Patent Application
20140322483
The present invention relates to a ballistic laminate. It finds particular application in conjunction with a ballistic laminate that offers both ballistic and flame retardant properties and will be described with particular reference thereto. It will be appreciated, however, that the invention is also amenable to other applications.
Ballistic resistant body armor and vehicle armor are made from either woven fabrics or unidirectional fabrics comprising high performance fibers such as ultra-high-molecular-weight-polyethylene (UHMWPE) fibers, aramid fibers, and glass fibers, etc. Unidirectional fiber reinforced composite where fibers are encapsulated in a polymeric matrix materials generally has better ballistic resistance than traditional woven fabrics.
Various unidirectional composite constructions are currently used for formation of soft and hard armors in ballistic protection applications. Some composite constructions use high performance fibers such as UHMWPE fibers in matrix materials. However, some high performance fibers such as UHMWPE fibers are flammable when exposed to fire and heat. There is a growing demand for fire resistance armors.
One conventional composite construction use a layer-by-layer hybrid composite construction (i.e., one or more layers comprising flame resistant fibers and one or more layers comprising flammable fiber to improve the flame resistance of the composite). One multilayer composite design includes one or more first layers of flammable fibers in a matrix and at least one second layer adjacent to the first layer. The second matrix includes a fire retardant material. The second matrix is different than the first matrix.
Another conventional composite construction includes at least one layer of UHMWPE fibers or aramid fibers in a matrix and at least one fire retardant layer. The fire retardant layer includes a fire retardant agent that absorbs heat when exposed to fire and heat in a matrix. The matrix includes one ore more relatively high chart yield resins that results in better flame resistant performance.
Another conventional composite construction includes a molded ballistic panel for use in aircraft and land vehicles for structural, ballistic, and fire resistant performance. The molded panel is formed by inserting a honeycomb between panels including non-woven high performance fiber layers and one or more fire resistant fiber layers.
U.S. Pat. No. 7,288,307 to Bhatnagar, et al. discloses hybrid laminated unidirectional fiber sheets produced from continuous roll of unidirectional prepregs, having application for impact absorption, ballistic resistance, and penetration resistance. The laminated unidirectional fiber sheets include two or more types of unidirectional fibers with different composition in a matrix. The two or more types of fibers are arranged in a side by side position. The periodic distance between fibers that have the same composition is not greater than 9 mm. However, neither distinguishes flame resistant fibers compared with flammable fibers nor gives any description on hybrid fiber-by-fiber composite constructions and/or fiber arrangements that improve the flame resistance performance of a composite.
The present invention provides a new and improved apparatus and method which addresses the above-referenced problems.
In one aspect of the present invention, it is contemplated that a ballistic laminate includes a layer including first fibers of a first material oriented at both a first direction and a second direction and second fibers of a second material oriented at both the first direction and the second direction. The first fibers are flammable, and the second fibers are flame retardant. A periodic distance greater than about 9 mm is between the second fibers of the second material oriented at the first direction. A periodic distance greater than about 9 mm is between the second fibers of the second material oriented at the second direction.
In the accompanying drawings which are incorporated in and constitute a part of the specification, embodiments of the invention are illustrated, which, together with a general description of the invention given above, and the detailed description given below, serve to exemplify the embodiments of this invention.
With reference to
As shown in
It is contemplated that the first fibers 14 of the first material 16 are relatively more flammable than the second fibers 20 of the second material 22. In one example, the first fibers 14 of the first material 16 may have a Limiting Oxygen Index (LOI) less than or equal to 25, and the second fibers 20 of the second material 22 may have an LOI greater than 25. LOI is defined as the minimum amount of oxygen required in the mixture of oxygen and nitrogen, expressed as a percentage, to support combustion of fibers. The higher the LOI, the more flame retardant fibers are. Usually, fibers with an LOI higher than 25 are considered to be flame retardant (e.g., resistant), while fibers with an LOI less than or equal to 25 are considered flammable. Therefore, in this embodiment, the first fibers 14 of the first material 16 are flammable, while the second fibers 20 of the second material 22 are flame retardant. In one example, the first fibers 14 of the first material 16 are UHMWPE in a matrix. However, it is also contemplated that the first fibers 14 of the first material 16 may be polypropylene fibers in a matrix, or any other fiber having an LOI less than or equal to 25.
In one example, the second fibers 20 of the second material 22 are at least one of aramid fibers and liquid crystal polymer (LCP) fibers. However, it is also contemplated that the second fibers 20 of the second material 22 may be at least one of glass fibers, PBO fibers, carbon fibers, ceramic fibers, PTFE fluoropolymer fibers, and steel wires, or any other fiber having an LOI greater than 25.
With reference to
With reference to
For ease of illustration, first fiber bundles or fiber tapes 6411 to 6441 and 6412 to 6442 (collectively 64) (hereinafter the first fiber bundles) including the first unidirectional fibers 14 (see
A periodic distance between second fibers 20 of the second material 22 is a distance between a last of the second fiber bundles 66 in one of the second sections 36 and a first of the second fiber bundles 66 in a next, adjacent one of the second sections 36. For example, the distance between a last of the second fiber bundles 6631 positioned substantially along a right edge of a first one 361 of the second sections 36 and a first of the second fiber bundles 6612 positioned substantially along a left edge of a second one 362 of the second sections 36 is the periodic distance between the second fibers 20. For ease of illustration, only four (4) of the first fiber bundles 64 are illustrated in the first sections 34, and only three (3) of the second fiber bundles 66 are illustrated in the second sections 36.
In the illustrated embodiment, the periodic distance 40 between second fibers 20 of the second material 22 in the first direction D1 of the first ply 30 is greater than a predetermined distance. In one embodiment, the predetermined distance is about 9 mm. Similarly, with reference to
With reference again to
Although
With reference to
It is to be understood that additional layers are constructed similar to the first layer 12.
The layers include respective first layers 12, which have a periodic distance greater than about 9 mm between the second fibers 20 of the respective second material 22 oriented at both the first and second directions D1, D2, respectively, have been found to provide good ballistic performance while, at the same time, providing desirable flame resistant properties. Although it would be expected that increasing the amount of second fibers 20 of the second material 22, which are flame retardant, would increase the flame resistant properties of the layers, the opposite has been found to be true. However, when the first fibers of the first material are UHMWPE fibers, increasing the amount of second fibers 20 of the second material 22 would decrease ballistic resistance properties of the layers.
Experimentation was conducted on layers including alternate first fibers 14 of the first material 16 (i.e., UHMWPE in the experiment) and second fibers 20 of the second material 22 (i.e., aramid in the experiment). The alternate first fibers 14 of the first material 16 (UHMWPE) and second fibers 20 the second material 22 (aramid) did increase the flame resistant properties of the laminate layers, but offered relatively low ballistic performance compared to laminate layers including only first fibers 14 of the first material 16 (UHMWPE). The laminate layers described herein provide between about 90% and about 96% of the ballistic performance of the laminate layers including, only first fibers 14 of the first material 16 (UHMWPE), while also providing similar or the same level of flame resistant properties of the laminate layers including alternate first fibers 14 of the first material 16 (UHMWPE) and second fibers 20 of the second material 22 (aramid).
Flame resistance of a hard panel comprising multiple laminate layers was determined in accordance with FAR 25,853, Appendix F, Part I, 60 second vertical burn test standard. In the test, a testing specimen of 3″×12″ is vertically mounted on a sample holder. A flame is then applied to the edge of bottom of the tested specimen for 60 seconds and then removed. The flammability requirements are as follows. Average burn length should be less than 6 inches; average flame time after removal of a flame should be less than 15 seconds; drippings may not continue to burn more than 3 seconds. In order to compare flammability of the tested hard panels made with laminate layers of different materials, the comparison should be conducted at the same thickness of the test specimen. As showed in Table 1 and Table 2, one of the hard panel made with laminate layers including only first fibers 14 of the first material 16 (UHMWPE), which is relatively more flammable, burned the entire length of a specimen of 3″×12″ when exposed to a flame. The UHMWPE/aramid hybrid hard panel at the thickness of 0.10 inches made with laminate layers including alternate first fibers 14 of the first material 16 (UHMWPE) and second fibers 20 of the second material 22 (aramid) only burned about 2.5″ of the 12″ length when exposed to a flame. The hard panel at thickness of 0.10 inches made with laminate layers including only second fibers 20 of the second material 22 (aramid), which is relatively more flame resistant, burned about 1.5″ to 2.0″ of the 12″ length of the panel when exposed to a flame. The UHMWPE/aramid hybrid hard panels at thickness of 0.10 inches made with laminate layers described above burned about 2.6″ of the 12″ length when exposed to a flame, which did burn more than the panels made with the laminate layers including only second fibers 20 of the second material 22 (aramid) and burnt the almost same length with the panels made with the laminate layers including alternate first fibers 14 of the first material 16 (UHMWPE) and second fibers 20 of the second material 22 (aramid).
The hard UHMWPE/aramid hybrid panels made with laminate layers at the thickness of 0.05″ described above burned 3.0″ of the 12″ length when exposed to the flame, which burned less than both the panels made with the laminate layers including only second fibers 20 of the second material 22 (aramid) and the UHMWPE/aramid hybrid panels made with the laminate layers including alternate first fibers 14 of the first material 16 (UHMWPE) and second fibers 20 of the second material 22 (aramid). Compared to UHMWPE/aramid hybrid panels as described above, the UHMWPE/LCP hybrid panels made with the laminate layers that have a periodic distance greater than about 9 mm between the LCP (flame retardant) fibers showed the better flammability and ballistic performance. The additional ballistic performance offered by the laminate layers described above is desirable. Any material that burns less than about 6″ of the 12″ length when exposed to a flame is acceptable for its flame resistant properties per the FAR 25.853 60 seconds vertical burn test standard.
With reference to
With reference to
As discussed above, the periodic distance between the second fibers 20 of the second material 22 oriented at the first and second directions D1, D2, respectively, are greater than about 9 mm.
The first and second plies 30, 32 are positioned adjacent to one another, as discussed above, to form the first layer 12. Additional plies are optionally positioned adjacent each other to increase a thickness of the first layer 12.
While the present invention has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention, in its broader aspects, is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant's general inventive concept.
