GB2333738A

GB2333738A - Compression moulding a laminated article

Info

Publication number: GB2333738A
Application number: GB9902306A
Authority: GB
Inventors: James Purves
Original assignee: PLASTECHNOL Ltd
Current assignee: PLASTECHNOL Ltd
Priority date: 1998-02-02
Filing date: 1999-02-02
Publication date: 1999-08-04
Also published as: GB9802232D0; GB9902306D0

Abstract

A multi-layer article comprising a complex shaped stack of reinforced plastic layers is formed by compression moulding, the layers being fastened to one another prior to the application of pressure in the moulding process, so that lateral displacement of the layers is prevented. A stack of layers of material is impregnated with a thermosetting resin, and after the fastening together of the layers, the resin is cured by heating whilst the pressure is applied to urge the layers towards one another and compress the stack. Preferably, layers of dry glass cloth are layered in a mould cavity, the layers having been stitched together to produce a multi-layer laminate which fills the mould cavity, liquid thermosetting resin is injected, preferably under pressure, into the closed mould cavity, and finally heat and pressure are applied to cure the liquid thermosetting resin. This method may be used to produce a complex shaped article of variable thickness. The method is particularly suited to the manufacture of security panelling 11 for providing bullet-proof protection in premises which handle valuable items such as cash, since the method allows the formation of complex shaped articles without detracting from their ballistic performance. It may also be used in the manufacture of land, marine or air vehicles.

Description

STRUCTURE AND A NETHOD OF ITS MANUFACTURE This invention relates to structure comprising a layer of fibre reinforced plastics material,the fibres of the layer being in the form of a compressed stack. More particularly, although not exclusively, the compressed stack of fibres comprises a stack of layers of woven glass cloth. Structure to which this invention relates has an application in security panelling for providing protection against shell fragments, glass, bullets, and any other projectiles, for high security areas in commercial or industrial premises such as accounts departments and offices which handle cash. Such security panelling may be installed to protect walls, doors and counter areas.

Structure to which this invention relates may also be used in land, marine or air vehicles.

-Up to now, security panelling which incorporates protective structure of the kind to which this invention relates has been an assembly of flat panels. The protective structure which comprises a layer of fibre reinforced plastics material in the form of a compressed stack has been made by laying up a few layers of dry woven fibre material, pouring thermosetting resin onto those layers so that the resin impregnates those layers, laying a few more layers of dry woven fibre material onto the resin impregnated layers, pouring more thermosetting resin onto those further layers and so on until the required number of layers have been laid up and thermosetting resin poured onto them to impregnate them, the resultant stack of resin impregnated layers of woven fibre material was then compressed in a press whilst being heated to cure the resultant compressed resin impregnated laminate to form a flat panel of the protective structure. Attempts to form curved panels by a similar technique which included laying up layers of woven fibre in a suitable mould having an appropriately curved surface, impregnating those layers of woven fibre with thermosetting resin and then compressing the resin impregnated layers laid up on the curved surface while applying heat and pressure to cure the resin have been unsatisfactory because the ballistic performance of the resultant curved panel was found to be inferior to that of the flat panels described above.

An object of this invention is to provide curved structure which is suitable for use in security panelling which has equivalent ballistic performance to the known flat panels. Another object of this invention is to provide curved structure which is suitable for use as structure of a vehicle body part and which has an improved impact strength in such an application.

According to this invention there is provided a method of forming structure comprising a layer of fibre reinforced plastics material in the form of a compressed stack having a complex shape, in which a stack of layers of fibre material is impregnated with a thermosetting resin and the resin is cured by heating whilst pressure is applied to urge the layers towards one another and compress the stack, wherein the layers are fastened to one another before pressure is applied to compress the stack whereby juxtaposed layers are held against relative lateral displacement during curing of the resin under pressure.

Preferably, the layers of fibre material are laid up to fill a mould cavity which has the form of the structure of complex shape and are impregnated with the resin in that mould cavity. The preferred form of each layer of fibre material is a woven fibre material. In a preferred method which embodies this invention, the thermosetting resin by which the stack of fibre material is impregnated in the mould cavity is injected into the mould cavity under pressure such that the pressure to which the resin impregnated stack is subjected during curing of the resin is a combination of the pressure that is applied in the mould cavity to compress the stack and the pressure of the resin that has been injected into the mould cavity under pressure. Conveniently the layers are fastened to one another by stitching.

The layers are preferably fastened to one another before being placed in the mould cavity. The fastening may be such that the volume of the resultant stack of layers that have been fastened together is less than would be the volume of a similar stack of similar layers simply laid one of top of another. The layers that are laid up in the mould cavity to fill it may be arranged in more than one stack of such layers which have been fastened together, such stacks being laid up on one another.

The thickness of the resultant structure may be varied between one part and another to suit the design requirements.

Two alternate forms of security panelling including protective structure which embodies this invention, the security panelling being in a complex shape and being fitted on to a front and top of a cashiers counter will be described now by way of example with reference to the accompanying drawings, of which Figure 1 is a view in perspective of a fragment, including one end, of a straight portion of a cashiers' counter fitted with one of the forms of security panelling; Figure 2 is an illustration of a fragmentary portion II of the security panelling shown in Figure 1, drawn to a larger scale than in Figure 1; and Figure 3 is an end view of a cashiers' counter fitted with the other form of security panelling.

Figure 1 shows a cashiers' counter (10) having a basic rectangular structure. Protective structure (11) having a complex shape is fitted to the top and front of the counter (10) as shown in Figure 1. The protective structure (11) is a one-piece moulding comprising a flat top portion (12), a projecting front upper portion (13) and a flat lower front portion (14). The top portion (12) is laid on the top of the counter (10) and projects from the front of the counter (10) to form the top of the projecting front upper portion (13). The latter is angled, comprising an upper portion which depends from the front edge of the top portion (12) and an oblique portion which slopes downwardly and towards the front of the counter (10). The lower front portion (14) depends from the lower edge of the angled projecting front portion (13) and lines the lower portion of the front of the counter (10).

The protective structure (11) was formed as a one piece moulding in a two-part injection mould which forms a closed mould cavity provided with injection apparatus operable to inject liquid thermosetting resin into the closed mould cavity. Layers of dry glass cloth were laid up in the mould cavity before any liquid thermosetting resin was injected into the mould cavity. When so laid up, the layers of glass cloth form a multi-layer laminate. The layers of that multi-layer laminate were then stitched together. The stitching was such that the volume of the resultant stack of layers that had been stitched together was less than the volume of a similar stack of similar layers similarly laid one on top of another without being stitched together. The resultant stack of layers stitched together substantially filled the mould cavity. Once the mould cavity had been filled with the stack of layers of glass cloth that were stitched together, the mould was closed and liquid thermosetting resin was injected into the mould so as to impregnate the stack of layers of glass cloth. The resin impregnated stack within the mould cavity was then subjected to pressure which was the combined effect of the pressure at which the resin was injected into the mould cavity and pressure applied by the closing movement of the two parts of the mould which were moved one relative to the other. Heat was applied at the same time to cure the resin.

Figure 3 shows another form of protective structure (ill) for a cashiers' counter. The protective structure shown in Figure 3 differs from that shown in Figure 1 in the form of the projecting front portion (13A). Although the latter is angled and has an upper portion which depends from the front edge of the top portion (12A), as does that of the structure (11) shown in Figure 1, the remainder is substantially normal to the depending upper portion and the lower front portion (14A) rather than being oblique as in Figure 1.

Claims

1. A method of forming structure comprising a layer of fiber reinforced plastics material in the form of a compressed stack having a complex shape, in which a stack of layers of fiber material is impregnated with a thermosetting resin and the resin is cured by heating whilst pressure is applied to urge the layers towards one another and compress the stack, wherein the layers are fastened to one another before pressure is applied to compress the stack whereby juxtaposed layers are held against relative lateral displacement during curing of the resin under pressure.

2. A method according to claim 1, wherein each layer of material is woven fiber material.

3. A method according to claim 1 or claim 2, wherein the layers of fiber material are laid up to fill a mould cavity which has the form of the structure of complex shape and are impregnated with the resin in that mould cavity.

4. A method according to claim 3, wherein the thermosetting resin by which the stack of fiber material is impregnated in the mould cavity is injected into the mould cavity under pressure such that the pressure to which the resin impregnated stack is subjected during curing of the resin is a combination of the pressure that is applied in the mould cavity to compress the stack and the pressure of the resin that has been injected into the mould cavity under pressure.

5. A method according to any one of claims 1 to 4, wherein the layers are fastened to one another by stitching.

6. A method according to any one of claims 3 to 5, wherein the layers are fastened to one another before being placed in the mould cavity.

7. A method according to any one of claims 1 to 6, wherein the fastening is such that the volume of the resultant stack of layers that have been fastened together is less than would be the volume of a similar stack of similar layers simply laid one on top of another.

8. A method according to any one of claims 3 to 6, or to claim 7, when appended to claim 3, wherein the layers laid up in the mould cavity are arranged in more than one stack of such layers which have been fastened together,. such stacks being laid up on one another.

9. A method according to any one of claims 1 to 8, wherein the thickness of the resultant structure is varied between one part and another.

10. A method of forming protective structure substantially as described hereinbefore with reference to the accompanying drawings.