Isostatic side-pressure shielded composite consolidation

Abstract

A mold for use in the production of a ballistic article from a composite laminate stacked material wherein the mold has a sliding sealing section that nests with a outer permitter section and base portion so as to shield the sides of the composite laminate stacked material from applied isostatic pressure applied when in an autoclave. By shielding the sides of the composite laminate stacked material excess resin matrix material can be forced from the composite laminate stacked material to provide a uniform composite article with reduced weight and reduced thickness.

Claims

1. A process for the preparation of a molded article including the steps of: forming a stack of laminate material; providing an isostatic pressurizing means; placing the stack of laminate material in a mold, the mold having a sliding sealing section, and a base profile section having a circumferential upwardly extending side wall with an inner face and a base profile surface; the circumferential upwardly extending side wall of the base profile section having an internal dimension that is greater than an outer dimension of the laminate stack to be consolidated; placing the mold into a flexible membrane; placing the mold in a plastic bag and sealing; applying an isostatic pressure to the external surfaces of the sliding sealing section; wherein the sliding sealing section forms a sliding fit with the inner face of the circumferential upwardly extending side wall under the isostatic pressure.

2. The isostatic composite consolidation process of claim 1, wherein the sliding sealing section is deformable.

3. The isostatic composite consolidation process of claim 1, wherein the stack of laminate material has a top surface, bottom surface and a side surface, and wherein a sealed void is formed between the circumferential upwardly extending side wall of the base profile section and the side surface of the stack of laminate material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) By way of example/illustration only, an embodiment of the invention is described with reference to the accompanying figures, in which:

(2) FIG. 1. is a perspective view of a first embodiment of the invention;

(3) FIG. 2 is a perspective exploded view of the embodiment shown in FIG. 1;

(4) FIG. 3A is a perspective cross sectional view of FIG. 1 along A-A, without a laminate stack in place;

(5) FIG. 3B is a perspective cross sectional view of FIG. 1 along A-A, with a laminate stack in place;

(6) FIG. 4 is a partial sectioned view of a side section of the present invention with a laminate stack in place;

(7) FIG. 5 is a partial sectioned view of a second embodiment of the invention with a laminate stack in place;

(8) FIG. 6 is a partial sectioned view of a third embodiment of the invention with a laminate stack in place;

(9) FIG. 7 is a partial sectioned view of a fourth embodiment of the invention with a laminate stack in place.

DESCRIPTION

(10) The term laminate stack as used herein refers to a stack of material, such as ballistic material or ballistic laminate sheets layered on top of each other so as to form a pile or stack.

(11) The term prepreg as used herein refers to fabric material, such as ballistic material of ballistic laminate sheets, that have been pre-impregnated with a resin system or matrix.

(12) With reference to FIG. 1, there is shown a composite consolidation apparatus or mold (100) of the present invention when assembled, the circumferential section (1) fits snugly over the upwardly extending base profile surface (39), there being a tight fit between the faces (40) and (36) of the circumferential section. A laminate stack (4) is then placed within the opening (37), with the size of the laminate stack (4) being less than the opening so that there is between 0 mm and 25 mm between a lateral side (41) of a laminate stack of prepreg material (4) and the inner surface (36) of the circumferential section (1). FIG. 4, for example, shows a gap of >0 mm between the inner face (36) of the circumferential section (1) and the lateral side face (41) of the laminate stack (4).

(13) The sealing section (3) then fits snugly into the opening (37) of the circumferential section (1), with a sliding fit between the outer face (28) of the sealing section (3) and the inner face (36) of the circumferential section (1). This close fitting between the sealing section (3) and the circumferential section (1) can be seen in FIGS. 3 and 4.

(14) Referring to FIG. 2, being, the mold apparatus (100) includes a sealing section (3), a circumferential section (1) and a profile section (base section) (2). The sealing section (3) is shaped so as to form a sliding fit within the circumferential section (1), which in turn is shaped to mate with a portion of the profile section (base section) (2).

(15) The sealing section (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 bevelled sloping faces (32) and (33), to provide a substantially constant profile about the hoop or band, which in this embodiment is a bevelled or angled profile but may also be an L-shaped profile as shown in FIGS. 5 and 7. The outer surface (28) is shaped to match an inner surface (36) of the circumferential section (1) so as to provide a tight sliding fit when the sealing section (3) is inserted into the circumferential section (1). The sealing section (3) can be made from a deformable material, such that any pressure applied to the sealing section (3) can generate an energized seal between itself and the inner surface (36) of the circumferential section (1).

(16) The circumferential section (1) includes an outer surface (35) and an inner surface (36), both being parallel to one another. The opening (37) is of a matching shape to the outer surface (28) of the sealing section (3) so as to allow the sealing section (3) to be inserted therein.

(17) The profile section (base section) (2) has a flange section (38) about its periphery so that the circumferential section (1) can be placed directly on the flange surface (38) so that a portion of the inner face (36) abuts, or is contiguous with, the face (40) of the profile section (2) with a tight fit. The surface (39) of the profile section (base section) (2) carries the shape of a face of the ballistic article that is to be produced. The surface (39) may be smooth or patterned as required. As shown in FIG. 5, the surface (39) is slightly concave so as to create a curved ballistic article. Other shapes are considered to fall within the scope of the present invention.

(18) A cross section of the composite consolidation apparatus or mold (100) is shown in FIG. 3A, which is along the lines A-A from FIG. 1. The composite consolidation apparatus or mold (100) in FIG. 3A does not have any laminate stack in place and shows the arrangement of the circumferential section (1) with the sealing section (3) slidingly inserted so that it nests up against the inner surface (36). FIG. 3B is the same view as FIG. 3A with a laminate stack (4) in place. The laminate stack (4) has a top or upper surface (54), a bottom surface (55) and side surfaces (41). When the circumferential section (1) and profile section (base section) (2) are placed together the laminate stack (4) is placed into the opening (37) of the circumferential section (1) so that the bottom face (55) of the laminate stack (4) rests against the surface (39) of the profile section (base section) (2).

(19) The sealing section (3) is then inserted into the opening (37) of the circumferential section (1) and a portion of the upper surface (54) of the laminate stack (4) is left exposed. The inner diameter of the opening (37) of the circumferential section (1) is equal to or greater than an outer diameter of the laminate stack (4). When the outer diameter of the laminate stack (4) is less than the inner diameter of the opening (37) of the circumferential section (1) a sealed void (5) is formed.

(20) The assembled composite consolidation apparatus or mold (100) with laminate stack (4) in place is then inserted into a flexible silicone membrane (6), sealed under vacuum and into a protective plastic bag (7) and then placed into a suitable consolidation apparatus such as a high pressure autoclave, the resulting pressure applied can then exert isostatic pressure to the top surface (54) of the laminate stack (4) as well as against the bevelled sloping surface (31) of the sealing section (3) thus providing isostatic side-pressure shielding to the sides (41) of the laminate stack (4). As such, under consolidation conditions (pressure and heat) excess matrix (resin) material is forced to the sides (41) of the laminate stack (4) and into the sealed void (5), isostatic pressure thus prevented from being applied by the consolidation conditions to the sides (41) of the laminate stack (4).

(21) Referring to FIG. 4, this shows a partial sectioned view isostatic composite consolidation apparatus or mold (100) of the present invention, showing the fixture or composite consolidation apparatus or mold, comprised of the circumferential section (1), enclosing profiled section (2) and sealing section (3), containing the laminate stack (4). The sealed void (5) is evident. The fixture is contained within a two-part silicone membrane (6) that is contained within a sealed plastic bag (7). This form of the invention is modular in that it allows for alternate versions of the enclosing profiled section (2) to be employed; necessary when consolidating laminate stacks of varied thickness.

(22) FIG. 5 is a partial sectioned view of a second embodiment of the invention, showing the fixture, comprised of the circumferential section combined with the enclosing profiled section (8) and sealing section (9), containing the laminate stack (10). The sealed void (11) is evident. The fixture is contained within a silicone membrane (12) that is contained within a sealed plastic bag (13). This embodiment of the invention is compact although not modular; being specific to a laminate stack thickness.

(23) FIG. 6 is a partial sectioned view of a third embodiment of the invention, showing the fixture, comprised of the circumferential section combined with the L-shaped profile sealing section (14) and enclosing profiled section (15), containing the laminate stack (16). The sealed void (17) is evident. An additional sealing ring (18), made from a suitable sealing material such as rubber or other deformable material, is positioned on a rear face of the enclosing profiled section (15) so as to create a firm seal between the enclosing profiled section (15) and the L-shaped profile sealing section (14). The fixture is contained within a two-part silicone membrane (19) that is contained within a sealed plastic bag (20). This form of the invention is compact and modular.

(24) FIG. 7 is a partial sectioned view of a fourth embodiment of the invention, showing the fixture, comprised of the circumferential section combined with the enclosing profiled section (21) and sealing section (22), containing the laminate stack (23). A planar sealing membrane (24) is positioned between the sealing section (22) and the laminate stack (23) to create a sealing effect between sealing section (22) and the laminate stack (23). The planar sealing membrane (24) can be used in conjunction with any of the forms of the present invention as disclosed so as to enhance said selling effect between the laminate stack and any adjacent sealing surface. The sealed void (25) is evident. The fixture is contained within a silicone membrane (26) that is contained within a sealed plastic bag (27). This embodiment of the invention employs an additional membrane (24) to minimise marking of the laminate stack (23) at the perimeter of its interface with the sealing section (22).

(25) The ballistic articles formed by the present invention have been shown to have significantly improved ballistic resistance compared to similar ballistic articles produced by known isostatic pressure processes and equipment by allowing excess prepreg matrix material to be forced out of the main body of the laminate stack. In addition, the ballistic articles formed by the present invention are also thinner and lighter than those produced by other isostatic processes, thus providing a significant improvement over that which is already known.