Composite armor material

Details Composite armor material Composite armor material

1998-10-15

2001-04-17

Carone, Michael J. (Department: 3641)

Ordnance

Shields

Shape or composition

C089S036080

Reexamination Certificate

active

06216579

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a new composite material for use in vehicle armoring.
BACKGROUND OF THE INVENTION
Presently in North America armored vehicles are engineered and manufactured primarily to provide protection against ballistic attack. The armor typically comprises a single plate, and is held in place using mechanical fasteners and/or by welding. Ballistic protection is achieved either by overlapping of several armor plates, or by covering joints with additional plates. From a mechanical strength standpoint, these armor materials are basically parasitic and do not add any significant strength to the vehicle.
More recent advances in armor materials include the use of dual hard steel. The dual property hardness steel armor has several distinct advantages over earlier prior art armor; such advantages include having requirements conducive to unlimited production quantities using existing facilities and having fabricability and intrinsic properties of steel. The earlier concept for dual property steel armor was developed from the knowledge that a high hardness was needed to shatter steel armor piercing projectiles and a high toughness was required to achieve multiple strike integrity.
Although the dual property steel armor principle provides an alloy capable of breaking up the projectile, numerous tested alloys have resulted in panel shattering. When panel shattering occurs the effectiveness of the armor is lost, particularly as an armor suitable for a multiple strike capability.
A further development of armor materials is described in U.S. Pat. No. 3,694,174, which issued on Sep. 26, 1972. That patent discloses a composite material having an outer high hardness impact layer capable of breaking up a projectile, and a lower hardness tough backing layer capable of stopping the broken up projectile. The layers are hot-rolled together to form the composite. The difference in hardness being described as being in the range of 5-8 Rockwell C. The outer layer is further described as having a Rockwell C hardness of 58-59, and the inner layer having a Rockwell C hardness of 52-53. The thickness of the layers is described as being in the range of 2-3.5 inches.
It is apparent that both layers of this material are still relatively hard. Moreover, it is unlikely that the small relative difference in hardness between the two layers would be sufficient to achieve much of a difference in mechanical properties. Further, the hot-rolling process is bound to have an adverse impact upon such properties. Also, a composite of the described dimensions would add considerable weight to a vehicle. It will be appreciated that added weight will affect vehicle performance, particularly the power and handling requirements.
It is also known, for example, from U.S. Pat. No. 4,948,673 issued Aug. 14, 1990, to employ sintered ceramic tiles e.g. based on alumina or silica, to break up armor-piercing projectiles. The broken pieces of the projectile are then stopped by an armor plate backing.
SUMMARY OF THE INVENTION
According to the invention, a novel composite armor material is provided, comprising an outer ballistic impact resistant layer of a steel material having a Rockwell “C” scale hardness of 47-54, and an inner blast resistant steel layer having a fracture toughness of 3.6-6.5 J/mm, and a Rockwell “C” hardness of 28-36.
Optionally, a synthetic resin adhesive is provided between the two layers. Depending upon the requirement, various adhesives may be employed. For example, a soft adhesive such as a polysulfide-based adhesive may be used in some embodiments and a harder adhesive such as a polyurethane-based adhesive may be used in other embodiments.
In another embodiment, a layer of a high tensile strength fabric material is provided adjacent to the inner layer. This layer is not bonded to the inner layer, since bonding would detract from its ballistic capability. Accordingly, it may be touching or slightly spaced from the inner layer and is held in place by mechanical fasteners. Also, in use, some backing space must be provided to permit the material to flex so as to act as a catcher's mitt to trap any shrapnel which may have penetrated the inner layer.
In yet another embodiment, an additional outermost layer is provided, which is of a high hard steel as described above. In this case, no bonder is present, and the steel layers are welded together.
In a further embodiment, a ceramic layer may be included as an additional outermost layer.


REFERENCES:
patent: 4131053 (1978-12-01), Ferguson
patent: 4404889 (1983-09-01), Miguel
patent: 4813334 (1989-03-01), Bloks et al.
patent: 5290637 (1994-03-01), Sliney
patent: WO 91/00490 (1991-01-01), None

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