Metal, Matrix-fiber Composite Armor

Abstract

A high strength lightweight armor material consisting of metal composites rengthened by high density wire, fiber, or whisker elements, and which is particularly effective against more sophisticated weapons such as shaped charges and tungsten cored projectiles.

Description

The invention described herein may be manufactured and used by or for the government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION

This invention relates to improvements in armor construction which may be employed as protective covering for ships, tanks, or other mobile equipment and which is effective to absorb the energy from both high velocity projectiles and low velocity fragments of exploded metal cases.

While high velocity projectiles are defeated or resisted by armor materials having a high degree of hardness, such materials to be fully effective must also have high strength and toughness to prevent shattering and shear punching.

Similarly, high strength materials are also needed to defeat armor penetration from shrapnel produced by exploding projectiles. However, the effective shear strength of the high strength materials is limited since defeat is due largely to shear punching by reasonably large, low velocity fragments of exploded metal cases.

Fiber strengthened materials offer a strength increase by a factor of up to 10X for light metals, with a corresponding increase in modulars of elasticity and with a comparatively small density increase. This increase in strength can be utilized to defeat projectile fragments from both high and low velocity missiles with a considerable weight saving in the armor material as compared with the strength-density ratio of a similar homogeneous material.

The defeat of the projectile fragments from missiles such as shaped charges requires the diffusion of a jet-particle stream established by the projectile when detonated at a predetermined distance from a target. The normally effective penetration of armor panels by the jet-particle stream from shaped charges occurs as the result of a phenomenon known as the Munroe effect.

Prior art armoring generally required the use of materials having substantial thickness in order to reduce or diffuse projectile penetration. The resulting effect of thick armor plating was an increase in both the bulk and weight of the material and a decrease in the effective payload of the protected vehicle. Moreover, the mobility of such armored equipment was considerably hampered by the weight and bulk factors.

Other prior art armor panels consist of laminate structures having a central layer of material comprising a shock absorbing substance such as a cellular or foam plastic composition disposed between layers of face hardened steel. Such constructions, while decreasing the weight of an entire armor assembly further increased the bulk of the armor plating with consequent effects on the mobility of the protected vehicle.

SUMMARY

The instant invention solves the aforementioned problems and overcomes the disadvantages of the prior art by using an aluminum alloy panel having a core material consisting of a high density distribution of high tensile strength wires, fibers, or whiskers, having characteristics which permit suitable bonding with the aluminum, said fibers and whiskers being respectively fine and ultra fine wire.

A panel constructed in the manner of the invention has its modulus of elasticity increased 10 times with a comparatively small increase in the density of the unit.

It is well known that the effectiveness of a shaped charge is attributed to three factors, the high velocity of the mixture of gas and minute particles which emanates from the explosion, the high temperature of the mixture, and the abrasive effect which the mixture has on armor shielding.

An effective shield against a shaped charge must therefore be able to diffuse the jet-particle stream which emanates therefrom. Otherwise, the relative density law concerning homogeneous metals, applys and the effectivness of metal armor shielding is generally proportional to its density.

Accordingly, applicant has discovered that armor panels having a discontinuous density are effective to diffuse the jet stream of a shaped charge. In the disclosed invention the high tensile strength fibers are arranged in either a parallel array or a matrix, and provide the discontinuous structure. An armor panel constructed of a homogeneous aluminum alloy, although effective against projectiles and shrapnel, has little effect against a shaped charge, and is present in the invention used mainly as a binder for the fibers.

Accordingly, it is the primary object of this invention to provide armor panels having superior resistance to the impact effect of offensive weapons such as shaped charges.

Another object is to provide an improved armor construction which is capable of being used in place of comparatively thick metal plate.

Still another object of this invention is to provide a lightweight armor material which is limited as to weight and thickness.

A further object is to provide armor panels which will protect a combat vehicle against the penetrating effects produced by the Munroe jet phenomenon.

Other objects and advantages of the invention will become apparent after a study of the following specification, claims and the accompanying drawing in which:

FIG. 1 is a cross-section through a protective panel having an eight layer unidirectional wire pattern.

FIG. 2 is a panel section taken along lines 2--2 of FIG. 1.

FIG. 3 is a cross-section through an armor panel having an eight-ply orthogonal fiber lay-up.

FIG. 4 is a panel section taken along lines 4--4 of FIG. 3.

FIG. 5 is a portion of a panel member partly in elevation and partly in section showing a cross-ply arrangement of wire elements.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The accompanying drawings are primarily intended to illustrate several presently preferred fiber or wire arrangements within an aluminum matrix.

In FIG. 1, for example, the panel, generally identified at 10, comprises layers 12 and 13 of a projectile resistent, lightweight aluminum alloy, such as 2,024 aluminum alloy. An eight layer unidirectional fiber array 14 is disposed within the layers of aluminum as a reinforcing material.

The fiber or wire array comprises not less than 25 percent of the volume of the composite panel and may be formed by a single strand lay-up process or by using a prefabricated cloth material.

Although stainless steel wire is a preferred material for reinforcement purposes in the construction of the armor panel of the invention, other elements which satisfactorily bond with the aluminum alloy and which increases the tensile strength of the composite, may also be used. For example, fibers of boron and beryllium may be employed in the formation of the armor matrix.

In a preferred light metal armor panel construction, boron fibers may be embedded in aluminum alloy 2,024-T6 to provide tensile strengths of up to 187,500 psi. Since boron is less dense than aluminum, the aluminum-boron composite is considerably lighter than a homogeneous alloy having the same strength-density ratio.

Similarly, an armor panel consisting of stainless steel wire diffusion bonded into 2024 aluminum such that 25 percent of the volume of the composite is attributable to the wire achieves tensile strengths of 172-174 ksi. This represents a tensile strength increase of 300 percent over a homogeneous aluminum alloy with a density increase of only 40 percent.

In FIG. 3, the panel 15 consists of metallic layers 16 and 17 of an aluminum alloy and a reinforcing wire assembly 18 disposed intermediate the aluminum layers. In the embodiment illustrated by FIG. 3, the wire assembly is fabricated by laying up the wires in each individual layer at right angles to the wires of each adjacent layer.

FIG. 5 illustrates an armor panel 19 constructed in the manner of the invention wherein the wire reinforcements 20 are placed in layers having a cross-ply configuration.

The resistance of the armor panels of the invention to projectile penetration may be further enchanced by increasing the hardness of the exposed surface of the panel. This may be accomplished by vapor depositing a layer of titanium carbide 22 (FIG. 3) on that surface of the armor panel which is to be subjected to projectile bombardment. Similar hardness characteristics may also be obtained by bonding a thin layer of ceramic tile 24 (FIG. 1) to the exposed surface of the aluminum composite.

In use, the armor panels are generally made up in the outline of the vehicle or structure to be protected and are secured to the equipment by any appropriate means.

From a careful consideration of this specification, those skilled in the art will recognize that the armor panel constructions herein disclosed are considerably lighter in weight and will have a higher tensile strength characteristics than more conventional thick and heavy armor plating.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described.

Claims

Having fully disclosed the invention, what I claim and desire to secure by Letters Patent is:

1. A composite armor panel for protection from the effects of high velocity projectile bombardment and particle jet reactions from shaped charges comprising:

a lightweight panel of an aluminum alloy having first and second surfaces;

a high density distribution of regularly arranged fiber elements embedded in said panel intermediate the said surfaces thereof such that portions of said aluminum surround said fiber elements and form a bond therewith; and

a vapor deposited layer of titanium carbide on a surface of said panel which is exposed to projectile bombardment.

2. The armor panel construction as described in claim 1 wherein said fiber elements comprise an eight layer assembly of stainless steel wire.