Splinter resistant composite laminate

Abstract

A composite component includes splinter arrestors laminated transverse to the fiber orientation of an outermost composite material layer. The splinter arrestors are located upon the outermost composite material layers at a predetermined distance from each other to constrain a splinter of fibers from the outermost composite material layers to an acceptable length.

Description

BACKGROUND OF THE INVENTION

[0002] The present invention relates to fiber reinforced resin matrix composites and, more particularly, to a composite laminated structure which resists splintering typical from ballistic impacts.

[0003] Articles fabricated from fiber reinforced resin matrix composite materials, e.g., Kevlar, graphite, and fiberglass, are known and have found increasing use in load bearing structural applications due to their high strength, light weight, and ability to be fashioned into complex shapes. Such composite structural materials are particularly suitable for aircraft structures.

[0004] A composite component is typically formed through a lay-up of composite material layers. The lay-up technique employs the use of a multiple of discrete plies of a substrate material having a plurality of parallel fibers that are impregnated with a resinous material. The multiple of layered plies are laminated in a mold and then placed in an autoclave or oven for application of heat and pressure such that the lay-up cures into the finished composite component.

[0005] To maximize the benefits of composites, it is essential that the fiber orientation be optimally tailored to meet the strength and stiffness requirements for a particular application. Disadvantageously, the outermost layers or plies of the composite component include a single fiber orientation, which may be subject to splintering or peeling in response to impact hazards. Since composites have relatively low interlaminar peel strength, the splinters may become relatively long. These elongated splinters may compromise structural integrity. A relatively small puncture may thus damage a relatively larger area. Even if integrity is not an issue, the repair covers a large area through which the splinter extends.

[0006] Accordingly, it is desirable to provide a composite laminate which resists splintering when damaged particularly from ballistic impact.

SUMMARY OF THE INVENTION

[0007] The composite component according to the present invention includes splinter arrestors laminated transverse to the fiber orientation of an outermost composite material layer.

[0008] The splinter arrestors are tows located upon the outermost composite material layers at a predetermined distance from each other. The predetermined distance is a distance which will constrain a splinter of fibers from the outermost composite material layers to an acceptable length. Alternatively or in addition, tows may be eliminated in subsurface layers to avoid an increase in the overall weight of the composite component.

[0009] The present invention therefore provides a composite laminate which resists splintering when damaged, particularly from ballistic impact.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:

[0011] FIG. 1 is a general exploded view of a composite component;

[0012] FIG. 2 is a general perspective view of a single tow of a plurality of fibers;

[0013] FIG. 3 is a general perspective view of a composite component illustrating splinter arrestors according to the present invention; and

[0014] FIG. 4 is a general exploded view of another composite component with subsurface tows which correspond to the splinter arrestors eliminated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0015] FIG. 1 illustrates an exploded view of a composite component 10 manufactured from a plurality of prepreg composite material layers 12 which are selectively oriented and selectively chosen to achieve the desired strength. The plurality of prepreg composite material layers 12 may be laid up upon each other or may skin a core material 14 such as honeycomb, foam, or the like. The actual lay-up of one or more prepregs is well known and further description of the details thereof need not be provided herein.

[0016] Each material layer 12 is preferably manufactured of unidirectional fiber material which is laid down as a plurality of parallel tows. That is, each material layer 12 includes a plurality of tows 12t (FIG. 2) which are manufactured as a bundle of continuous monofiber strands. As will be apparent, each tow or tow strand is essentially a bundle of a plurality of fiber filaments. Suitable fibers include high strength fibers such as graphite fibers, fiberglass fibers, ceramic fibers, and aramid fibers, which are commercially available. The outermost composite material layers 12′ define a single fiber orientation which may be subject to splintering or peeling in response to damage. That is, one or more tows may be peeled away from a subsurface layer.

[0017] To prevent peeling of the outermost composite material layers 12′ splinter arrestors 16 are located transverse to the single fiber orientation of the outermost composite material layers 12′. The splinter arrestors 16 are preferably individual tows oriented perpendicular to the direction of the tows 12t within the outermost composite material layers 12′ (FIG. 2). Suitable splinter arrestors 16 include high strength fibers such as graphite fibers, fiberglass fibers, ceramic fibers, and aramid fibers, as well as lower strength fabric tape, woven cloth, and/or nonwoven fabric of interbonding fibers. Fiber placement machines are preferably utilized to locate single splinter arrestor tows 16t upon the outermost composite material layers 12′. Relatively wider tows, multiple tows, or tapes will also benefit from the present invention. The outermost layer is formed as a checkerboard-like pattern. It should be understood that various automated and hand layup methods of layer and splinter placement will benefit from the present invention.

[0018] The splinter arrestors 16 are located upon the outermost composite material layers 12′ at a predetermined distance from each other. The predetermined distance is preferably a distance, which will constrain a splinter of fibers from the outermost composite material, layers 12′ to an acceptable length should a projectile p damage the component 10 (FIG. 3). The acceptable length will typically depend at least upon the composite component 10 size and location within a composite structure.

[0019] Referring to FIG. 4, tows 12t′ in subsurface layers which correspond to the splinter arrestors 16 may be eliminated such that the overall weight of the composite component 10 is not increased. Preferably, the tows 12t′ which are oriented in the same direction and are directly below the splinter arrestors 16 are eliminated. The eliminated tows 12t′ need not be immediately below the outermost composite material layers 12′ but may be within a deeper subsurface layer within the composite component 10′.

[0020] The foregoing description is exemplary rather than defined by the limitations within. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.

Claims

1. A composite component comprising:

a plurality of composite material layers comprising an outermost layer having a plurality of non-metallic tows, each of said non-metallic rows separated by a first distance; and

at least two non-metallic splinter arrestors laminated to said outermost layer of said plurality of composite material layers, said at least two non-metallic splinter arrestor arrestors oriented substantially transverse to a fiber direction of said outermost layer, said at least two non-metallic splinter arrestors separated by a second distance greater than said first distance.

2. The composite component as recited in claim 1, wherein said at least two non-metallic splinter arrestors and said non-metallic tows are formed of graphite fibers.

3. The composite component as recited in claim 1, wherein said splinter arrestor comprises a tow.

4. The composite component as recited in claim 1, wherein said splinter arrestor comprises a monofilament.

5. The composite component as recited in claim 1, wherein said splinter arrestor comprises a fabric tape.

6. The composite component as recited in claim 1, further comprising a subsurface composite material layer of said plurality of composite material layers below said outermost layer, said subsurface layer having a plurality of non-metallic tows and at least two gaps separated by said second distance, said two gaps located directly below said at least two splinter arrestors.

7. A method of manufacturing a composite component comprising the steps of:

(1) laminating at least two non-metallic splinter arrestors to an outermost layer of a plurality of composite material layers, the at least two splinter arrestors substantially parallel to each other and transverse to a non-metallic fiber direction of the outermost layer to limit peeling of the outermost layer to the distance between the at least two splinter arrestors in response to a projectile passing through the composite component.

8. A method as recited in claim 7, wherein said step (1) further comprises laminating a plurality of relatively parallel splinter arrestors spaced a predetermined distance from each other to the outermost layer, the predetermined distance greater than a first distance between each of a plurality of twos in the outermost layer.

9. A method as recited in claim 7, wherein said step (1) further comprises eliminating tows in a subsurface composite material layer which correspond in orientation to the splinter arrestor.

10. A method as recited in claim 7, wherein said step (1) further comprises eliminating tows in a subsurface composite material layer which are parallel to and below the splinter arrestor.

11. The composite component as recited in claim 1, wherein said at least two non-metallic splinter arrestors and said non-metallic tows are formed of fiberglass fibers.

12. The composite component as recited in claim 1, wherein said at least two non-metallic splinter arrestors and said non-metallic tows are formed of ceramic fibers.

13. The composite component as recited in claim 1, wherein said at least two non-metallic splinter arrestors and said non-metallic tows are formed of aramid fibers.

14. A composite component comprising:

a plurality of composite material layers comprising an outermost layer having a plurality of tows, each of said tows separated by a first distance; and

a plurality of splinter arrestors laminated to said outermost layer of said plurality of composite material layers, said plurality of splinter arrestors oriented substantially transverse to said plurality of tows of said outermost layer, at least two of said plurality of splinter arrestors separated by a second distance greater than said first distance to limit peeling of the outermost layer to said second in response to a projectile passing through the composite component.

15. The composite component as recited in claim 14, wherein each said plurality of non-metallic splinter arrestors are fabric tapes.

16. The composite component as recited in claim 14, wherein each said plurality of non-metallic splinter arrestors and each of said plurality of tows are manufactured from non-metallic monofiber strands.

17. The composite component as recited in claim 16, wherein each said plurality of splinter arrestors are tows.

18. The composite component as recited in claim 16, wherein each said plurality of splinter arrestors arc single monofilament.