Structures"

This invention aims to Drovide means whereby a one niece reinforced structure may be formed so as to have at least some oortions which are substantially rigid whilst other portions may be of a flexible nature, if desired.

According to the present invention there is provided a nethod of forcing a one-piece structure, wherein fibres are laid within aπ open mould under controlled tension, the voids between the fibres are filled with a compatible settable resin, a closure portion for the mould is pressed down onto the mould to compress selectively parts of the formed structure so that the fibres in those arts are forced into the reαuired shape and reduced thickness whilst excess resin is expelled or forced into void areas within the mould, thus providing required fibre content and tension, and the resin is then allowed to cure.

The method may be employed so as to create a structure incorporating a mixture of substantially rigid and of flexible portions. Thus by using this method oarts of the structure can be formed with reduced thickness, while the fibres are placed under greater tension, so as to achieve a reasonable degree of

flexibility, while other parts of the structure will be substantially rigid. This allows for the construction of such items as a one-piece vehicle chassis to incorpo¬ rate flexible wheel support limbs and, if desired, impact absorbing portions. In a preferred arrangement parts of the mould, other than those where selective compression is to take place, are formed to have a width dimension between the side walls cor.Darable to the thickness dimension to be formed between the upper and lower walls for the reduced thickness parts of the structure. Bv this means the narrow width narts o the structure will be flexible in one direction whilst those parts which have been reduced in thickness, accompanied by compressing of the fibres, will be flexible in other directions.

Ideally the fibres will be laid around σosts posi¬ tioned wit,hin the open mould, with the closure oortion incorporating parts for compressing fibres in the axial direction of the posts. In one form of construc ion, at least some of the posts oro ect above the top wall of the open mould, and fibres are laid around the arts of the oost within the open mould and projecting therefrom. In this instance the closure portion can incorporate openings to receive the projecting oarts of the posts as the mould is closed. Alternatively, the posts could be formed with large heads and could be slidablv received

within the open mould, and the closure portion is designed to force the posts down through passageways in the open mould as the mould is closed.

The resin may be introduced either by p e-in regna- 5 tiσn of the fibres with a controlled amount of the resin, or bythe resin being poured or injected into the mould after laying down of the fibres.

The compression of the material in the mould may be achieved by forcing the two mould parts together or by 0 vacuum assisted press moulding or other conventional techniques.

From a further aspect the invention extends to a mould comprising an open mould portion and a closure portion for use in the method of this invention as χ-j hereinbefore defined.

The invention also extends to a one piece structure incorporating rigid portions or a mixture of rigid and flexible portions as formed by a method of this invention as hereinbefore defined. In particular the 20 invention may relate to a one piece structure formed from fibres embedded in a cured compatible resin, wherein parts thereof are formed to have a significantly lesser thickness than others, with the fibres in those parts being constrained under greater tension than 25 elsewhere, so that those parts are flexible in nature whilst other parts of the structure are relatively rigid.

The invention may be performed in various ways and preferred embodiments thereof will now be described with reference to the accompanying drawings, in which:-

Figures 1 and 2 comprise side and perspective views - respectivelv of upper and lower mould portions of a mould of this invention; figures 3 to 5 comprise vertical sections through alternative forms of upper and lower mould portions of a mould of this invention; *-® Figures δ and ^*7 are perspective views of one piece structures formed by using a method of this invention; and

Figures P. and 9 are plan and side views respectively of parts of another example of a mould of this invention. - ^■ - The ooen mould portion 1 illustrated in Figures 1 and ° is formed with channels 2 within which are laid fibres under ^' controlled tension. The fibres are passed throughout all portions of the channel 2 and are positioned about posts 3 within the channels 2, at - ~ strategic points. *■*. suitable resin is then poured into the open mould 1 to impregnate the fibres. A closure portion 4 (Figures 1, 3 and 4) for the mould is then laid on top of the open mould 1 so that the posts 3 pass through openings 5 within the closure portion 4. As

^* '_? ^• *-^ the mould is closed the fibres wound around the posts 3 are compressed downwardly into the open mould 1 and the

resin 6 is also compressed. Excess resin and air will escape through the joint line or breather holes (not shown). The resin is then cured (possibly using heat) and the mould is opened so that the formed component can 5 be extracted.

In the arrangement shown in Figure 4 the fibres will be wound around portions of the posts 3 which project above the top surface of the open mould 1. T7hen the closure member 4 is pressed into place the compressing IP of the fibres will result in the resin 6 being forced upwardly to fill the space 7 within the closure portion 4. In a further arrangement shown in Figure 5 the posts 3 are slicable within the open mould 1 and incorporate mushroom-s aped heads 8 to restrain the fibres. -***.s the 15 ^• closure member 4 is pressed down into the open mould 1 the closure portion also presses down on the head 8 of each post 3 so that the fibres are compressed.

In certain regions of the mould no downward com¬ pression of the fibres will be created as the mould is 20 closed. However, some such parts of the mould may be of a relatively narrow width so that thin vertical sections of the final structure with embedded fibres, will be created.

Two possible structures which can be formed using

25 the types of mould shown in Figures 1 to 5 of the drawings, are illustrated in Figures 6 and 7. In

"igure 6 there is shown a complete chassis member for a vehicle. This structural component has relatively rigid portions combined with flexible parts, particular¬ ly wishbone-type wheel support struts 9. These are of relatively narrow deoth and are formed by compression of the resin and fibres as parts of the mould are closed together. Front, rear and side impact absorbing por¬ tions 10, 11 and 12 are created by forming these parts of relatively narrow width, but without any significant vertical compression as the mould is closed. A diff¬ erent form of chassis member is illustrated in Figure 7. This has a substantial rigid frame formed bv portions 13 and 14 combined with flexible arm portions 15 which are created by flattening and compression of the resin and fibres as the mould is closed. Fixing points 16 and 17 can readily be incorporated into the structure. The posts 3 within the mould can there ore form, the dua. ¹ function of supporting the fibres during the forming process and creating openings through the structure to create the fixing points.

In the embodiment shown in Figures 3 and 9 continuous fibres 17 are wound about pins 1° carried on supports 19. Mould halves 20 are pressed about the fibres by rams 21 and resin is injected at the same time so that the space within the mould is filled, uhen the resin has cured and the mould halves are released the

upper parts 22 of the pins 13 can be removed so that the moulded item can then be taken off the pins 18. This method enables the fibres to be laid down in a relatively straightforward manner. Any convenient materials, suitable for the purpose, may be use.d to construct required items within the mould. The fibres, for example, could be formed from fibre glass, carbon fibre, flexible synthetic materials or metal wires. The resins used will be ones which are compatible with such materials.

Use of the moulding method described above with reference to the accompanying drawings results in a number of advantages. Firstly, the fibres can be forced to conform precisely to a desired shape. The tension in the fibres can be increased and compensation can be achieved for the loss of tension which results from the use of other methods. This procedure determines accu¬ rately the thickness and depth of section on each point at the component and can be used to control, within a reasonably accurate limits, the ratio of the volume of resin to fibre at any one point on the component. Furthermore, there is the possibility of using a variety of fibres either singly or in combination, such as glass, carbon, aramid, ceramic or even metal wires, introduced at selected locations to vary the physical properties of the final component. The designer of the

product can thereby select the properties he recuires to perform differing, and sometimes opposite, functions within one component, for example, stiffness in one section and flexibility and springiness in another section.