US20100275765A1

US20100275765A1 - Shape-effect composite armor system

Info

Publication number: US20100275765A1
Application number: US12/658,723
Authority: US
Inventors: James Thomas LaGrotta; Richard Thomas LaGrotta; Alexandra Charles LaGrotta
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-02-26
Filing date: 2010-02-16
Publication date: 2010-11-04

Abstract

An armor system for protecting an object from the impact of a projectile. A core layer of hardened metal or ceramic balls supported in a softer material, wherein the surfaces of the balls are in contact with adjacent ball surfaces and the sizes of the balls are selected with respect to the anticipated shape of the projectile being armored against. Inward and outward facing reinforced layers at the surfaces of the core layer. The reinforced layers including a resin base and fibers therein. A backing plate may back the core layer on the rear surface.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 61/208,563, filed on Feb. 26, 2009, incorporated herein by reference.

BACKGROUND OF THE INVENTION

There is a pressing need for lightweight armor systems to protect military and civilian vehicles and equipment. Existing armor systems are often heavy and expensive, and often rely on Rolled Homogeneous Armor (RHA) plates which are heavy and difficult to fabricate into shaped armor systems.
A breakthrough in armor systems would be a system that is lighter than conventional armor, while also being formable into complex shapes and being producible at a reasonable cost.

SUMMARY OF THE INVENTION

Disclosed herein is a composite armor system that preferably combines the hardness of steel with the toughness of a plastic composite, with a weight reduction believed to be 30-40% below RHA and produced at reduced fabrication costs.
The armor takes advantage of an effect that a shaped surface of hard material has on a projectile that strikes the surface. The incoming projectile interacts with the armor in several basic ways. First, the projectile is physically blunted and deformed by a high-speed interaction with the hard, curved outer surface of the armor. Second, the projectile is deflected from its original path, thereby transferring a portion of its forward momentum into the plane of the armor. Third, the energy of the projectile is spread over a larger surface area along the direction of the entire travel of the projectile. Lastly, the armor system spreads the projectile's energy in the plane of the armor as the projectile is trapped between adjacent curved surfaces.
The armor system is a composite structure comprised of at least one and preferably two reinforced outer layers wherein each reinforced layer is at one side of and two of the reinforced layers are on opposite sides of and surround one or more hardened and correspondingly shaped inner layers (called core layers). The reinforced layers are of a resin strengthened by included fibers. The core layer is also of a resin which includes preferably one layer that contains an array of small size balls all touching adjacent balls in the array. Each ball is sized to about the size of a projectile to be armored against. The balls are of metal or a ceramic. They are of a material such that they have a surface hardness at least as hard as or harder than the impact surface of the projectile expected to strike the armor.
An array of reinforcing wires connect the projectile facing outer layer to the core layer.
The basic armor system described herein is preferably a three-layer armor. But, it can be expanded with additional core and/or reinforced layers in various arrangements to address increased threat levels, and provide greater strength or penetration resistance or protect against other unique projectiles.
Other objects and features of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary and cut away perspective view of a first embodiment of an armor system embodying the invention.

FIG. 2 is a fragmentary cut away view of a second embodiment; and

FIG. 3 illustrates a shaped armor.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the cutaway view of an armor system in FIG. 1, the system includes several layers. There is a core layer 13. There are shown preferably two, opposite reinforcing layers at the opposite surfaces of the core layer, including outer layer 11, which will face outwardly from the object on which the armor is placed and toward an incoming projectile, and inwardly facing inner layer 15, which will face inwardly toward the object that is being protected by the armor. In order that the object being protected itself provides at least one support for the armor, the inner reinforced layer 15, to the extent possible, is shaped to the shape of the surface of the object on which the layer 15 is applied (see FIG. 3), so that the object helps the armor resist any projectile and thereby protects the object that is armored. The other layers will have a shape that corresponds to the shape of the inner layer.
The reinforced layers 11, 15 that are placed at the front and rear of the armor system are comprised of a known thermoplastic resin, which is a bonding resin, described below. The resin is highly-loaded, at about 70 to 80% by volume of added reinforcement material, comprised of E glass fibers of relatively long length, e.g., 3 to 6 inches. Use of this fiber length may preclude the use of standard injection molding of the layers, so the reinforced layers are compression molded using heat to reflow the thermoplastic Bonding Resin. The fiber reinforcement may also be stronger S-glass fibers, Kevlar, other specialty fibers, carbon fibers, nanotubes or other materials of this type. The fibers are randomly arranged in three dimensions in their respective layers to prevent delamination of the layers or of the armor upon projectile impact, as delamination typically occurs with mat-based systems. However, in some situations it may nonetheless be desirable to use a mat-based reinforcement material. That material is also cheaper due to the reduced pre-processing needed to fabricate the reinforcement fibers. The fiber systems are broken down into small groups of fibers or even single fibers to maximize the interaction of the fibers with the bonding resin.
One example of the bonding resin in the reinforced layers is preferably finely-powdered, preferably having a particle size of 0.002 inches to 0.010 inches and preferably comprised of a polycarbonate, which is selected for its toughness and thermal formability. It is alternatively possible to use thin sheets of the desired thermoplastic to form the composite structure. The fine powder assures a high level of surface contact with the fiber reinforcements. The use of a thermoplastic allows forming the armor in flat sheets and then re-forming the sheets (see FIG. 3) into more complex shapes through re-heating and pressing them. Very complex shapes can also be formed in a final or near-final stage. This enables shaping the armor to the object armored.
Alternative bonding resins can be selected to vary the properties of the reinforced layers and the armor system. These resins include other thermoplastic resins as well as thermosetting materials such as epoxies. The bonding resin may be solid and homogenous through its thickness, or it may be varied by the addition of microspheres or foaming agents, primarily used to reduce weight in part or all of the layer's thickness. These modifications can be made in some or all reinforced layers and in any combination.
The thickness of each reinforced layer may be between 0.10 inches and 0.6 inches. The thickness may be varied within or outside of this range dependent on the threat level of projectiles which may impact the armor. The outer and inner reinforced layers may also be of different respective thicknesses to optimize the design for a particular use.
In the first embodiment of FIG. 1, the core layer 13 is generally flat or planar as are the reinforced layers 11, 15. In the alternative third embodiment of FIG. 3, the core layer 33 is curved in shape to rest on and conform to the surface 38 being armored, for example. The inner reinforced layer has a curved surface 37 to conform to the curved surface 38 to be armored. The inner and outer reinforced layers 35 and 31 are correspondingly curved or profiled on their inward facing surfaces to fit to the core layer and make a firm composite armor arrangement. Shown in broken lines in FIG. 3 is curved area 38 of an object, like the surface of a vehicle shown in broken lines, and the armor is correspondingly curved or shaped to the surface there armored.
The core layer 13, 23, 33 (of FIGS. 1, 2 and 3) is comprised of hard material, preferably e.g., ⅜″ diameter surface-hardened steel balls 16, 26. For best performance, the balls 16, 26 are in a single layer and are there in a tightly-arrayed design. For example, the array of balls is so tight that the outer surface of each ball is normally preferably in touching contact with the outer surface of adjacent balls in the core layer and three adjacent balls define and surround an open area, into which, for example, a below described reinforcement 14 may extend.
Each ball 16 is preferably of a size on the same order of magnitude as the projectile against which the armor protects. Very small balls relative to a projectile to be protected against may act as a homogeneous material and may be simply displaced by the projectile. Very large balls are heavy and may make the armor unnecessarily heavy due to added thickness of the core layer due to the ball size. If the balls are very large, they may approach acting as a flat plate and then they would not interact with the projectile.
The balls are preferably of a material and are so constructed as to have a surface hardness of at least about the same hardness as the impact surface of a projectile against which the armor protects, or a greater hardness. Such balls may be of a hardened steel, a hardened ceramic, another hardened metal, including aluminum. In particular, the surface of the ball is hard.
Other designs for the core layer 3 could use different-sized balls, hollow steel balls to reduce weight, through-hardened balls, solid or hollow balls of other hard materials such as ceramics. Use of the balls allows for simple post-forming of the thermoplastic-based reinforced layers since the balls are not formed into a rigid sheet, like a plate of steel.
A key element is a discontinuity between the hardness of the center core layer and the relative softness of the front or outward reinforced layer. Hard spheres in a matrix of hard material in the core layer do not present this discontinuity to the projectile.
The composite armor structure is then reinforced in a direction perpendicular to the plane of the layers and at least in part in the direction of a path of a projectile, called axial reinforcement, preferably by incorporation of short length, high-strength steel wires 14 with a preferred diameter that is preferably less than or equal to the space defined between and surrounded by each array of three touching balls in the layer 13. This avoids wires forcing contacting balls apart, which would disrupt a pattern of balls in layer 13 and could prevent some balls touching neighboring balls in a pattern with a preferred about 1 inch spacing between wires. This spacing can be varied depending upon the projectile expected to be stopped. The individual spaced apart axial reinforcement elements extend at least through the reinforced layer that may be impacted by the projectile and optionally, but preferably, extend further partially at least through the adjacent core layer. Without such reinforcement perpendicular to the surface of the armor, the system may delaminate upon impact. Because the reinforced layers may be mats of woven glass, the reinforcement wires are bent over at their ends or have end fixtures that reduce the chance the reinforcement wires will move out of the plastic material of the armor layers.
Other materials and systems can be used to provide the placement of the balls and the axial reinforcement of the layers. The balls can be mechanically held in place during a portion of the fabrication of the center core layer. The axial reinforcement can be provided by using the same fiber material as is used in the reinforced layers or using a different material, such as those mentioned as candidate reinforcements above.
An alternative embodiment of the armor is shown in FIG. 2. Except as described here, it may be the same as the first embodiment. The core and reinforced layers 23 and 21, 25 may be the same as in FIG. 1 and have the same reference numbers raised by 10. The balls 26 in the core layer 23 are ground flat on their rear facing surfaces 27 toward the object to be armored. The balls may be ground to a depth of approximately 30% of the diameter of the ball. Grinding more off the balls, e.g., 50% may cause the balls to ride up on neighboring balls instead of pressing against them. This removal of part of the balls reduces the areal density of the core layer and therefore of the armor. The balls 26 are supported by a thin steel back plate 22. The plate 22 further spreads the energy from a projectile impact onto a larger area of the rear or inner reinforcement layer 21, increasing the stopping power of the armor. The make-up and properties of the back plate can be optimized for a specific projectile and armor application.
The core layer 13, 23, 33 can also be formed as a unified structure either by removal of material e.g., EDM of a hardened steel plate, or by deposition of material e.g., powder metallurgy or plating processes, or by forming e.g., forging and then hardening of steel plates. This simplifies fabrication of the core by trading off flexibility and post-formability.
It is envisioned that this armor system can be manufactured in large plates in a vertically-oriented process. The first stage of manufacture forms the core structure. Simple optical inspection is possible since the balls are easily visible.
The second stage applies the reinforcement layers 11 and 15 to the front and back of the core layer 13 to the desired thicknesses, then applies the axial reinforcements 14. A final inspection may be made with a non-destructive method such as ultrasonic or x-ray to detect any gaps or missing balls in the core layer or voids in the reinforcement layers.
Sheets of the armor can be made as wide and long as fabrication equipment permits, typically on the order of 5 to 10 feet wide and 10 to 20 feet long. Post-forming can be done with thermoplastic based systems to achieve curved surfaces as long as the above described inherent structure of the layers is preserved. Complex shapes with tight radii could be formed in the net-shape with dedicated tooling.
Prototypes of the armor system have been designed, built, and tested. During observations by the inventors hereof, the armor systems hereof have demonstrated excellent stopping power as well as excellent areal density values, making this a viable and attractive product for the defense and commercial armor markets.
Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.

Claims

1. Armor system for application to an object to be armored, wherein the armor system is intended to stop passage of a projectile, the armor system comprising:

a core layer comprising:

a tightly arrayed pattern of a layer of hardened balls in the core layer, wherein the balls have a diameter of about one to two times the diameter of a projectile to be armored against and the balls have a surface hardness of about the same hardness or harder than an impact surface of the projectile to be armored against;

a material much softer than the balls disposed at the core layer and surrounding the balls for holding the balls in a layout in the core layer;

the core layer having opposite surfaces;

a reinforced layer at least one of the surfaces of the core layer for reinforcing the armor.

2. The armor system of claim 1, wherein the reinforced layer is on one of the opposite surfaces of the core layer which is outward of the object to be armored and faces toward the projectile to be armored against.

3. The armor system of claim 2, further comprising another reinforced layer on the opposite surface of the core layer inward toward the object to be armored also for reinforcing the armor.

4. The armor system of claim 3, further comprising a backing plate between the core layer and the reinforced layer at the surface of the core layer away from the projectile, wherein the backing plate is configured to prevent the balls moving out of the core layer.

5. The armor system of claim 3, wherein the inward reinforced layer has a shape selected to correspond to a shape of a surface of an object being armored by the armor system.

6. The armor system of claim 3, wherein the reinforced layer comprises fibers in a random array and supported in a resin.

7. The armor system of claim 1, wherein the balls in the core layer are hardened steel balls.

8. The armor system of claim 1, wherein the balls in the core layer are hardened ceramic balls.

9. The armor system of claim 1, wherein each ball has an outer surface and the array of balls is tight such that the outer surface of each ball is in touching contact with the outer surfaces of adjacent balls in the core layer.

10. The armor system of claim 1, wherein the armor is of reduced areal density by having removed from the balls a fraction of the material of each of the balls, wherein the removal comprises at least one of a flat formed on a rear surface of the ball facing away from the side thereof to be impacted by the projectile and a hollowed area formed in a rear center of the ball.

11. The armor system of claim 1, further comprising a plurality of axial reinforcements extending across at least the reinforced layer to be impacted by the projectile and optionally extending into the core layer.

12. The armor system of claim 11, wherein each ball has an outer surface and the array of balls is tight such that the outer surface of each ball is in touching contact with the outer surfaces of adjacent balls in the core layer.

13. The armor system of claim 12, further comprising axial reinforcements located to extend into the core layer into spaces surrounded by adjacent contacting balls.

14. The armor system of claim 11, wherein the axial reinforcements are at approximately 1 inch centers apart.

15. The armor system of claim 11, wherein the axial reinforcements are of a material of high strength.

16. The armor system of claim 15, wherein the reinforcements are of steel wire.

17. The armor system of claim 1, wherein the core layer is so configured and of such material as to be bonded to a polymer based composite armor.

18. The armor system of claim 1, wherein the at least one reinforced layer is positioned on a rear surface of the core layer away from impact from the projectile and backing the core layer, and the at least one reinforcement layer is configured, shaped and positioned to restrict movement of individual ones of the balls rearwardly, with respect to the rear surface of the core layer, as a result of impact by the projectile on the armor system from a direction of an opposite front surface of the core layer.

19. The armor system of claim 1, wherein the material in the core layer surrounding the balls therein comprises a reinforced thermoset or a thermoplastic material.

20. The armor system of claim 17, wherein the material surrounding the balls in the core layer comprises a fiberglass reinforced epoxy, or a fiberglass reinforced polycarbonate, or a low-density metal or aluminum.