阅读说明：本技术 等静压侧压力防护的复合材料固结 (Isostatic side pressure protected composite consolidation ) 是由 D·汤普森 于 2018-12-18 设计创作，主要内容包括：本发明公开了一种用于由复合层压堆叠材料制造弹道制品的模具,其中所述模具具有滑动密封部分,所述滑动密封部分套入外部圆周部分和基部,以便防护复合层压堆叠材料的侧部在压热器中时免于受到施加的等静压力。通过防护复合层压堆叠材料的侧部,可以将多余的树脂基质材料从复合层压堆叠材料中压出,以提供重量减轻且厚度减小的均匀的复合制品。(A mold for making a ballistic article from a composite laminate stack material, wherein the mold has a sliding seal portion that nests over an outer circumferential portion and a base portion to shield sides of the composite laminate stack material from an applied isostatic pressure while in an autoclave. By shielding the sides of the composite laminate stack material, excess resin matrix material can be pressed out of the composite laminate stack material to provide a uniform composite article with reduced weight and thickness.)

1. An isostatic composite consolidation apparatus or mould comprising a fixture that protects the side walls of a laminate from pressure while exposing the laminate and fixture together to isostatic pressure.

2. The isostatic composite consolidation apparatus or mold according to claim 1, wherein said fixing means comprises:

a circumferential portion providing pressure protection to the side wall of the laminate;

a closed profile portion that controls the curvature of the laminate; and

and a sealing portion.

3. The isostatic composite consolidation apparatus or mould as claimed in claim 1 or 2, wherein said sealing portion comprises an opening allowing isostatic pressure to be applied directly to all parts except the periphery of the surface of the laminate with which said opening is in contact.

4. The isostatic composite consolidation apparatus or mould as claimed in any one of claims 1-3, wherein said closed profile portion and said sealing portion are both in contact with said circumferential portion and a non-side wall surface of the laminate and form a sealing gap between said circumferential portion and a side wall of the laminate, said sealing portion and said closed profile portion being movable towards each other under pressure, and preferably the opposing surfaces of said sealing portion and said closed profile portion are identically profiled offsets, said offsets being determined by the thickness of the laminate.

5. The isostatic composite consolidation apparatus or mould as claimed in any one of the preceding claims, wherein said laminate and said fixing means are enclosed in a silicone membrane and heat sealed in a disposable plastic bag fused with the contents and surroundings under vacuum.

6. The isostatic composite consolidation apparatus or mould as claimed in any one of the preceding claims, wherein said silicone diaphragm comprises a plurality of separate portions.

7. The isostatic composite consolidation apparatus or mould as claimed in any one of the preceding claims, wherein said silicone membrane is sufficiently flexible to transmit the applied pressure to the exposed surfaces of the laminate and fixture without significant loss of isostatic properties.

8. A method of isostatic composite consolidation using the apparatus or mould of any of the preceding claims, wherein a heat-sealed disposable plastic bag containing a silicone membrane, the fixture and the laminate is cycled through simultaneous and controlled application of elevated isostatic pressure and temperature to consolidate the laminate.

9. The isostatic composite consolidation apparatus or mould as claimed in any one of the preceding claims, wherein said circumferential portion, said closed profile portion and said sealing portion are constructed of a rigid and strong material, such as a metal, metal alloy or composite material.

10. The isostatic composite consolidation apparatus or mould as claimed in any one of the preceding claims, wherein said material is thermally conductive.

11. The isostatic composite consolidation method, apparatus or mould as claimed in any one of the preceding claims, wherein applying pressure to said fixture is for closing the interface between said circumferential portion and said sealing portion and said closed profile portion.

12. The isostatic composite consolidation apparatus or mould as claimed in any one of the preceding claims, wherein said sealing portion is designed to deform elastically under pressure to maintain contact with said circumferential portion.

13. The isostatic composite consolidation apparatus or mould as claimed in any one of the preceding claims, wherein said circumferential portion is non-circular.

14. A mold for forming a ballistic article by consolidating a laminate stack, the mold comprising:

a sliding seal portion; and

a base profile portion having a circumferentially upwardly extending sidewall having an inner surface and a base profile surface;

the circumferentially extending side wall has an inner dimension greater than an outer dimension of the laminate stack to be consolidated;

wherein the sliding seal portion forms a sliding fit with the inner surface of the circumferentially extending sidewall.

15. The isostatic composite consolidation apparatus or mould as claimed in any one of the preceding claims, wherein said sealing portions protect the sides of the laminate stack from external pressure.

16. The isostatic composite consolidation apparatus or mold according to claim 14, wherein said sliding seal portion has an "L" shaped profile.

17. The isostatic composite consolidation apparatus or mold according to claim 16, wherein said base profile portion is slidingly placed within said sealing portion.

18. The isostatic composite consolidation apparatus or mold according to claim 17, wherein said mold further comprises a sealing ring.

19. The isostatic composite consolidation apparatus or mold according to claim 17, wherein the sealing ring is deformable.

20. The isostatic composite consolidation apparatus or mold according to claim 17, wherein said sealing ring is positioned on the back side of said base profile.

21. The isostatic composite consolidation apparatus or mould as claimed in any one of the preceding claims, wherein an inner dimension of the circumferentially extending side walls of the base profile portion is 0.001mm to 25mm larger than an outer dimension of the laminate stack to be consolidated.

22. The isostatic composite consolidation apparatus or mould as claimed in any one of the preceding claims, wherein said sealing portion is a ring or a band.

23. The isostatic composite consolidation apparatus or mould as claimed in any one of the preceding claims, wherein said sliding seal portion is a ring or a band having an angled profile.

24. The isostatic composite consolidation apparatus or mould as claimed in any one of the preceding claims, wherein said sliding seal portion is a ring or a belt having an inclined profile.

25. The isostatic composite consolidation apparatus or mould as claimed in any one of the preceding claims, wherein said sliding seal portion is a ring or a band having an "L" shaped profile.

26. The isostatic composite consolidation apparatus or mould as claimed in any one of the preceding claims, wherein said sealing portion is a hoop or band having a substantially uniform profile.

27. The isostatic composite consolidation apparatus or mould as claimed in any one of the preceding claims, wherein said sealing portion is deformable.

28. The isostatic composite consolidation apparatus or mould as claimed in any one of the preceding claims, wherein the base profile portion is two-piece.

29. The isostatic composite consolidation apparatus or mould as claimed in any one of the preceding claims, wherein the base profile portion is two-piece, comprising a base profile portion and a circumferential portion.

30. The isostatic composite consolidation apparatus or mould as claimed in claim 23, wherein a sealing diaphragm is located between said sealing portion and said laminate stack to be consolidated.

31. The isostatic composite consolidation apparatus or mould as claimed in any one of the preceding claims, wherein the mould is a moulding tool.

32. A process for preparing a molded article comprising the steps of:

forming a stack of laminates;

providing an isostatic pressing device;

placing the stack of laminates into a mold, the mold having a sliding seal portion; and

a base profile portion having a circumferentially upwardly extending sidewall with an inner surface and a base profile surface;

the circumferentially upwardly extending side wall of the base profile portion has an inner dimension greater than an outer dimension of the laminate stack to be consolidated;

applying isostatic pressure to an outer surface of the sliding seal ring;

wherein the sliding seal portion forms a sliding fit with the inner surface of the circumferentially extending sidewall under the isostatic pressure.

33. The isostatic composite consolidation method, apparatus or mould as claimed in any one of the preceding claims, wherein said moulded article is a ballistic article.

34. The isostatic composite consolidation method, apparatus or mould as claimed in any one of the preceding claims, wherein said sealing portion is deformable.

35. The isostatic composite consolidation method, apparatus or mould as claimed in any one of the preceding claims, wherein said stack of laminates has a top face, a bottom face and side faces.

36. The isostatic composite consolidation method, apparatus or mould as claimed in any one of the preceding claims, wherein said isostatic pressure is prevented from being applied onto said side of said laminate.

Background

Consolidation of thermoplastic and thermoset materials to form composite laminates has been accomplished for many years by the simultaneous application of high pressure and temperature. Such consolidation processes are typically applied in hydraulic presses with thermally regulated platens, or in autoclaves with pressurized and thermally regulated gases.

Consolidation of laminates within a hydraulic press equipped with a thermally regulated platen (commonly referred to as "hydraulic axial pressing") typically allows for the application of high levels of consolidation pressure that are directed through opposing rigid surfaces. This high level of consolidation pressure is often associated with the manufacture of high performance composite laminates. In some fields, such as the manufacture of ballistic resistant laminates, hydraulic axial pressing can produce composite articles having relatively high penetration resistance. However, hydraulic axial compaction also has limitations such as low productivity, expensive tooling, and relatively high Standard Deviation (SD) associated with ballistic test results.

Consolidation of the laminate in an autoclave containing pressurized and heat conditioned gas (commonly referred to as "autoclave treatment") typically allows the application of a low level of consolidation isostatic pressure. Such an autoclave process is widely used in industry and is associated with the production of large parts and the mass production of large quantities of parts. In some fields, such as the manufacture of ballistic resistant laminates, autoclave processing can be limited, for example, by the need for relatively high proportions of matrix (resin) to achieve adequate laminate consolidation. Most importantly, autoclave processing is associated with the manufacture of composite articles that provide relatively low penetration resistance.

An alternative to the autoclave process is to replace the liquid fluid with a gaseous fluid and then to replace the pneumatic application of consolidation pressure with hydraulic application of consolidation pressure. In this application, the process space containing the pressurized liquid fluid is referred to as a hydraulic pot, and the process is referred to as "hydraulic heat treatment". As disclosed in US 8,979,523B 2, a form of hydro heat treatment is employed in known composite consolidation processes. This process combines the production efficiency of autoclave processing with the high magnitude consolidation pressure of a hydraulic axial press.

WO2008/098771 describes a method for manufacturing a molded article using a known isostatic pressing process to consolidate a stack of laminates under very specific conditions, comprising placing the stack of specific laminates and a binder in an isostatic pressing device and consolidating under specific pressure and elevated temperature.

It has been found that for ballistic resistant laminates, the application of high levels of isostatic consolidation pressure acting on the composite laminate can adversely affect the penetration resistance of the resulting laminate.

Disclosure of Invention

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. For example, as used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items and may be abbreviated as "/".

Spatially relative terms, such as "below," "… -below," "lower," "above," "upper," and similar terms, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s), as illustrated. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures.

The present invention has been particularly designed to provide protection against consolidation pressure to the sidewalls of a composite laminate that is a stack of materials that may or may not be a prepreg material as a synthetic fiber, such as but not limited to aramid (e.g.,) High Modulus Polyethylene (HMPE) materials (e.g.,) High modulus polypropylene (HMPP), Ultra High Molecular Weight Polyethylene (UHMWPE) (e.g.,) Or other suitable ballistic laminates under consolidation by isostatic pressing. The resin compound layer may be a layer in the stack, if necessary. When the side walls are protected, the pressure acting on the remaining surface of the laminate provides compression for extruding the laminate at its side walls, which acts to subsequently tension the reinforcing fibres. The resulting laminate is thinner and slightly elongated in its major dimension while maintaining the same volume. This tightening of the reinforcing fibers has a beneficial effect on the penetration resistance of the resulting laminate, where excellent performance results when combined with a relatively low Standard Deviation (SD) associated with ballistic test results for isostatic bonded laminates.

Isostatic side pressure protection (ISPS) composite consolidation according to one embodiment of the invention includes a fixture that protects the sidewalls of the laminate from pressure while exposing the laminate and fixture together to isostatic pressure.

Preferably, the securing means comprises a circumferential side wall portion and provides pressure protection of the laminate side wall, a closed profile portion controlling the curvature of the laminate, and a sealing portion. The circumferential side wall portion may take any such shape as desired.

Preferably, the sealed portion contains an opening that allows the application of isostatic pressure directly to all portions except the periphery of the laminate surface with which it contacts.

Preferably, the closed profile portion and the sealing portion both contact the circumferential portion and the non-sidewall laminate surface and form a sealing void between the circumferential portion and the sidewall of the laminate. The sealing portion and the closed profile portion are movable towards each other under pressure and preferably the opposing surfaces of the sealing portion and the closed profile portion are an offset of the same profile, the offset being determined by the thickness of the laminate.

In various embodiments of the invention, the circumferential portion and the closed profile portion may be combined, or the circumferential portion and the sealing portion may be combined.

In operation, the laminate and the fixture are typically enclosed in a reusable silicone membrane and heat sealed in a disposable plastic bag, fused under vacuum with the contents and surroundings. The silicone septum may comprise a plurality of separate portions and is desirably pre-formed to precisely fit the laminate and the fixture. The silicone membrane is sufficiently flexible to transmit the applied pressure to the exposed laminate and the surface of the fixture without significant loss of isostatic pressure properties. XTclave at XTEKLimited is desirable^TMDuring composite consolidation, the heat sealed disposable plastic bag containing the silicone membrane, the fixture and laminate is simultaneously and controllably cycled through ISPS consolidation of the laminate by applying elevated isostatic pressure and temperature. The laminate is then extracted from the heat-sealed disposable plastic bag, the silicone septum and the fixture and typically finished.

Preferably, the circumferential portion, the closed profile portion and the sealing portion are constructed of a rigid and strong material, such as a metal, metal alloy or composite material. Further preferably, these materials should have an advantageous thermal conductivity. Various successful embodiments of the present invention have used steel alloys (AS1444-1996 + 4140), aluminum alloys (ASTM B2096061-T6), and carbon fiber reinforced epoxy matrices (GMSComposites EP-250) designed for high temperature composite processing applications. It has been found advantageous to use a lubricant, such as a lithium-based grease comprising molybdenum disulphide, to assist the movement between the sealing portion and the circumferential portion.

Preferably, the circumferential side wall portion is non-circular.

Preferably, the application of pressure to the fixture acts to close the interface between the circumferential portion and the sealing and closure profile portions. Further preferably, the sealing portion is designed to elastically deform under pressure to maintain contact with the circumferential portion. The use of applied pressure to activate the sealing action can improve functionality and reliability.

For subjecting the laminate undergoing ISPS composite consolidation to flow, it is advantageous to position the membrane between the seal portion and the laminate. Preferably, the film extends over the entire surface of the laminate. Such a membrane serves to minimize marking of the laminate at the periphery of its interface with the sealing portion. Various successful embodiments of the present invention have used thin (0.2mm) brass (Alloy C26000) and polycarbonate (0.5mm) materials for such membranes. Most importantly, such membranes must be flexible enough to transmit the applied pressure to the exposed laminate without significant loss of isostatic characteristics.

In another form of the invention, there is a mold for a ballistic article by consolidating a laminate stack, the mold comprising:

a sliding seal portion; and

a base profile portion having a circumferentially upwardly extending sidewall having an inner surface and a base profile surface;

the circumferentially upwardly extending side wall has an inner dimension greater than an outer dimension of the laminated stack to be consolidated;

wherein the sliding seal portion forms a sliding fit with an inner surface of the circumferentially extending sidewall.

Preferably, the sealing portion protects the sides of the laminated stack from external pressure.

Preferably, the inner dimension of the circumferentially upwardly extending side wall of the base profile portion is 0.001mm to 25mm greater than the outer dimension of the laminate stack to be consolidated.

Preferably, the sealing portion is a ring or a band.

Preferably, the sliding seal portion is a ring or band having an angled profile.

Preferably, the sliding seal portion is a ring or a band having an inclined profile.

Preferably, the sliding seal portion is a ring or band having an "L" shaped profile.

Preferably, the sealing portion is a hoop or a band having a substantially uniform profile.

Preferably, the sealing portion is deformable.

Preferably, the base-shaped face portion is of two pieces.

Preferably, the base profile portion is two-piece, comprising a base profile portion and a circumferential side wall portion.

Preferably, the mould is a moulding tool.

In another form of the present invention, there is provided a method of making a molded article comprising the steps of: forming a stack of laminates;

providing an isostatic pressing device;

placing the stack of laminates in a mold, the mold having a sliding seal portion; and

a base profile portion having a circumferentially upwardly extending sidewall having an inner surface and a base profile surface;

the circumferentially upwardly extending sidewalls of the base profile portion have an inner dimension greater than an outer dimension of the laminate stack to be consolidated;

an isostatic pressure is applied to the outer surface of the sliding seal ring,

wherein the sliding seal portion forms a sliding fit under isostatic pressure with an inner surface of the circumferentially extending sidewall.

Preferably, the molded article is a ballistic article.

Preferably, the sealing portion is deformable.

Preferably, the stack of laminates has a top face, a bottom face and side faces.

Preferably, isostatic pressure is prevented from being applied to the sides of the laminate.

Drawings

Embodiments of the present invention will now be described, by way of example/illustration only, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a first embodiment of the present invention;

FIG. 2 is an exploded perspective view of the embodiment shown in FIG. 1;

FIG. 3A is a perspective cross-sectional view taken along A-A of FIG. 1, wherein the stack is not laminated;

FIG. 3B is a perspective cross-sectional view taken along A-A of FIG. 1 with a laminate stack;

FIG. 4 is a partial cross-sectional view of a side portion of the present invention with a laminate stack therein;

figure 5 is a partial cross-sectional view of a second embodiment of the invention having a laminate stack;

figure 6 is a partial cross-sectional view of a third embodiment of the invention having a laminate stack; and

figure 7 is a partial cross-sectional view of a fourth embodiment of the present invention having a laminate stack.

Detailed Description

The term "laminated stack" as used herein refers to a stack of materials such as ballistic materials or ballistic laminates that are stacked on top of one another to form a stack or stack.

The term "prepreg" as used herein refers to a fabric material that has been pre-impregnated with a resin system or matrix, such as ballistic material of ballistic laminates.

Referring to fig. 1, there is shown a composite consolidation apparatus or mold (100) of the present invention, in which the circumferential portion (1) fits closely over the upwardly extending base profile (39) with a close fit between the surfaces (40) and (36) of the circumferential portion when assembled. The laminate stack (4) is then placed within the opening (37), wherein the laminate stack (4) is smaller in size than the opening such that between the side (41) of the laminate stack (4) of prepreg material and the inner surface (36) of the circumferential portion (1) is between 0mm and 25 mm. For example, fig. 4 shows that the gap between the inner surface (36) of the circumferential portion (1) and the side surface (41) of the laminate stack (4) is > 0 mm.

The sealing portion (3) is then tightly fitted in the opening (37) of the circumferential portion (1) and is a sliding fit between the outer surface (28) of the sealing portion (3) and the inner surface (36) of the circumferential portion (1). This tight fit between the sealing portion (3) and the circumferential portion (1) can be seen in fig. 3 and 4.

Referring to fig. 2, the mold apparatus (100) includes a sealing portion (3), a circumferential portion (1), and a profile portion (base portion) (2). The sealing portion (3) is shaped to form a sliding fit within the circumferential portion (1) which is then shaped to fit with a portion of the profile portion (base portion) (2).

The sealing portion (3) has an outer surface (28), an inner surface (31), a top edge (29), a bottom edge (30), and an opening (34). The inner surface (31) has inclined ramps (32) and (33) to provide a substantially uniform profile around the hoop or band, which in this embodiment is an inclined or angled profile, but could also be an "L" shaped profile, as shown in figures 5 and 7. The outer surface (28) is shaped to match the inner surface (36) of the circumferential portion (1) to provide a tight sliding fit when the sealing portion (3) is inserted into the circumferential portion (1). The sealing portion (3) may be made of a deformable material such that any pressure applied to the sealing portion (3) may create an activated seal between itself and the inner surface (36) of the circumferential portion (1).

The circumferential portion (1) comprises an outer surface (35) and an inner surface (36) parallel to each other. The opening (37) is of a shape that matches the outer surface (28) of the sealing portion (3) to allow the sealing portion (3) to be inserted into the opening.

The profile portion (base) (2) has a flange portion (38) at its periphery such that the circumferential portion (1) can be placed directly on the flange surface (38) such that a portion of the inner surface (36) abuts the surface (40) of the profile portion (2) or is adjacent to the surface (40) of the profile portion (2) with a close fit. The surface (39) of the profile portion (base) (2) supports the surface shape of the ballistic article to be manufactured. The surface (39) may be smooth or patterned as desired. As shown in fig. 5, the surface (39) is slightly concave to form a curved ballistic article. Other shapes are considered to fall within the scope of the present invention.

A cross-section of the composite consolidation apparatus or mold (100) taken along line a-a of fig. 1 is shown in fig. 3A. The composite consolidation apparatus or mold (100) in fig. 3A is devoid of any lamination stack and shows the arrangement of the circumferential portion (1) with the sealing portion (3) slidingly inserted such that it nests against the inner surface (36). Fig. 3B is the same view as fig. 3A, with a lamination stack (4) in it. The laminate stack (4) has a top or upper surface (54), a bottom surface (55) and side surfaces (41). When the circumferential portion (1) and the profile portion (base) (2) are brought together, the laminate stack (4) is placed in the opening (37) of the circumferential portion (1) such that the bottom face (55) of the laminate stack (4) rests on the surface (39) of the profile portion (base) (2).

Then, the seal portion (3) is inserted into the opening (37) of the circumferential portion (1), and a part of the upper surface (54) of the lamination stack body (4) is exposed. The inner diameter of the opening (37) of the circumferential portion (1) is equal to or larger than the outer diameter of the laminated stack (4). When the outer diameter of the laminated stack (4) is smaller than the inner diameter of the opening (37) of the circumferential portion (1), a sealed void (5) is formed.

The assembled composite consolidation apparatus or mold (100) with the laminate stack (4) placed thereon is then inserted into a flexible silicone membrane (6), sealed under vacuum and inserted into a protective plastic bag (7), and then placed into a suitable consolidation apparatus such as an autoclave at high pressure, the final pressure applied may then apply isostatic pressure to the top surface (54) of the laminate stack (4) and the inclined bevel (31) of the sealing portion (3), thus providing isostatic side pressure protection to the side surfaces (41) of the laminate stack (4). In this way, in the consolidated state (pressure and heat), excess matrix (resin) material is forced to the sides (41) of the laminate stack (4) and into the sealed voids (5), thereby preventing isostatic pressure from being applied to the sides (41) of the laminate stack (4) through the consolidated state.

Referring to fig. 4, which shows a partial cross-sectional view of an isostatic composite consolidation apparatus or mould (100) of the invention, there is shown a fixture or composite consolidation apparatus or mould comprising a circumferential portion (1), a closed profile portion (2) and a sealing portion (3), comprising a laminate stack (4). The sealed void (5) is evident. The fixation means are housed in a two-part silicone septum (6) housed in a sealed plastic bag (7). This form of the invention is modular in that it allows the use of an alternative form of closed profile portion (2) required in consolidating laminated stacks of different thicknesses.

Fig. 5 is a partial cross-sectional view of a second embodiment of the invention showing a fixture comprising a circumferential section in combination with a closed profile section (8) and a sealing section (9) comprising a laminate stack (10). The sealed void (11) is evident. The fixation means are housed in a silicone septum (12) housed inside a sealed plastic bag (13). Such an embodiment of the invention is compact, particularly for the thickness of the laminated stack, although not modular.

Fig. 6 is a partial cross-sectional view of a third embodiment of the invention showing a fixture comprising a circumferential section in combination with a sealing section (14) of L-shaped profile and a closed profile section (15) containing a laminate stack (16). The sealed void (17) is evident. An additional sealing ring (18) made of a suitable sealing material (e.g., rubber or other deformable material) is positioned on the back of the closed profile portion (15) to form a secure seal between the closed profile portion (15) and the L-profile sealing portion (14). The fixation means are housed in a two-part silicone septum (19) housed within a sealed plastic bag (20). This form of the invention is compact and modular.

Fig. 7 is a partial cross-sectional view of a fourth embodiment of the invention showing a fixture comprising a circumferential section in combination with a closed profile section (21) and a sealing section (22) comprising a laminate stack (23). A flat sealing film (24) is positioned between the sealing portion (22) and the lamination stack (23) to produce a sealing action between the sealing portion (22) and the lamination stack (23). A flat sealing film (24) may be used in combination with any form of the disclosed invention to enhance the sealing action between the laminate stack and any adjacent sealing surface. The sealed void (25) is evident. The fixing means are housed in a silicone septum (26) housed inside a sealed plastic bag (27). This embodiment of the invention employs an additional membrane (24) to minimize marking of the laminate stack (23) at its perimeter at the interface with the seal portion (22).

Ballistic articles formed by the present invention are shown to have significantly improved ballistic performance by allowing excess prepreg matrix material to be extruded from the body of the laminate stack as compared to similar ballistic articles produced by known isostatic pressing methods and apparatus. In addition, the ballistic articles formed by the present invention are also thinner and lighter than ballistic articles made by other isostatic pressing processes, thus providing a significant improvement over known ballistic articles.