Field of the invention

The present disclosed invention relates to an armored window with improved ballistic resistance, and more particularly to an armored laminate with lateral confinement.

Background of the invention

Armor systems are used to prevent the penetration of projectiles into a protected area by providing panels made of a material with acceptable weight, volume and cost. There are three prevalent passive armor materials in use: metals, ceramics and glazing materials; each of them having certain advantages and limitations. While metal panels are preferred in applications where weight is not a vital concern, the ceramic panels have long been considered as an alternative due to their hardness and lightweight. However, the use of ceramic materials in armor has been limited mainly by cost, limited capability to withstand multiple hits and reparability issues after projectile hit. Ceramics are extremely hard, but brittle.

In an armor system, there is a glazing when a visible zone is required. A Ballistic Resistant Glazing (BRG) laminates make use of combinations of various types of glass and plastics to absorb and dissipate the energy of the projectile, prevent penetration and protect the occupants of the vehicle from the projectile and any spalling of the glass/projectile fragments. In a BRG laminate, glass layers, if used, may comprise various glass compositions such as borosilicate and aluminosilicate, in addition to soda- lime, as well as glass that has been thermally or chemically strengthened. Plastic non bonding layers comprising polyurethane, acrylic and polycarbonate are also sometimes used.

Ceramics as well as glazing materials have flaws and other macroscopic defects on their surfaces due mainly to its manufacture process. These defects play an important role when this type of material is under stress, making it highly vulnerable. Therefore, these materials fails before its atomic boundaries break up. It is the main reason that explains the brittleness behavior of ceramics and glazing materials.

In order to overcome the aforementioned limitations of ceramics, some research has proposed composite armors. For example, U.S. Pat. No. 6,532,857 discloses a ceramic array armor confined with shock isolated ceramic tiles with rubber between the tiles and over the top of them, so that cracks cannot propagate from one title to another due to the lower impedance of the rubber with respect to the ceramic. Another example is the patent application U.S. No. 2015/0369568 which discloses a lightweight composite armor encapsulated in fiber reinforced cementitious composite for pre-stressing the armor, so that this confinement absorbs and limits the transfer of impact energy from a ballistic threat, such a kinetic energy projectile.

However, these solutions cannot be implemented in an armored window because the major surfaces of a window cannot be surrounded by a confinement. Also, a laminated glazing makes use of combinations of various types of glass and plastics, so that the pre stressing cannot be applied on a uniform basis.

It would be advantageous to be able to increase the ballistic resistance of an armored window without increasing either the number of layers or the thickness of the window.

Summary of the invention

It is an object of the present invention to provide a pre-stressed armored window in order to improve the ballistic resistance of said window.

This object can be attained by an armored window with lateral confinement comprising an armored laminate having two major opposite surfaces and lateral sides; a plurality of main plates surrounding at least partially the lateral sides of the armored laminate; an outer frame disposed parallel to said plurality of main plates, so that said plurality of main plates are located between the outer frame and the lateral sides of the armored laminate; and pressing means mounted on the outer frame for pressing said plurality of main plates against the armored laminate, pre-stressing the armored laminate.

As can be noted, this invention allows the reduction of macroscopic flaws that exists in the glazing surface by exerting pressure through the confinement. Once the reduction has been achieved, some mechanical properties of the glazing improves, especially, the compressive strength. It is a fact that the ballistic performance is linked to the mechanical properties of the armored window, so that as long as the mechanical properties improves, the ballistic performance improves as well.

In addition, it must be noted that the invention results in superior ballistic resistance of the armored window with no increase in the laminate weight.

Brief description of the drawings

These features and advantages of the present invention will become apparent from the detailed description of the following embodiments in conjunction with the accompanying drawings, wherein:

FIG. 1 shows an exploded view of an armored window with lateral confinement according to a first embodiment of the present invention.

FIG.2 shows a cross sectional view A- A’ of the armored window with lateral confinement depicted in FIG. 1.

FIG.3 shows a cross sectional view of an armored window with lateral confinement according to a second embodiment of the present invention.

FIG. 4 shows a cross sectional view of an armored window with lateral confinement according to a third embodiment of the present invention.

Detailed description of the invention

Referring now to the drawings, there are shown preferred embodiments of the vehicle glazing according to the present invention.

FIGS. 1 and 2 show an armored window with lateral confinement 2 comprising an armored laminate 1, or ballistic composite, having two major opposite surfaces and lateral sides, four main plates 5 surrounding the lateral sides of the armored laminate, and an outer frame 7 disposed parallel to said plurality of main plates 5, so that the main plates 5 are located between the outer frame 7 and the lateral sides of the armored laminate 1. Additionally, for each plate 5, an intermediate layer 4 is provided between that plate 5 and the corresponding lateral side of the armored laminate 1 in order to maximize contact surface area and to avoid contact between the material of the main plate and the glass (e.g. metal-glass contact). Likewise, four filling layers 6 are provided, each filing layer 6 is disposed between the outer frame 7 and the corresponding main plate 5 in order to reduce wave propagation energy in the armored window. Both intermediate layers 4 and filing layers 6 provides an effectively acoustic impedance match between window and frame, transmitting the shock wave to the frame and reducing the laminate damage.

It must be noted that the outer frame 7 is a single structure, i.e. it is a frame. In Figure 1, it is divided for illustrative purposes only. In addition, it must be noted that both intermediate layers 4 and filing layers 6 are optional components to improve results.

Furthermore, the armored window comprises pressing means, such as screws 8 and clamping nut 9, which is mounted on the outer frame for pressing the main plates 5 against the armored laminate 1, pre-stressing said armored laminate 1.

An example of this first embodiment is an armored laminate 1 comprising: 5 mm borosilicate glass 21; 0.3 mm polyurethane (PU) 20; 10 mm aluminosilicate glass 19; 0.3 mm polyurethane 28; 10 mm soda-lime glass 16; 0.3 mm polyurethane 15; 10 mm soda-lime glass 14; 0.3 mm polyurethane 13; 10 mm soda-lime glass 12; 1.2 mm polyurethane 11; 3 mm polycarbonate 10. While the lateral confinement 2 comprises: silicon intermediate layers 4; armored steel main plates 5; acoustic matching cement filling layers 6 and armored steel frame 7.

FIG. 3 shows an armored window with lateral confinement 32 which comprises main plates 35, filling layers 36, intermediate layers 34, an outer frame 37 and pressing means 38, 39; but in this embodiment the intermediate layers 34, the main plates 35 and the filling layers 36 are distributed along the lateral sides of the armored laminate 31 in order to apply a different pre-stress between layers or groups of layers. As can be seen, in this embodiment, only top layers 49, 50, 51 and the bottom layer 40 are pre-stressed.

An example of this second embodiment is an armored laminate 31 comprising: 8mm aluminosilicate glass 51; 0.6 mm Polyvinyl butyral (PVB) 50; 12 mm chemically strengthened soda-lime glass 49; 0.6 mm PVB 48; 12 mm chemically strengthened soda-lime glass 46; 0.6 mm PVB 45; 10 mm chemically strengthened soda-lime glass 44; 0.6 mm PVB 43; 8 mm chemically strengthened soda-lime glass 42; 1.2 mm PVB 41 and 6 mm Poly(methyl methacrylate) PMMA 40. While the lateral confinement 2 comprises: acoustic matching cement intermediate layers 34; armored steel main plates 35; high density polymer filling layers 36 and armored steel frame 37.

FIG. 4 shows an alternate version of the armored window shown in FIG. 3, in which only some layers of the armored laminate 31 are pre-stressed.

In several embodiments, each main plate has a thickness in the range of about 1 to about 10 mm and is made of a material selected from the group consisting of: high carbon steel, medium carbon steel, alloy steel, aluminum, maraging steel, tungsten carbide, high carbon steel and nickel alloys.

In some embodiments, the outer frame has a thickness in the range of about 2 to about 10 mm and is made of a high carbon steel selected from the group consisting of MIL A- 46100, MIL A-12560 and MIL A-46177.

In several embodiments, each intermediate layer has a thickness in the range of about 0.2 to about 10 mm and is made of a material selected from the group consisting of silicon, acoustic matching cement, rubber, polybutadiene, synthetic rubber, HDPE, polypropylene, polyester and PET.

In some embodiments, each filling layer has a thickness in the range of about 0.2 to about 10 mm and is made of material selected from the group consisting of silicon, acoustic matching cement, rubber, polybutadiene and synthetic rubber.

It must be understood that this invention is not limited to the embodiments described and illustrated above. A person skilled in the art will understand that numerous variations and/or modifications can be carried out that do not depart from the spirit of the invention, which is only defined by the following claims.