical properties, it may be advantageous that these flaws to be invisible to the human eye. The fracture -initiation points 17 that are invisible to the human eye may be created on surfaces 3 or 4 of the inner glass sheet using, by way of example only, a picosecond laser or a femtosecond laser. A picosecond laser is a laser with its optical pulse duration in the domain of picoseconds (1 ps = 10 ¹² s). A femtosecond laser is a laser which emits optical pulses with a duration well below 1 ps, i.e., in the domain of femtoseconds (1 fs = 10 ¹⁵ s). The fracture-initiation points 17 may be formed in surface 3 or surface 4 using other mechanical means, such as sandblasting or wheel abrading, but these methods may detrimentally affect the optical properties of the laminate 10 and may even create visual damage, which may be acceptable or even serve as a desirable ornamental feature in certain applications. In the case of surface 3, such visual damage may be effectively hidden by using a PVB interlayer 15 having an index or refraction that substantially matches the index of refraction of the inner glass sheet, or by applying a coating or film to the outer surface 3 of the inner glass sheet that has an index of refraction that substantially matches the index of refraction of the inner glass sheet. Similarly, for flaws formed in surface 4, a coating or film can be applied to surface 4 of the inner glass sheet 13, where the coating or film has an index of refraction that substantially matches the index of refraction of the inner glass sheet.

[0065] According to certain embodiments hereof, by way of example only, the inner glass sheet 13 is chemically strengthened to have a CS of about 700 MPa to about 750 MPa and a DOL of 40 pm, and the controlled flaws are formed in the third outer surface or the fourth inner surface of the inner glass sheet (i.e., surfaces 3 and 4 of the laminate, respectively). In some embodiments, the flaws may have a diameter or width of 20 pm, a depth of 45 +/- 4 pm and may be spaced apart from each other by a distance of about 2 mm to about 10 mm, or more.

[0066] In some embodiments, it may be disadvantageous for the controlled flaws to completely penetrate the DOL of the compressive stress layer formed in the chemical strengthening process, as this may weaken the glass sheet and the resulting laminate to an unacceptable degree. The controlled flaws may advantageously extend through large portion or majority of the DOL of the compressive stress layer. For example, the controlled flaws may extend about 20% or more, about 30% or more, about 40% or more, about 50% or more, about 60% or more, or about 70% or more, about 80% or more, about 90% or more, or in a range from about 80% to about 90% the depth of the DOL, through the DOL, but less than 100% through the DOL in the glass sheet. The size, shape, and frequency (spacing) of the flaws 17 will vary depending on the laminate constructions and desired performance of the laminate. For example, thicker glass sheets may require more (more closely spaced), deeper flaws than thinner glass sheets to obtain a desired breakage performance. In any event, the depth and width of the flaws should be small enough that the flaws are not visible. The depth of the flaws and flaw tip geometry impacts the performance of the flaws as weakening fracture initiation sites. The width and length are important around visibility, which is very dependent on geometry, how the flaw is created and how the flaw effects the transmitted and reflected light.

[0067] In an alternative embodiment of the present disclosure the flaws may be formed in the surface of the glass prior to ion exchange. In this case, the flaws may be formed to a depth as described above, or may me formed to depth that is up to two times to three times the DOL, e.g., the depth of the flaws may be about 150%, about 200%, about 250% or about 300% of the DOL.

[0068] According to certain embodiments hereof the desired strength/breakage performance of the laminate may be achieved or controlled by controlling how deep the flaws are formed in the glass. The flaws may be created on/in the surface of the glass sheet or internally in the glass sheet, i.e., leaving the glass surface of the sheet undamaged by the laser. For example, the strength of the laminate can be selected by controlling the depth of the controlled flaws in or below the surface 3 or 4.

[0069] As previously described, suitable glass sheets may be chemically strengthened by an ion exchange process. In this process, typically by immersion of the glass sheet into a molten salt bath for a predetermined period of time, ions within the glass sheet at or near the surface of the glass sheet are exchanged for larger metal ions, for example, from the salt bath. In one embodiment, the temperature of the molten salt bath is about 430°C and the predetermined time period is about eight hours. The incorporation of the larger ions into the glass strengthens the sheet by creating a compressive stress in a near surface region. A corresponding tensile stress is induced within a central region of the glass sheet to balance the compressive stress.

[0070] Example ion-exchangeable glasses that are suitable for forming glass laminates are alkali aluminosilicate glasses or alkali aluminoborosilicate glasses, though other glass compositions are contemplated. As used herein,“ion exchangeable” means that a glass is capable of exchanging cations located at or near the surface of the glass with cations of the same valence that are either larger or smaller in size.

[0071] One example glass composition comprises S1O2, B2O3 and Na20, where (S1O2 + B2O3) > 66 mol.%, and Na20 > 9 mol.%. In an embodiment, the glass sheets include at least 6 wt.% aluminum oxide. In a further embodiment, a glass sheet includes one or more alkaline earth oxides, such that a content of alkaline earth oxides is at least 5 wt.%. Suitable glass compositions, in some embodiments, further comprise at least one of K2O, MgO, and CaO. In a particular embodiment, the glass can comprise 61-75 mol.% S1O2; 7-15 mol.% AI2O3; 0-12 mol.% B2O3; 9-21 mol.% Na20; 0-4 mol.% K2O; 0-7 mol.% MgO; and 0-3 mol.% CaO.

[0072] A further example glass composition suitable for forming glass laminates comprises: 60-70 mol.% S1O2; 6-14 mol.% AI2O3; 0-15 mol.% B2O3; 0-15 mol.% L12O; 0-20 mol.% Na₂0; 0-10 mol.% K2O; 0-8 mol.% MgO; 0-10 mol.% CaO; 0-5 mol.% Zr0₂; 0-1 mol.% Sn02; 0-1 mol.% Ce02; less than 50 ppm AS2O3; and less than 50 ppm Sb203; where 12 mol.% < (L12O + Na20 + K2O) < 20 mol.% and 0 mol.% < (MgO + CaO) < 10 mol.%.

[0073] A still further example glass composition comprises: 63.5-66.5 mol.% S1O2; 8-12 mol.% AI2O3; 0-3 mol.% B2O3; 0-5 mol.% L12O; 8-18 mol.% Na₂0; 0-5 mol.% K2O; 1-7 mol.% MgO; 0-2.5 mol.% CaO; 0-3 mol.% Zr0₂; 0.05-0.25 mol.% Sn0₂; 0.05-0.5 mol.% Ce02; less than 50 ppm AS2O3; and less than 50 ppm Sb203; where 14 mol.% < (L12O + Na20 + K2O) < 18 mol.% and 2 mol.% < (MgO + CaO) < 7 mol.%.

[0074] In a particular embodiment, an alkali aluminosilicate glass comprises alumina, at least one alkali metal and, in some embodiments, greater than 50 mol.% S1O2, in other embodiments at least 58 mol.% S1O2, and in still other embodiments at least 60 mol.% S1O2,

Al₂0₃ + B₂0₃

wherein the ratio > 1 , wherein the ratio the components are expressed in mod ifiers

mol.% and the modifiers are selected from alkali metal oxides. This glass, in particular embodiments, comprises, consists essentially of, or consists of: 58-72 mol.% S1O2; 9-17 mol.% AI2O3; 2-12 mol.% B2O3; 8-16 mol.% Na20; and 0-4 mol.% K2O, wherein the ratio 0₃ + B₂0₃

> 1 .

mod ifiers

[0075] In another embodiment, an alkali aluminosilicate glass comprises, consists essentially of, or consists of: 61-75 mol.% SiCh; 7-15 mol.% AI2O3; 0-12 mol.% B2O3; 9-21 mol.% Na20; 0-4 mol.% K2O; 0-7 mol.% MgO; and 0-3 mol.% CaO.

[0076] In yet another embodiment, an alkali aluminosilicate glass substrate comprises, consists essentially of, or consists of: 60-70 mol.% S1O2; 6-14 mol.% AI2O3; 0-15 mol.% B2O3; 0-15 mol.% L12O; 0-20 mol.% Na₂0; 0-10 mol.% K2O; 0-8 mol.% MgO; 0-10 mol.% CaO; 0-5 mol.% Zr02; 0-1 mol.% Sn02; 0-1 mol.% Ce02; less than 50 ppm AS2O3; and less than 50 ppm Sb203; wherein 12 mol.% < L12O + Na20 + K2O < 20 mol.% and 0 mol.% < MgO + CaO < 10 mol.%.

[0077] In still another embodiment, an alkali aluminosilicate glass comprises, consists essentially of, or consists of: 64-68 mol.% S1O2; 12-16 mol.% Na20; 8-12 mol.% AI2O3; 0-3 mol.% B2O3; 2-5 mol.% K2O; 4-6 mol.% MgO; and 0-5 mol.% CaO, wherein: 66 mol.% <

S1O2 + B2O3 + CaO < 69 mol.%; Na20 + K2O + B2O3 + MgO + CaO + SrO > 10 mol.%; 5 mol.% < MgO + CaO + SrO < 8 mol.%; (Na20 + B2O3) - AI2O3 < 2 mol.%; 2 mol.% < Na20

- AI2O3 < 6 mol.%; and 4 mol.% < (Na20 + K2O) - AI2O3 < 10 mol.%.

[0078] The glass, in some embodiments, is batched with 0-2 mol.% of at least one fining agent selected from a group that includes Na2S0₄, NaCl, NaF, NaBr, K2SO4, KC1, KF, KBr, and SnC .

[0079] In one example embodiment, sodium ions in the glass can be replaced by potassium ions from the molten bath, though other alkali metal ions having a larger atomic radius, such as rubidium or cesium, can replace smaller alkali metal ions in the glass. According to particular embodiments, smaller alkali metal ions in the glass can be replaced by Ag⁺ ions. Similarly, other alkali metal salts such as, but not limited to, sulfates, halides, and the like may be used in the ion exchange process.

[0080] The replacement of smaller ions by larger ions at a temperature below that at which the glass network can relax produces a distribution of ions across the surface of the glass that results in a stress profile. The larger volume of the incoming ion produces a compressive stress (CS) on the surface and tension (central tension, or CT) in the center region of the glass. The compressive stress is related to the central tension by the following relationship:

where t is the total thickness of the glass sheet and DOL is the depth of exchange, also referred to as depth of layer.

[0081] According to various embodiments, thin glass laminates comprising one or more sheets of ion-exchanged glass and having a specified depth of layer versus compressive stress profile possess an array of desired properties, including low weight, high impact resistance, and improved sound attenuation.

[0082] In one embodiment, a chemically-strengthened glass sheet can have a surface compressive stress of at least 300 MPa, e.g., at least 400 MPa, at least 500 MPa, at least 600 MPa, at least 700 MPa, or from about 300 MPa to about 1000 MPa, a depth of compression (DOC) of at least about 20 pm (e.g., at least about 20, 25, 30, 35, 40, 45, 50, 55, 60, 65„70, 75, 80, 85, or 90 pm) and/or a central tension greater than 40 MPa (e.g., greater than 40, 45, or 50 MPa) and less than 100 MPa (e.g., less than 100, 95, 90, 85, 80, 75, 70, 65, 60, or 55

MPa). [0083] Independently of, or in conjunction with, the foregoing relationships, the chemically-strengthened glass can have depth of layer that is expressed in terms of the corresponding surface compressive stress. In one example, the near surface region extends from a surface of the glass sheet to a depth of layer (in micrometers) of at least

65-0.06(CS), where CS is the surface compressive stress and has a value of at least 300 MPa.

[0084] In a further example, the near surface region extends from a surface of the glass sheet to a depth of layer (in micrometers) having a value of at least B-M(CS), where CS is the surface compressive stress and is at least 300 MPa. In the foregoing expression, B can range from about 50 to 180 (e.g., 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160 ± 5), and M can range independently from about -0.2 to -0.02 (e.g., -0.18, -0.16, -0.14, -0.12, -0.10, -0.08, - 0.06, -0.04 ± -0.01).

[0085] A modulus of elasticity of a chemically-strengthened glass sheet can range from about 60 GPa to 85 GPa (e.g., 60, 65, 70, 75, 80 or 85 GPa). The modulus of elasticity of the glass sheet(s) and the polymer interlayer can affect both the mechanical properties (e.g., deflection and strength) and the acoustic performance (e.g., transmission loss) of the resulting glass laminate.

[0086] Glass laminates for automotive glazing and other applications can be formed using a variety of processes. In an example process, one or more sheets of chemically-strengthened glass sheets can be assembled in a pre-press with a polymer interlayer, tacked into a pre laminate, and finished into an optically clear glass laminate. A thermoplastic material such as PVB may be applied as a preformed polymer interlayer. The thermoplastic layer can, in certain embodiments, have a thickness of at least 0.125 mm (e.g., 0.125, 0.25, 0.375, 0.5,

0.75, 0.76 or 1 mm). The thermoplastic layer can cover most or, preferably, substantially all of the two opposed major faces of the glass. It may also cover the edge faces of the glass. The glass sheet(s) in contact with the thermoplastics layer may be heated above the softening point of the thermoplastic, such as, for example, at least 5°C or l0°C above the softening point, to promote bonding of the thermoplastic material to the glass. The heating can be performed with the glass ply in contact with the thermoplastic layers under pressure.

[0087] A modulus of elasticity of the polymer interlayer can range from about 1 MPa to 75 MPa (e.g., about 1, 2, 5, 10, 15, 20, 25, 50 or 75 MPa). At a loading rate of 1 Hz, a modulus of elasticity of a standard PVB interlayer can be about 15 MPa, and a modulus of elasticity of an acoustic grade PVB interlayer can be about 2 MPa.

[0088] One or more polymer interlayers may be incorporated into a glass laminate. A plurality of interlayers may provide complimentary or distinct functionality, including adhesion promotion, acoustic control, UV transmission control, and/or IR transmission control.

[0089] The glass laminates can be adapted for use, for example, as windows or glazings, and configured to any suitable size and dimension. In embodiments, the glass laminates have a length and width that independently vary from 10 cm to 1 m or more (e.g., 0.1, 0.2, 0.5, 1,

2, or 5 m). Independently, the glass laminates can have an area of greater than 0.1 m², e.g., greater than 0.1, 0.2, 0.5, 1, 2, 5, 10, or 25 m².

[0090] The glass laminates can be substantially flat or shaped for certain applications. For instance, the glass laminates can be formed as bent or shaped parts for use as windshields or cover plates. The structure of a shaped glass laminate may be simple or complex. In certain embodiments, a shaped glass laminate may have a complex curvature where the glass sheets have a distinct radius of curvature in two independent directions. Such shaped glass sheets may thus be characterized as having“cross curvature,” where the glass is curved along an axis that is parallel to a given dimension and also curved along an axis that is perpendicular to the same dimension. An automobile sunroof, for example, typically measures about 0.5 m by 1.0 m and has a radius of curvature of 2 to 2.5 m along the minor axis, and a radius of curvature of 4 to 5 m along the major axis.

[0091] Methods for bending and/or shaping glass laminates can include gravity bending, press bending and methods that are hybrids thereof. In a traditional method of gravity bending thin, flat sheets of glass into curved shapes such as automobile windshields, cold, pre-cut single or multiple glass sheets are placed onto the rigid, pre-shaped, peripheral support surface of a bending fixture. The bending fixture may be made using a metal or a refractory material. In an example method, an articulating bending fixture may be used. Prior to bending, the glass typically is supported only at a few contact points. The glass is heated, usually by exposure to elevated temperatures in a lehr, which softens the glass allowing gravity to sag or slump the glass into conformance with the peripheral support surface. Substantially the entire support surface generally will then be in contact with the periphery of the glass.

[0092] A related technique is press bending where flat glass sheets are heated to a temperature corresponding substantially to the softening point of the glass. The heated sheets are then pressed or shaped to a desired curvature between male and female mold members having complementary shaping surfaces. In embodiments, a combination of gravity bending and press bending techniques can be used.

[0093] Applicants have shown that the glass laminate structures disclosed herein have excellent durability, impact resistance, toughness, and scratch resistance, while having improved breakage performance with respect to pedestrian safety. Due to chemical strengthening, one or both of the external surfaces of the glass laminates disclosed herein are under compression. For flaws to propagate and failure to occur, the tensile stress from an impact must exceed the surface compressive stress at the tip of the flaw. In embodiments, the high compressive stress and high depth of layer of chemically-strengthened glass sheets enable the use of thinner glass than in the case of non-chemically-strengthened glass.

[0094] In an embodiment hereof, a glass laminate can comprise inner and/or outer glass sheets such as chemically-strengthened glass sheets. In particular, the inner-facing glass sheet (e.g., an inner chemically-strengthened glass sheet) can have a surface compressive stress of from one-third to one-half the surface compressive stress of the outer chemically- strengthened glass sheet, or equal that of the outer glass sheet. Flaws may optionally be formed in the outer surface 3 or inner surface 4 of the inner glass sheet.

[0095] In other embodiments hereof the outer glass sheet 11 maybe formed of a non- chemically strengthened glass sheet, such as a soda lime glass sheet, having a thickness of about 1.5 mm or greater, about 2 mm or greater or about 2.5 mm or greater and the inner glass sheet 13 may be a thin chemically strengthened glass sheet having a thickness, CS,

DOL and flaws formed in its external third surface as previously described herein. The CS of the inner glass sheet in these embodiments may be about 700 MPa or greater. The non- chemically strengthened external glass sheets may optionally be heat strengthened or thermally tempered. Alternatively, the outer third surface of the inner glass sheet in these embodiments may be free of flaws and the CS may be about 300 MPa or greater. [0096] In further embodiments hereof, the the inner sheet 13 maybe formed of non- chemically strengthened glass sheet, such as a soda lime glass sheet, having a thickness of about 1.5 mm or greater, about 2 mm or greater, or about 2.5 mm or greater and the outer glass sheet 11 may be a thin chemically strengthened glass sheet having a thickness, CS and DOL as previously described herein. In the case of an outer glass sheet 11 that is chemically strengthened, the flaws discussed herein may be formed on one or both of surface 1 and surface 2. The CS of the inner glass sheet in these embodiments may be about 550 MPa. The non-chemically strengthened internal glass sheet may optionally be heat strengthened or thermally tempered and may optionally have flaws as previously described herein formed in its outer third surface.

[0097] Pedestrian Protection Criteria

[0098] Certain aspects of pedestrian protection testing and rating will be discussed below to inform the mechanical performance and advantages of embodiments of this disclosure. References herein to the EURO-NCAP protocol are to the EURO-NCAP Assessment Protocol v9.0.2, the EURO-NCAP Pedestrian Test Protocol v8.4, and the EURO-NCAP Autonomous Emergency Breaking (AEF) Vulnerable Road User (VRU) Test Protocol v2.0.2. While the EURO-NCAP protocols involve impact testing using headform, upper legform, and lower legform testing, as well as AEB test data, and include impacts to the bumper and bonnet/hood of vehicles, embodiments of this disclosure are primarily concerned with impacts to the glazing or windshield.

[0099] According to the EURO-NCAP safety ratings system, the potential risk of head injury in the event of a vehicle striking a pedestrian is estimated using a series of impact tests is performed using a headform impactor traveling at up to 40 km/h. The tests include impacting the headform at several grid points on the bonnet/hood and on an installed windshield. In the headform impact area, a grid of points 54 is marked on the outer surface of the vehicle 50, including on the windshield 52, as shown in Figure 12, and some or all of the points are tested. The headform test area is bounded by the geometric trace of the 1000 mm wrap around line 56 in the front, the sides 60 and 62 of the bonnet/hood, and the 2100 mm wrap around distance (WAD) 58, as shown in Figures 13 and 14.

[00100] The impact points are then assessed and the protection offered is rated as“good,” “adequate,”“marginal,”“weak,” or“poor.” Specifically, each point of the grid points can be awarded up to one scoring point according to the measured Head Injury Criterion (HIC) value (HIC < 650 = 1.00 point; 650 < HIC < 1000 = 0.75 points; 1000 < HIC < 1350 = 0.50 points; 1350 < HIC < 1700 = 0.25 points; and 1700 < HIC = 0.00 points). The final score will define the number of safety stars that the vehicle will be granted (from 1 to 5). The data can be represented by color-coding the grid points according to the color codes shown in Table 1 below. EURO-NCAP rates each and every model of vehicle with its own test. The following Equation 1 is used to calculate HIC:

Equation 1.

Table 1. HIC Vale Color Coding.

[00101] The vehicle manufacturer provides HIC values (or color data according to Table 1) to the EURO-NCAP testing facility detailing the predicted protection offered by the vehicle, and EURO-NCAP tests a random collection of those provided points. The actual protection or HIC values are then compared to the predicted values. Some of the grid points are defaulted to a green or red rating. For example, points on the windshield glazing may be defaulted to green except for (1) any grid points that are within 165 mm of the solid strip around the periphery of the windshield mounting frame, where the 165 mm is measured along the outer contour of the windshield, as shown in Figure 15; (2) any areas where there are structures mounted directly behind the windshield, such as sensor systems; and (3) grid points on the windshield that are within 100 mm of any underlying structures in the windshield base area, measured from the grid point in the impact direction of the relevant headform.

[00102] As shown in Figure 16, when impacting with the headform 64, a selected grid point 66 is treated as the aiming point for the headform 64, where the centerline 68 of the headform 64 is in the line of flight of the headform 64 toward the aiming point 66. The headform conforms to Regulation (EC) 78/2009 of the European Parliament and of the Council (l4^th January 2009) and annexed in Regulation (EC) 631/2009 (22^nd July 2009). Further details of the testing procedures and requirements can be found in the above-referenced EURO-NCAP protocols.

[00103] The Testing can also be performed with the headform travelling at less than 40 km/h, with a sliding scale used to adjust the score for lower velocity impacts. Test speeds higher than 40 km/h can also be assessed on a pass/fail basis.

[00104] Example

[00105] HIC values were measured for four laminates according to some embodiments of this disclosure. Each laminate was made with an outer ply of unstrengthened soda-lime glass (SLG), an inner ply of chemically strengthened Gorilla® Glass (GG), and various interlays having at least one of standard polyvinyl butyral (PVB) or acoustic PVB. Further details of the laminate constructions are provided below in Table 2. The plies of Gorilla® Glass had a compressive stress (CS) of about 694 MPa, and depth of layer (DOL) of compression of about 46 pm.

Table 2. HIC Values for Samples 1-4.

[00106] Each of Samples 1-4 were tested according to standard HIC value testing as described above. Strain gauges were used to measure the maximum stress on the inner ply opposite to the point of impact. The strain gauges were applied using a high-modulus adhesive, which can function as a fracture-initiation coating as described above. For Sample 1, both plies fractured with no tearing of the PVB interlayer and the maximum stress measured by the gauge was about 400 MPa. For Sample 2, both plies fractured with no tearing of the PVB interlayer and the maximum stress measured was about 650 MPa. For Sample 3, both plies broke with no tearing of the PVB interlayer and the maximum stress measured was about 540 MPa. For sample 4, both plies broke, and the maximum stress measured was about 350 MPa. As shown in Table 2, the HIC values ranged from 176 to 381, which means all would qualify for the“green” color code.

[00107] According to an aspect (1) of the present disclosure, a glass laminate is provided. The glass laminate comprising: an outer glass sheet having a first outer surface and a second inner surface; an inner glass sheet having a third outer surface and a fourth inner surface; and a polymer interlayer between the outer glass sheet and the inner glass sheet, wherein at least one of the inner glass sheet and the outer glass sheet has a thickness of about 2 mm or less, and wherein at least one of the inner glass sheet and the outer glass sheet comprises a plurality of fracture-initiation points in a predetermined pattern, the predetermined pattern being configured to weaken the glass laminate in the event of a predetermined external impact on the first outer surface.

[00108] According to an aspect (2) of the present disclosure, the glass laminate of aspect (1) is provided, wherein the fracture-initiation points comprise at least one of the following: flaws or defects within at least one of the inner glass sheet and the outer glass sheet; or flaws or defects on at least one of the first outer surface, the second inner surface, the third outer surface, or the fourth inner surface.

[00109] According to an aspect (3) of the present disclosure, the glass laminate of aspect (2) is provided, wherein the flaw or defects comprise at least one of a coating, a particle, a surface imperfection, a locally annealed region, a locally laser-ablated region, or a locally weakened area on at least one of the first outer surface, the second inner surface, the third outer surface, or the fourth inner surface.

[00110] According to an aspect (4) of the present disclosure, the glass laminate of any of aspects (l)-(3) is provided, wherein the predetermined external impact is a pedestrian head or headform impact. [00111] According to an aspect (5) of the present disclosure, the glass laminate of any of aspects (l)-(4) is provided, wherein the at least one of the inner glass sheet and the outer glass sheet is chemically strengthened.

[00112] According to an aspect (6) of the present disclosure, the glass laminate of aspect (5) is provided, wherein the inner glass sheet has a thickness of 2 mm or less and is chemically strengthened.

[00113] According to an aspect (7) of the present disclosure, the glass laminate of any of aspects (l)-(6) is provided, wherein the outer glass has a thickness of about 1.5 mm or greater and is not chemically strengthened.

[00114] According to an aspect (8) of the present disclosure, the glass laminate of aspect (7) is provided, wherein the outer glass sheet comprises soda lime glass.

[00115] According to an aspect (9) of the present disclosure, the glass laminate of any of aspects (l)-(8) is provided, wherein the fracture-initiation points are formed in substantially the entire area of at least one of the third outer surface and the fourth inner surface.

[00116] According to an aspect (10) of the present disclosure, the glass laminate of any of aspects (l)-(9) is provided, wherein the glass laminate is a vehicle glazing or windshield.

[00117] According to an aspect (11) of the present disclosure, the glass laminate of any of aspects (1)-(10) is provided, wherein the fracture-initiation points are formed in at least one select region of the third outer surface or the fourth inner surface.

[00118] According to an aspect (12) of the present disclosure, the glass laminate of aspect (10) is provided, wherein the glass laminate is a windshield having a bottom side that is nearest to a hood of a vehicle when installed in the vehicle, a top side nearest the roof of the vehicle, and lateral sides connecting the top and bottom sides, wherein the fracture-initiation points are formed only in one or more regions within a predetermined distance from the bottom side or each of the lateral sides of at least one of the third outer surface and the fourth inner surface.

[00119] According to an aspect (13) of the present disclosure, the glass laminate of aspect (12) is provided, wherein the predetermined distance is 165 mm or less.

[00120] According to an aspect (14) of the present disclosure, the glass laminate of any of aspects (l)-(l 1) is provided, wherein the fracture-initiation points are arranged in lines forming a grid pattern extending over a surface area of the glass laminate. [00121] According to an aspect (15) of the present disclosure, the glass laminate of aspect (14) is provided, wherein a distance between consecutive lines in the grid pattern is from about 100 mm to about 500 mm, or from about 200 mm to about 300 mm, or about 250 mm.

[00122] According to an aspect (16) of the present disclosure, the glass laminate of any of aspects (14)-(15) is provided, wherein a distance between consecutive lines in the grid pattern is less than or equal to a diameter or a width of an area of tension created in the third outer surface or the fourth inner surface by an impact on the first surface from a pedestrian’s head or a headform, and is greater than a diameter or a width of an area of tension created in the third outer surface or the fourth inner surface by an impact on the first surface from an object other than a pedestrian’s head or a headform.

[00123] According to an aspect (17) of the present disclosure, the glass laminate of any of aspects (l)-(l 1) is provided, wherein the fracture-initiation points are arranged in one or more circles over a surface area of the glass laminate.

[00124] According to an aspect (18) of the present disclosure, the glass laminate of aspect (17) is provided, wherein a surface area of one of more of the circles is larger than an area of tension in the third outer surface of the fourth inner surface resulting from an impact on the first surface from an object other than a pedestrian’s head or a headform.

[00125] According to an aspect (19) of the present disclosure, the glass laminate of any of aspects (16)-(18) is provided, wherein the object is one or more of the following: a stone, hail, or roadside debris.

[00126] According to an aspect (20) of the present disclosure, the glass laminate of any of aspects (16)-(18) is provided, wherein the object is smaller or lighter than a pedestrian’s head or a headform used for measuring head impact criteria (HIC) values.

[00127] According to an aspect (21) of the present disclosure, the glass laminate of any of aspects (l)-(20) is provided, wherein the inner glass sheet has a thickness not exceeding 1.5 mm, not exceeding 1.0 mm, or not exceeding 0.7 mm.

[00128] According to an aspect (22) of the present disclosure, the glass laminate of any of aspects (l)-(2l) is provided, wherein the inner glass sheet is chemically strengthened with a depth of layer (DOL) of about 40 pm. [00129] According to an aspect (23) of the present disclosure, the glass laminate of any of aspects (l)-(22) is provided, wherein the inner glass sheet is chemically strengthened to a surface compressive stress (CS) of at least 300 MPa, or at least 500 MPa.

[00130] According to an aspect (24) of the present disclosure, the glass laminate of any of aspects (l)-(23) is provided, wherein the fracture-initiation points comprise localized areas of lower surface compressive stress or lower depth of layer of compressive stress.

[00131] According to an aspect (25) of the present disclosure, the glass laminate of aspect

(24) is provided, wherein the localized areas are formed during a chemical strengthening process of the inner glass sheet.

[00132] According to an aspect (26) of the present disclosure, the glass laminate of aspect

(25) is provided, wherein the localized areas are formed by masking one or more portions of the third outer surface or the fourth inner surface of the inner glass sheet during an ion exchange process.

[00133] According to an aspect (27) of the present disclosure, the glass laminate of any of aspects (l)-(26) is provided, wherein the glass laminate is optimized to break in response to an impact on the first outer surface with a pedestrian’s head or a headform, wherein breakage is optimized by controlling at least one of a size, a spacing, a shape, a depth, or a location of the fracture -initiation points on or in the inner glass sheet.

[00134] According to an aspect (28) of the present disclosure, the glass laminate of any of aspects (l)-(27) is provided, wherein the fracture-initiation points are arranged so that fracture of the glass laminate is initiated within a time of about 3 ms from a predetermined impact on the first surface.

[00135] According to an aspect (29) of the present disclosure, the glass laminate of aspect (28) is provided, wherein the time is within about 2 ms.

[00136] According to an aspect (30) of the present disclosure, the glass laminate of any of aspects (l)-(29) is provided, wherein a shape of at least one of the fracture-initiation points is a line.

[00137] According to an aspect (31) of the present disclosure, the glass laminate of any of aspects (l)-(30) is provided, wherein the fracture-initiation points comprise a high-modulus coating. [00138] According to an aspect (32) of the present disclosure, the glass laminate of aspect (31) is provided, wherein the modulus of the high-modulus coating is greater than a modulus of the inner glass sheet.

[00139] According to an aspect (33) of the present disclosure, the glass laminate of any of aspects (l)-(32) is provided, wherein the fracture-initiation points comprise a plurality of flaws or defects separated from each other by about 3 inches to about 6 inches.

[00140] According to an aspect (34) of the present disclosure, the glass laminate of any of aspects (l)-(33) is provided, wherein the fracture-initiation points are arranged to initiate fracture of the glass laminate in response to a hoop stress of a predetermined magnitude on the third outer surface or the fourth inner surface.

[00141] According to an aspect (35) of the present disclosure, the glass laminate of aspect (26) is provided, wherein a line width of the mask is about 500 pm or less, about 400 pm or less, about 300 pm or less, about 200 pm or less, about 100 pm or less, or about 50 pm or less.

[00142] According to an aspect (36) of the present disclosure, the glass laminate of any of aspects (26) or (35) is provided, wherein the line width is about twice a desired depth of layer (DOL) of compressive stress of areas of the inner glass sheet to be strengthened.

[00143] According to an aspect (37) of the present disclosure, a vehicle is provided comprising the glass laminate of any of aspects (l)-(36).

[00144] According to an aspect (38) of the present disclosure, the vehicle of aspect (37) is provided, wherein the glass laminate is a windshield.

[00145] According to an aspect (39) of the present disclosure, the vehicle of aspect (38) is provided, wherein the windshield achieves a Head Impact Criteria (HIC) value of less than 650, less than 550, or less than 550.

[00146] According to an aspect (40) of the present disclosure, the vehicle of aspect (39) is provided, wherein the windshield achieves the HIC value for all points tested on the windshield.

[00147] According to an aspect (41) of the present disclosure, a method of producing a glass laminate having optimized breakage for improved pedestrian safety is provided. The method comprising: providing a first glass sheet and a second glass sheeting; laminating the first and second glass sheets together with a polymer interlayer therebetween to form a glass laminate, wherein the first glass sheet is an outer glass sheet of the glass laminate and comprises a first outer surface and a second inner surface, and the second glass sheet is an inner glass sheet of the resulting glass laminate and comprises a third outer surface and a fourth inner surface; and creating one or more fracture-initiation points on at least one of the third outer surface and the fourth inner surface, wherein the fracture-initiation points are arranged to cause fracture of the glass laminate in response to a predetermined impact on the first outer surface.

[00148] According to an aspect (42) of the present disclosure, the method of aspect (41) is provided, wherein the predetermined impact is an impact between a pedestrian’s head or a headform and the first outer surface.

[00149] According to an aspect (43) of the present disclosure, the method of any of aspects (4l)-(42) is provided, wherein the second glass sheet is chemically strengthened.

[00150] According to an aspect (44) of the present disclosure, the method of any of aspects (4l)-(43) is provided, wherein creating the one or more fracture-initiation points comprises at least one of the following: applying a coating to the third outer surface or the fourth inner surface, forming a surface imperfection in the third outer surface or the fourth inner surface, locally annealing a region of the second glass sheet, and locally weakening a region of the third outer surface or the fourth inner surface.

[00151] According to an aspect (45) of the present disclosure, the method of aspect (44) is provided, wherein the coating has a modulus of elasticity that is higher than a modulus of elasticity of the second glass sheet.

[00152] According to an aspect (46) of the present disclosure, the method of aspect (44) is provided, wherein locally weakening the region comprises masking the region during an ion- exchange step of chemically strengthening the second glass sheet.

[00153] As used herein, the singular forms“a,”“an,” and“the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a“metal” includes examples having two or more such“metals” unless the context clearly indicates otherwise.

[00154] Ranges can be expressed herein as from“about” one particular value, and/or to “about” another particular value. When such a range is expressed, examples include from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent“about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[00155] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order.

Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that any particular order be inferred.

[00156] It is also noted that recitations herein refer to a component of the present invention being“configured” or“adapted to” function in a particular way. In this respect, such a component is“configured” or“adapted to” embody a particular property, or function in a particular manner, where such recitations are structural recitations as opposed to recitations of intended use. More specifically, the references herein to the manner in which a component is“configured” or“adapted to” denotes an existing physical condition of the component and, as such, is to be taken as a definite recitation of the structural characteristics of the component.

[00157] It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Since modifications combinations, sub-combinations and variations of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A glass laminate comprising:

an outer glass sheet having a first outer surface and a second inner surface;

an inner glass sheet having a third outer surface and a fourth inner surface; and a polymer interlayer between the outer glass sheet and the inner glass sheet, wherein at least one of the inner glass sheet and the outer glass sheet has a thickness of about 2 mm or less, and

wherein at least one of the inner glass sheet and the outer glass sheet comprises a plurality of fracture-initiation points in a predetermined pattern, the predetermined pattern being configured to weaken the glass laminate in the event of a predetermined external impact on the first outer surface.

2. The glass laminate of claim 1, wherein the fracture-initiation points comprise at least one of the following:

flaws or defects within at least one of the inner glass sheet and the outer glass sheet; or

flaws or defects on at least one of the first outer surface, the second inner surface, the third outer surface, or the fourth inner surface.

3. The glass laminate of claim 2, wherein the flaw or defects comprise at least one of a coating, a particle, a surface imperfection, a locally annealed region, a locally laser-ablated region, or a locally weakened area on at least one of the first outer surface, the second inner surface, the third outer surface, or the fourth inner surface.

4. The glass laminate of any one of claims 1-3, wherein the predetermined external impact is a pedestrian head or headform impact.

5. The glass laminate of any one of claims 1-4, wherein the at least one of the inner glass sheet and the outer glass sheet is chemically strengthened.

6. The glass laminate of claim 5, wherein the inner glass sheet has a thickness of 2 mm or less and is chemically strengthened.

7. The glass laminate of any one of claims 1-6, wherein the outer glass has a thickness of about 1.5 mm or greater and is not chemically strengthened.

8. The glass laminate of claim 7, wherein the outer glass sheet comprises soda lime glass.

9. The glass laminate of any one of claims 1-8, wherein the fracture-initiation points are formed in substantially the entire area of at least one of the third outer surface and the fourth inner surface.

10. The glass laminate of any one of claims 1-9, wherein the glass laminate is a vehicle glazing or windshield.

11. The glass laminate of any one of the preceding claims, wherein the fracture-initiation points are formed in at least one select region of the third outer surface or the fourth inner surface.

12. The glass laminate of claim 10, wherein the glass laminate is a windshield having a bottom side that is nearest to a hood of a vehicle when installed in the vehicle, a top side nearest the roof of the vehicle, and lateral sides connecting the top and bottom sides,

wherein the fracture-initiation points are formed only in one or more regions within a predetermined distance from the bottom side or each of the lateral sides of at least one of the third outer surface and the fourth inner surface.

13. The glass laminate of claim 12, wherein the predetermined distance is 165 mm or less.

14. The glass laminate of any one of claims 1-11, wherein the fracture-initiation points are arranged in lines forming a grid pattern extending over a surface area of the glass laminate.

15. The glass laminate of claim 14, wherein a distance between consecutive lines in the grid pattern is from about 100 mm to about 500 mm, or from about 200 mm to about 300 mm, or about 250 mm.

16. The glass laminate of claim 14 or claim 15, wherein a distance between consecutive lines in the grid pattern is less than or equal to a diameter or a width of an area of tension created in the third outer surface or the fourth inner surface by an impact on the first surface from a pedestrian’s head or a headform, and is greater than a diameter or a width of an area of tension created in the third outer surface or the fourth inner surface by an impact on the first surface from an object other than a pedestrian’s head or a headform.

17. The glass laminate of any one of claims 1-11, wherein the fracture-initiation points are arranged in one or more circles over a surface area of the glass laminate.

18. The glass laminate of claim 17, wherein a surface area of one of more of the circles is larger than an area of tension in the third outer surface of the fourth inner surface resulting from an impact on the first surface from an object other than a pedestrian’s head or a headform.

19. The glass laminate of claim 16 or claim 18, wherein the object is one or more of the following: a stone, hail, or roadside debris.

20. The glass laminate of claim 16 or claim 18, wherein the object is smaller or lighter than a pedestrian’s head or a headform used for measuring head impact criteria (HIC) values.

21. The glass laminate of any one of the preceding claims, wherein the inner glass sheet has a thickness not exceeding 1.5 mm, not exceeding 1.0 mm, or not exceeding 0.7 mm.

22. The glass laminate of any one of the preceding claims, wherein the inner glass sheet is chemically strengthened with a depth of layer (DOL) of about 40 pm.

23. The glass laminate of any one of the preceding claims, wherein the inner glass sheet is chemically strengthened to a surface compressive stress (CS) of at least 300 MPa, or at least 500 MPa.

24. The glass laminate of any one of the preceding claims, wherein the fracture-initiation points comprise localized areas of lower surface compressive stress or lower depth of layer of compressive stress.

25. The glass laminate of claim 24, wherein the localized areas are formed during a chemical strengthening process of the inner glass sheet.

26. The glass laminate of claim 25, wherein the localized areas are formed by masking one or more portions of the third outer surface or the fourth inner surface of the inner glass sheet during an ion exchange process.

27. The glass laminate of any one of the preceding claims, wherein the glass laminate is optimized to break in response to an impact on the first outer surface with a pedestrian’s head or a headform, wherein breakage is optimized by controlling at least one of a size, a spacing, a shape, a depth, or a location of the fracture-initiation points on or in the inner glass sheet.

28. The glass laminate of any one of the preceding claims, wherein the fracture -initiation points are arranged so that fracture of the glass laminate is initiated within a time of about 3 ms from a predetermined impact on the first surface.

29. The glass laminate of claim 28, wherein the time is within about 2 ms.

30. The glass laminate of any one of the preceding claims, wherein a shape of at least one of the fracture -initiation points is a line.

31. The glass laminate of any one of the preceding claims, wherein the fracture-initiation points comprise a high-modulus coating.

32. The glass laminate of claim 31, wherein the modulus of the high-modulus coating is greater than a modulus of the inner glass sheet.

33. The glass laminate of any one of the preceding claims, wherein the fracture-initiation points comprise a plurality of flaws or defects separated from each other by about 3 inches to about 6 inches.

34. The glass laminate of any one of the preceding claims, wherein the fracture-initiation points are arranged to initiate fracture of the glass laminate in response to a hoop stress of a predetermined magnitude on the third outer surface or the fourth inner surface.

35. The glass laminate of claim 26, wherein a line width of the mask is about 500 pm or less, about 400 pm or less, about 300 pm or less, about 200 pm or less, about 100 pm or less, or about 50 pm or less.

36. The glass laminate of claim 35 or claim 26, wherein the line width is about twice a desired depth of layer (DOL) of compressive stress of areas of the inner glass sheet to be strengthened.

37. A vehicle comprising the glass laminate of any one of the preceding claims.

38. The vehicle of claim 37, wherein the glass laminate is a windshield.

39. The vehicle of claim 38, wherein the windshield achieves a Head Impact Criteria

(HIC) value of less than 650, less than 550, or less than 550.

40. The vehicle of claim 39, wherein the windshield achieves the HIC value for all points tested on the windshield.

41. A method of producing a glass laminate having optimized breakage for improved pedestrian safety, the method comprising:

providing a first glass sheet and a second glass sheeting;

laminating the first and second glass sheets together with a polymer interlayer therebetween to form a glass laminate,

wherein the first glass sheet is an outer glass sheet of the glass laminate and comprises a first outer surface and a second inner surface, and the second glass sheet is an inner glass sheet of the resulting glass laminate and comprises a third outer surface and a fourth inner surface; and

creating one or more fracture-initiation points on at least one of the third outer surface and the fourth inner surface,

wherein the fracture-initiation points are arranged to cause fracture of the glass laminate in response to a predetermined impact on the first outer surface.

42. The method of claim 41, wherein the predetermined impact is an impact between a pedestrian’s head or a headform and the first outer surface.

43. The method of claim 41 or claim 42, wherein the second glass sheet is chemically strengthened.

44. The method of any one of claims 41-43, wherein creating the one or more fracture- initiation points comprises at least one of the following:

applying a coating to the third outer surface or the fourth inner surface,

forming a surface imperfection in the third outer surface or the fourth inner surface, locally annealing a region of the second glass sheet, and

locally weakening a region of the third outer surface or the fourth inner surface.

45. The method of claim 44, wherein the coating has a modulus of elasticity that is higher than a modulus of elasticity of the second glass sheet.

46. The method of claim 44, wherein locally weakening the region comprises masking the region during an ion-exchange step of chemically strengthening the second glass sheet.