GB2500601A

GB2500601A - Press moulding apparatus and method

Info

Publication number: GB2500601A
Application number: GB1205227.0A
Authority: GB
Inventors: Daniel Thomas Jones
Original assignee: Gurit UK Ltd
Current assignee: Gurit UK Ltd
Priority date: 2012-03-26
Filing date: 2012-03-26
Publication date: 2013-10-02
Anticipated expiration: 2032-03-26
Also published as: WO2013143969A1; GB201205227D0; GB2500601B

Abstract

An apparatus for press moulding materials to form a moulded part of fibre-reinforced resin matrix composite material, the apparatus comprising a mould tool 2 defining a mould cavity 8, a recess 10 in the mould tool which is in fluid communication with the mould cavity, and a resin trap device 12 located in the recess, the resin trap device including a reservoir 14 for containing excess resin and a pressure relief valve mechanism 16 adapted to permit resin flow into the reservoir from the mould cavity when resin pressure on an outer inlet side of the valve mechanism is above a particular minimum threshold. Preferably, the reservoir and valve mechanism are a unitary piece composed of an elastomeric material and releasably located in the recess. The valve mechanism may be a one-way valve permitting only flow into the reservoir.

Description

PRESS MOULDING APPARATUS AND METHOD

The present invention relates to an apparatus for, and method of, press moulding materials including polymer resins to form a moulded part. The present invention also relates to a resin trap device for use in such an apparatus and nethod. In particular, the present invention relatcs to such an apparatus and method which are for manufacturing moulded parts composed of fibre rcinI'orced resin matrix composite materials, such as, for example, panels, more particularly automotive body panels.

It is known to produce mouldcd parts for various applications, and having various shapes and configurations, by moulding materials including polymer resins, in particular for the manufacture of moulded parts composed of fibre reinforced resin matrix composite materials.

Such composite materials are typically manufactured from moulding materials which may typically comprise, for example, (a) the combination of dry fibres and liquid resin, (b) prepregs and/or (c) sheet moulding compounds (SMC). Other materials may also be present, such as sandwich core materials and surfacing layers for forming a desired surface finish on the moulded part.

Many products are moulded by a manual process of laying-up the moulding material into a one sided mould, which moulds a single side of the resultant moulded article. Other products require a two-sided moulding process. In order to provide high manufacturing tolerance to the two-sided moulded part, it is sometimes required to use a press-moulding process in which the moulding material is moulded in a closed mould under elevated pressure.

A particular problem encountered with press moulding of an initial charge, or preform, of moulding material which at least partially comprises prepreg and/or SMC components, is that due to manufacturing tolerances in the initial charge the volume of the mould cavity is not always equal to the volume of the initial charge. Consequently, it is difficult to control the moulding process, especially to produce a composite material part having a moulded shape and dimensions which, on exit from the mould, have very close tolerance to the desired final shape and dimensions of the ultimately manufactured part, i.e. a "net shape moulded part".

This problem is particularly acute when the moulded part has fine edge details, not only because fine shape and dimensions need to be accurately moulded but also because exposed edges of the composite material must be sealed with resin, so that the fibres are not exposed, in order to avoid cosmetic or structural defects occurring during subsequent manufacturing steps or during use of the moulded part.

Currently, using known composite material moulding technology it is difficult to produce a press-inoulded net shape moulded part from a composite material which does not require to be machined, trimmed or re-worked after moulding.

The mould tool can be considered to define a fixed volumetric mould cavity. When moulding composite materials, a fibre-and resin-containing stack of moulding material, for example of prepregs or SMC, is disposed in the mould, The pressure required to consolidate the moulding material, and fully impregnate the fibre stack with resin, is created by compacting the preform. For consistent moulding the applied moulding pressure within the mould cavity needs to be maintained within a desired range.

The tooling is rigid, and accordingly a hydraulic pressure within the resin material of the moulding material is needed to achieve full impregnation of the fibres by the resin and cause resin flow to fill the geometrical details within the mould cavity, particularly at the peripheral edges of the mould cavity. Hydraulic pressure in the resin is generated by the press closing on the preform. Ideally thc press should mould a net shaped part requiring no or limited subsequent trimming, machining or rework operations.

If the part to be press-moulded has a fixed geometrical shape and dimensions, then it may be considered to have a designed fixed volume Ypart. It is desirable to produce parts in a mould cavity having a fixed volume Vcavity to simplify the press and tooling, the mould cavity being formed by an upper tool closing and mating on a lower tool. For a net shape part, this is assumed to have the designed fixed volume Ypart in the analysis below, although in practice Ycavity would be slightly higher than Vpart to allowing for machining tolerances in the mould and mould seals, In practice, prepregs are not made to a predetermined fixed volume; there are always manufacturing tolerances. Typical manufacturing tolerances for the production of prepreg are as follows: resin film casting +/-3% by weight, glass woven fabric fibre weight +1-5%, carbon woven fabric fibre weight +1-3%, machine cuffing of preform laycrs +1-1mm.

Combining all these tolerances leads to a typical possible thickness range of +1-4.0% for a carbon fibrc laminate and +1-6% for a glass fibrc laminatc stack.

When the prepreg stack is disposed in the mould and the mould is closed, clearly these manufacturing tolerances result in the initial preform volume, Vpreform, being not consistent or consistently equal to Veavity, with the result that Ycavity cannot consistently equal the final part volume \Tpart. In other words, the final press-moulded part may have an actual moulded volume Vcure which exhibits an excess volume or insufficient volume, compared to the design volume Vpart, as a result of manufacturing tolerances in the initial moulding material.

For example, one scenario for press moulding is that Vcure < Vpart. As the mould tool closcs, it contacts the preform including the fibre stack. Heat transfcr from the tool softens the resin. The heated rcshi begins to flow and impregnate the fibres, the preform starts to consolidate and reduce in volume, and the tool parts close further. Since Vcure is less than Vpart, before a significant hydraulic pressure can he generated in the resin of the prcform the matched i.ool set reaches its fixed limit to define the cavity volume Veavity. The fibre stack is not fully impregnated with resin, and in the absence of a significant hydraulic pressure, the resin does not penetrate the entire mould cavity. This causes significant moulding defects, such as dry fibres, especially in sharp geometrical details and insufficient bulk volume of all or portions of the moulded part.

Another scenario for press moulding is that Veure > Ypart. As the mould tool closes, it contacts the preform including the fibre stack. Heat ftansfer from the tool softens the resin.

The heated resin begins to flow and impregnate the fibres, the preform starts to consolidate and reduce in volume, and the tool parts close further. Since Veure is greater than Vpart, as the tool approaches is fixed limit, the hydraulic pressure in the resin rises. With only small amounts of dissolved air present, the resin can he considered to be an theompressible fluid.

Accordingly, the hydraulic pressure rises, leading to two possible consequences: (i) the upper tool does not reach its full closure position and the extra volume is compensated for by a thicker part. In reality some of this volume also ends up as resin flash which fi I Is the gap created between the mould seals and is attached to or thickens the edges of the moulded part; and/or (ii) the mould perimeter seals leak slightly, and a volume of resin escapes the mould cavity, relieving the hydraulic pressure and leading to resin flash in the mould.

Traditional solutions for press moulding of prepreg and SMC parts have been to oversize the mould cavity volume (Vcavity).

For example, such an oversized mould cavity may be configured to mould other than the exact final shape, and allow for some sideways resin flow within the mould cavity to yield a variable sized part having oversize edges which are subsequently trimmed to size. The flow behaviour during cure is important to achieve the desired surface finish and properties. The resin must reach a high viscosity before the lull load is applied to avoid excess resin bleed.

Commonly this gives moulded parts, such as large surface area panels, with resin flow marks on the surface, and other imperfections.

When press moulding materials which include partially impregnated prepregs and/or dry fibres combined with one or more resin layers, it can be difficult to carry out the pressing to achieve full consolidation and resin impregnation of the dry fibres. When pressing pro-impregnated and SMC materials, the resin viscosity can be higher as compared to the resin used in partially impregnated prepregs or dry fibre-containing moulding materials, because there is no fibre to impregnate, and so it is easier to control the resin flow to avoid excess flow of the higher viscosity resins. In order to achieve lower costs and higher drape, which makes it easier to form the desired shape in the pressing operation, partially impregnated and/or resin film and dry fibre layers are preferred. However, although a lower viscosity is employed at lower pressure to impregnate the fibres, it is dilficult to avoid resin bleed out through the mould seals.

A further lmown improvement to the use of an oversized mould is to reduce the permeability at the fibre edges to allow a build-up of resin pressure and limit the resin bleed out. Typically the permeability is reduced by adding extra material to the edges and/or restricting the thickness to compress the stack, A mould cavity zone next to the reduced permeability area is also usually added to catch the resin flash. This method still does not give a net shaped part and trimming and post-finishing are necessary.

An oversize preform volume can be added and an area to collect resin flash can be added to the tool such that the moulded part can be a nearer net shape and less post-finishing is necessary. This is typically done by providing areas where the resin can cnter through a high tolerance tool gap into waiting mould area to collect the resin, or the resin overcoming an initial resin seal to from a layer of resin material. These flash catching zones can be problematic because during demoulding the thinner weaker resin flash can crack and selectively remain on the tool, which is difficult to clean for the next moulding cycle. Resin flash escaping over seals from the high resin pressure build up can quickly wear and damage the peripheral mould seals, leading to excessive resin bleed out on further cycles.

It is accordingly an aim of this invention to provide a press moulding apparatus and method which at least partially overcome at least some of these significant disadvantages of the known press moulding apparatus and methods currently used to manufacture moulded parts of fibre reinforced resin matrix composite material, in particular which manufacture such parts using prepregs.

The present invention provides an apparatus for press moulding materials to form a moulded part of fibre-reinforced resin matrix composite material, the apparatus comprising a mould tool defining a mould cavity, a recess in the mould tool which is in fluid communication with the mould cavity, and a resin trap device located in the recess, the resin trap device including a reservoir for containing excess resin and a pressure relief valve mechanism adapted to permit resin flow into the reservoir from the mould cavity when resin pressure on an outer inlet side of the valve mechanism is above a particular minimum threshold.

The present invention further provides a method of press moulding a moulding material to form a moulded part of fibre-reinforced resin matrix composite material, the method comprising the steps of i. locating a moulding material in a mould tool, the moulding material containing fibres and resin; ii. closing the mould tool to define a mould cavity containing the moulding material; iii. applying pressure to the mould cavity to cause resin to flow and impregnate the fibres; and iv. controlling resin pressure in the mould cavity by passing resin through a pressure relief valve mechanism and into a reservoir to contain excess resin when resin pressure on an inlet side of the valve mechanism is above a particular minimum threshold.

The present invention yet further provides a resin trap device including a reservoir for containing excess resin and a pressure relief valve mechanism adapted to permit resin flow into the reservoir when resin pressure on an outer inlet side of the valve mechanism is above a particular minimum threshold, whercin the valve mechanism includes an outer peripheral flange.

Preferred features are defined in the dependent claims.

Accordingly, the present invention provides an apparatus and method which arc particularly suitable for manufacturing parts composed of fibre reinforced resin matrix composite materials, such as, for example, panels, more particularly automotive body panels requiring no or limited subsequent trimming, machining or reworlc operations.

The apparatus and method incorporate a mechanism to capture and retain excess resin flash during the moulding at elevated pressure. This capture of excess resin flash enables prepregs and similar moulding materials, such as preforms, sheet moulding compounds (SMC) and multi-laminar moulding materials, accurately and consistently to be press mouldcd to a prcdcfined net shape. This is particularly important when manufacturing highly finished mouldings such as press moulded automotive body panels.

The preferred embodiments of the invention employ a resin trap device as a resin flash controller, which may comprise a disposable cup moulding with an integrated one-way pressure relief valve in a lid.

At the elevated moulding pressure, when the resin pressure exceeds a preset minimum value in the vicinity of the cup moulding, which minimum value is set by the opening pressure of the pressure relief valve, resin is urged through the pressure relief valve into the cup moulding which catches the excess resin. Capture of the excess resin correspondingly controls the moulding pressure, by reducing the resin pressure in the vicinity of the resin trap device.

The resin trap device is preferably composed of silicone thermoplastic clastomer and is a consumable item, together with the captured flash resin retained therein, in the moulding process. The resin trap device fits into a recess formed in the press moulding tool which is typically in a part of the mould which either forms a non-cosmetic area of the moulded part or is located at the perimeter of the mould cavity.

As the moulding material, for example prepreg, preform or SMC, is compressed in the tool and the resin begins to flow, the hydraulic pressure applied to the moulding material increases, which correspondingly increases the resin pressure, which in turn applies a fluid pressure to the relief valve which opens to absorb excess resin volume and then shuts when the fluid pressure acting on the relief valve is reduced as a result of resin flow into the resin trap device. The resin flash is contained in a disposable device, which reduces the frequency of mould cleaning which is required between successive moulding cycles.

It has been found that regulating the resin pressure within the mould cavity by using the resin trap device can provide more consistent moulding, in particular because the resin trap device(s) compensate for manufacturing tolerances of the moulding materials.

The press moulding apparatus and method of the invention may be employed for the press moulding of prepreg, multi-laminar, preform and SMC moulding materials, and may be used in a variety of applications, including but not limited to the press moulding of automotive body parts.

The press moulding apparatus and method of the invention may be employed to produce high volume, lightweight, low cost automotive body panels composed of composite material, and such production may incur minimal labour costs as a result of reducing or avoiding post-moulding finishing costs since the resin flash is miniinised or eliminated and the part is accurately moulded, The resin composition may be selected to havc a high degree of cross-linking, so as to have a high glass transition temperature Tg, with the result that the moulded part is able to be conveyed along a high temperature paint line without distortion or surface damage to maintain what is categorised for automotive body panels by those skilled in the art as a "class A" surface finish.

Embodiments of the present invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 illustrates a cross section through a mould tool including a resin trap device located a recess in the mould tool in accordance with a first embodiment of the present invention, the valve mechanism of the resin trap device being open; Figure 2 illustrates the mould tool of Figure 1 with the valve mechanism of the resin trap device being closed; Figure 3 illustrates a cross section through a mould tool including a resin trap device located a recess in the mould tool in accordance with a second embodiment of the present invention, and showing the reservoir partly filled with entrapped resin after a press-moulding operation; Figures 4 and S illustrate the mould tool of Figure 3 during after demoulding of the moulded part; Figure 6 illustrates a cross section through a mould tool including a resin trap device located a recess in the mould tool in accordance with a third embodiment of the present invention; and Figure 7 is a perspective view which illustrates the location of a plurality of resin trap devices relative to a door panel to he moulded by a mould tool in accordance with a fourth embodiment of the present invention.

Referring to Figures 1 and 2, there is shown a cross section through part o a mould tool 2 in accordance with a first embodiment of the present invention. l'he mould tool 2 comprises part of an apparatus for press moulding materials to form a moulded part of fibre-reinforced resin matrix composite material. The apparatus further comprises a press, typically hydraulically actuated, which urges together upper and lower mould parts 4, 6 which, when the mould is closed, defines a mould cavity 8 of predetermined volume, shape and dimensions, A recess 10, typically machii1ed, is provided in the mould tool 2 which is in fluid communication with the mould cavity 8. A resin trap device 12 is located in the recess 10.

The resin trap device 12 includes a reservoir 14 for containing excess resin. A pressure relief valve mechanism 16 is fitted to the reservoir 14. The pressure relief valve mechanism 16 is adapted to permit resin flow into the reservoir 14 from the mould cavity 8 when the resin pressure on an outer inlet side 18 of the valve mechanism 16 is above a particular minimum threshold, Typically, the valve mechanism 16 is adapted to permit resin flow into the reservoir 14 from the mould cavity 8 when the resin pressure on the outer inlet side 18 of the valve mechanism 16 is from 1 to 12 bar, optionally from 3 to 8 bar, still further optionally from 4 to 6 bar.

Preferably, the reservoir 14 is composed of an elastomeric material, optionally silicone elastomer and the valve mechanism 16 is also composed of an elastomeric material, optionally silicone elastomer. The reservoir 14 and the valve mechanism 16 are typically unitary, and they may be bonded together, optionally by welding together of elastomeric material in the reservoir 14 and the valve mechanism 16.

In the preferred embodiment, the valve mechanism 16 forms a substantially planar lid 17 for the reservoir 14, which may be substantially cup-shaped with the valve mechanism 16 being located at an open end 19 of the cup 20.

The resin trap device 12 is releasably located in the recess 10. The valve mechanism 16 includes an outer peripheral flange 22 which mates with a complementary recessed step 24 in a surface 26 of the mould tool 2, The outer peripheral flange 22 is fitted in the surface 26 by a compression fitting, which retains the resin trap device 12 in place when subjected to the moulding hydraulic pressure.

The valve mechanism 16 includes a deformable diaphragm member 28. In one embodiment the deformable diaphragm member includes a plurality of flaps separated by slits in the diaphragm, for example four flaps separated by a slit shaped in the form of a cross. In another embodiment, the deformable diaphragm membei' 28 includes a Belleville diaphragm.

Optionally, backup rings and stiffeners can also be moulded into the valve mechanism 16 to adjust the opening pressure.

In Figure 1 the valve mechanism 16 is shown open and in Figure 2 the valve mechanism 16 is shown closed. In the preferred embodiments, the valve mechanism 16 is a one-way valve mechanism permitting flow only into the reservoir 14 when the valve mechanism 16 is open as a result of a minimum positive pressure difference across the valve mechanism 1 6 from the outer inlet side 18 to the inner side 30.

Figures 3, 4 and 5 illustrate a second embodiment of the present invention.

In the second embodiment of Figures 3, 4 and 5, the resin trap device 12 is modified as compared to the device of Figures 1 and 2 by providing a compression seal member 34 on an outer peripheral edge 36 of the flange 22 which seals against an opposite edge 37 of the recessed step 24, The compression seal member 36 is fitted to or integral with the outer peripheral edge of the flange 22. The compression seal member 36 acts as a sealing ring moulded into the lid 17 which includes the valve mechanism 16. The compression seal member 36 seals against the recessed step 24. The compression seal member 36 is easy to push, locate mid retain in the recessed step 24.

The outer shape and dimensions of the reservoir 14 may be adapted to mate complementarily with the inner shape and dimensions of the recess 10. However, as shown in Figure 3, typically at least a bottom closed end 32 of the reservoir 14 may be spaced by a gap 33 from the inner surface 34 of the recess 10 to provide room for expansion of the reservoir 14 when subjected to resin pressure during the moulding operation, and which may facilitate removal of the resin trap device 1 2 from the recess tO after the press-moulding process.

The provision of an integral or two-piece moulding resin trap device 12 comprising the reservoir 14 and the flange 22 of the valve mechanism 16 provides that the recess 10 and recessed step 24 are easy to manufacture. The flange 22, optionally with the compression seal member 36, can securely but temporarily fit the resin trap device to the recessed step 24, and the tolerance of the recess 10 relative to the reservoir t4 is not critical. A gap 33 can exist between the resin trap device 12 and the recess 10, Initially during the press-moulding process, the resin trap device 12 is fitted into the recess 10 so as securely but temporarily to be retained thercin.

Typically, the recess 10 is located at a major moulding surface 38 of thc mould tool 2.

However, as described further below, preferably the resin trap device 12 is located on a mould tool surfacc 38 which defines a low tolerance moulding surface of the mould tool 2, i.c. not a highly finished surfacc of the moulded part, for example a rear surface of an automotive body panel which is, in use, hidden from view.

As shown in Figures 4 and 5, the major moulding surface 38 defines, together with an opposite mould tool surface 40 when the mould tool 2 is closed, the mould cavity 8 which moulds a portion of the resultant moulded part 42 having a maximum thickness of 75 mm, optionally athiekness of from ito 15mm.

During the moulding operation, the moulding material is laid up into the mould tool 2 and the mould tool 2 is closed to define the mould cavity 8. The temperature and pressure are increased to consolidate the moulding material and cause the resin to flow throughout the entire mould cavity 8 and fully impregnate the fibrous material of the moulding material, The moulding material charge has been selected so as to have a greater volume than the volume of the mould cavity 8, Therefore during the moulding process the hydraulic pressure of the resin increases during the consolidation and impregnation steps to ensure resin flow throughout the entire mould cavity 8, and ensure full and consistent resin impregnation.

If the hydraulic pressure of the resin increases above a minimum threshold determined as the opening pressure of the one-way valve mechanism 16, excess resin flows into the reservoir 14 through the open valve mechanism 16 resulting from the establishment of a hydraulic pressure equal to or exceeding the minimum positive pressure difference across the valve mechanism 16 from the outer inlet side 18 to the inner side 30 which is required to open the valve. The excess resin 44 is trapped within the reservoir 14, as shown in Figure 4.

Since the liquid resin is under high pressure, initially the resin may impact the inner rear end of the reservoir 14 and drip back to form a body of excess resin 44 in the resin trap device 12. The valve mechanism 16 then shuts as the resin pressure drops below the opening threshold pressure. The relief pressure threshold is set sufficiently high enough to ensure sufficieni hydraulic pressure to have the desired resin flow within the entire composite moulded part 42 before the pressure is relieved by the valve mechanism 16 and the excess volume of resin retained in the resin trap device 12. Accordingly, the desired resin pressure is maintained throughout the remainder of the moulding process, The reservoir 14 encloses the still liquid excess resin 44. Further tool closure or compression may cause the resin pressure to rise again, with the valve mechanism 16 reopening and closing again control the pressure. This excess resin 44 solidifics and cures together with the curing of the composite moulded part during the mould cycle.

The present invention has particular application in the press moulding of multilayer moulding material structures incorporating partially impregnated or unimpregnated prepregs and/or resin layers. This moulding material has an initial volume Vprefonm During typical vacuum consolidation and cure this volume reduces, after elimination of air and full impregnation of any dry fibres, to a final volume Vcure. By considering the desired volume Ypart of the final moulded and the manufacturing tolerances of the laminate stack, the laminate stack can be made such that Ycure is always greater than Ypart. As described above, this generates a high hydraulic pressure in the part, ensuring frill resin impregnation, and by using the resin trap devices 12 this excess volume can be accommodated by a volume of resin entering the resin trap devices 12 through the integral pressure relief valve mechanisms 16, which controls and ensures a consistent moulding pressure.

After the prcss moulding operation has terminated and the resin has filly cured, the mould tool 2 is opened as shown in Figures 4 and 5, and the moulded part 42 is demoulded from the mould tool 2. The reservoir 14 of the resin trap device 12 is easily pulled out of the recess 10 as the moulded part 42 is removed from the mould tool 2. The resin trap device 12 is easy to remove since it is flexible, for example being made of silicone elastomer, and is connected to the moulded part 42 only by a thin web or line 46 of resin passing through the valve gap and by surface contact of the outer surface 47 of the lid 17 of the valve mechanism 16 with the adjacent face 49 of the moulded part 42. By placing the resin trap device 12 in the upper tool part 4, it is more likely for a thin volume of resin passing through the valve gap to connect the excess resin 44 in the flash controller to the resin of tl1e composite inoulded part 42 which assists automatic removal of the resin trap device 12 from the mould recess 10.

The resin trap device 12 may therefore be temporarily attached to the moulded part 42 by a narrow web or line of resin 46 which extends between the moulded part 42 and the excess resin 44 trapped within the reservoir 14. The narrow web or line of resin 46 can readily be snapped without any damage to the moulded part 42 and with minimal subsequent work to finish the surface 49 of the moulded part 42.

Figure 6 illustrates a modification in which the tool gap 50 is narrowed at the location of the resin trap device 12. The width of the mould cavity 8 is reduced at this mould cavity region 52 and the preform portion 56 initially disposed into the mould cavity region 52 consists of a resin film, for example a surface layer 58 for forming a surface of an automotive body panel 54. The remaining fibrous plies of the main laminate portions 60 arc absent from this narrow width mould cavity region 52. The surface resin layer communicates the hydraulic pressure to the resin trap device 1 2.

Although only a single resin trap device is illustrated in Figures 1 to 6, the apparatus of the present invention may comprise a plurality of resin trap devices, each being located in a respective recess, the resin trap devices being mutually spaced in the mould tool and about the mould cavity. Typically, but not essentially, the resin trap devices 12 are in the upper mould part 4, but they may be in the lower mould part 6 or in both the upper and lower mould parts 4, 6.

The number of resin trap devices may additionally be determined by the volume of the reservoir and the expected volume of resin to be trapped, to ensure that the reservoir volume is sufficient to trap al the likely excess resin. Typically, the resin trap device has a volume from 10 to 200 mL, optionally from 25 to 100 mL. For an automotive body panel, the total resin trapped by the resin trap devices may comprise from 100 to 1000 mL.

The resultant cured resin formed from the preform portion 56 may be associated with a portion of the moulding which is to be cut away and discarded, leaving an opening or cut profile in the resultant part. By locating the resin trap device 12 adjacent to the narrow gap, any surface effect on the moulded surface resulting from the resin connection of the web or line 46 of resin to the excess resin 44 trapped within the reservoir 14 would not be present in the final moulded part since the resultant cured resin comieeted to the web or line 46 is cut away from the final moulded part.

For example, when moulding an automotive body panel, the tool gap 50 is narrowed and the resin trap device 12 located in an area such as the automotive door handle cut out 60, shown in Figure 7 which illustrates an automotive body panel 64 moulded in accordance with an embodiment of the present invention. Figure 7 shows location of resin trap devices around the perimeter of the automotive door moulding and in a handle cut-out location. This mould structure has the advantage of forming the edge detail of the panel surrounding the door handle and sealing in the fibre reinforcement within the resin at the cut edge when the part is trimmed by cutting out the opening for the door handle prior to fitting the handle.

A further advantage of this mould structure is that, on demoulding, a continuous layer of resin extends over the entire moulded part. The resin in the preform portion 56 has a controlled thickness which is sufficient to avoid inadvertent breakage of the resin during demoulding. Unlike a very thin resin flash line as encountered in the prior art, as discussed above, the controlled thickness of resin in the later cut-out detail layer is unlikely to shatter or leave only a part remaining on the tool surface. The cured moulded part is more likely to de-mould cleanly, without leaving any resin in the mould, saving time for cleaning the mould between moulding cycles.

The panel of Figure 7 may be moulded using plural resin trap devices 12, each located at a respective spaced location 66. These plural locations 66 may be located adjacent to thin channel of the mould cavity, similar to narrow width mould cavity region 52 of Figure 6, and corresponding strips of surface film 62, similar to surface layer 58 of Figure 6, can be used to communicate the hydraulic resin pressure to the resin trap devices 12. The remaining tool cavity can close to a more precise fit to from a net shape edge with very little resin flash, thereby reducing post moulding operations.

Such a surface film 62 is typically a layer of resin with an optional fillers and optional fibre reinforcement. For example, the surface resin film may be provided on a back surface thereof with a very thin glass fibre reinforcement layer, for example a 70 gsm woven glass fibre fabric or scrim. This fibre reinforcement layer increases the strength of the surface film 62 and enables the surface film 62 to de-mould without damage, the fibre reinforcement layer preventing breakage or cracking of the surface film 62 on dc-moulding.

By using one or more resin trap devices 12, the excess volume of the preform moulding material can be accommodated by permitting the excess volume of resin to enter and he trapped in the reservoir(s) 14 by controlled passage of resin through the integral pressure relief valve mechanism 16. The integral pressure relief valve mechanism 16 then controls the resin moulding pressure, and ensures that the resin moulding pressure is consistent. Since the excess resin is eliminated, the resultant moulded part may have an improved weight tolerance as compared to moulding without controlled trapping of resin flash.

Various modifications to the illustrated embodiments of the invention will be readily apparent to those skilled in the art.

Claims

CLAIMS1. An apparatus for press moulding materials to form a moulded part of fibre-reinforced resin matrix composite material, the apparatus comprising a mould tool defining a mould cavity, a recess in the mould tool which is in fluid communication with the mould cavity, and a resin trap device located in the recess, the resin trap device including a reservoir for containing excess resin and a pressure relief valve mechanism adapted to permit resin flow into the reservoir from the mould cavity when resin pressure on an outer inlet side of the valve mechanism is above a particular minimum threshold.
2. An apparatus according to claim I wherein the resin trap device is releasably located in the recess.
3. An apparatus according to claim 1 or claim 2 wherein the reservoir is composed of an elastomeric material, optionally silicone elastomer.
4. An apparatus according to any one of claims I to 3 wherein the valve mechanism is composed of an elastomeric material, optionally silicone elastomer.
5. An apparatus according to any foregoing claim wherein the reservoir and the valve mechanism are unitary.
6. An apparatus according to claim 5 wherein the reservoir and the valve mechanism are bonded together, optionally by welding together of elastomeric material in the reservoir and the valve mechanism,
7. An apparatus according to any foregoing claim wherein the valve mechanism is a one-way valve mechanism permitting flow only into the reservoir.
8. An apparatus according to any foregoing claim wherein the valve mechanism fonTis a substantially planar lid for the reservoir.
9, An apparatus according to any foregoing claim wherein the valve mechanism includes an outer peripheral flange which mates with a complementary recessed step in a surface of thc mould tooling.
10. An apparatus according to claim 10 wherein the outer peripheral flange is fitted in thc surface of the mould tooling by a compression fitting.
11. An apparatus according to claim 10 further comprising a compression seal member which seals against an opposite edge of the recessed step.
12. An apparatus according to claim 11 whercin the compression seal member is located on the outer peripheral edge of the flange.
13. An apparatus according to any foregoing claim wherein at least a portion of an outer surface of the reservoir is spaced from an inner surface of the recess,
14. An apparatus according to any foregoing claim wherein the valve mechanism is adapted to permit resin flow into the reservoir from the mould cavity when the resin pressure on the outer inlet side of the valve mechanism is from 1 to 12 bar, optionally from 3 to 8 bar, further optionally from 4 to 6 bar.
15. An apparatus according to any foregoing claim wherein the valve mechanism includes a defonnable diaphragm member.
16. An apparatus according to claim 15 wherein the defonnable diaphragm member includes a plurality of flaps separated by slits in the diaphragm.
17. An apparatus according to claim 15 wherein the deformable diaphragm member includes a Belleville diaphragm.
18, An apparatus according to any foregoing claim comprising a plurality of a resin trap devices, each being located in a respective recess, the resin trap devices being mutually spaced in the mould tool and about the mould cavity.
19. An apparatus according to any foregoing claim wherein the resin trap device is located on a mould tool surface which defines a low tolerance moulding surface of the mould tool.
20. An apparatus according to any foregoing claim wherein the resin trap device is located on a mould tool surface which, together with an opposite mould tool surface when the mould tool is closed to define the mould cavity, defines a portion of the moulded part having a maximum thickness of 75 mm, optionally a thickness of from 1 to 15mm.
2 I. An apparatus according to any foregoing claim wherein the reservoir is substantially cup-shaped and the valve mechanism is located at an open end of the cup.
22. A method of press moulding a moulding material to form a moulded part of fibre-rehiforced resin matrix composite material, the method comprising the steps of: i. locating a moulding material in a mould tool, the moulding material containing fibres and resin; ii. closing the mould tool to define a mould cavity containing the moulding material; iii. applying pressure to the mould cavity to cause resin to flow and impregnate the fibres; and iv. controlling resin pressure in the mould cavity by passing resin through a pressure relief valve mechanism and into a reservoir to contain excess resin when resin pressure on an inlet side of the valve mechanism is above a particular minimum threshold.
23. A method according to claim 22 wherein the pressure relief valve mechanism and reservoir are comprised in a resin trap device releasably located in a recess in the mould tool.
24. A method according to claim 22 or claim 23 wherein the reservoir is composed of an elastomeric material, optionally silicone elastomer.
25. A method according to any one of claims 22 to 24 wherein the valve mechanism is composed of an elastomeric material, optionally silicone elastomer, 26, A method according to any one of claims 22 to 25 wherein the valve mechanism is a one-way valve mechanism permitting flow only into the reservoir.27. A method according to any onc of claims 22 to 26 wherein the valve mechanism includes an outer peripheral flange which mates with a complementary recessed step in a surface of the mould tooling.28. A method according to any one of claims 22 to 27 wherein the valve mechanism is adapted to permit resin flow into the reservoir from the mould cavity when the resin pressure on the outer inlet side of the valve mechanism is from 1 to 12 bar, optionally from 3 to 8 bar, further optionally from 4 to 6 bar.29. A method according to any one of claims 22 to 26 wherein the valve mechanism includes a deformable diaphragm member.30, A method according to claim 29 wherein the deformable diaphragm member includes a plurality of flaps separated by slits in the diaphragm.31. A method according to claim 29 wherein the defonnable diaphragm member includes a Belleville diaphragm.32. A method according to any one of claims 22 to 31 comprising a plurality of valve mechanism and associated reservoir assemblies, the plural assemblies being mutually spaced in the mould tool and about the mould cavity.33, A method according to any one of claims 22 to 32 wherein the valve mechanism is located on a mould tool surface which defines a low tolerance moulding surface of the mould tool.34. A method according to any one of claims 22 to 33 wherein the valve mechanism is located on a mould tool surface which, together with an opposite mould tool surface when the mould tool is closed to define the mould cavity, defines a portion of the moulded part having a maximum thickness of 75 mm, optionally a thickness of from Ito 15mm.35. A method according to any one of claims 22 to 33 wherein the valve mechanism is located on a mould tool surface which, together with an opposite mould tool surface when the mould tool is closed to define the mould cavity, forms a portion of the moulded part which is composed solely of resin.36. A resin trap device including a reservoir for containing excess resin and a pressure relief valve mechanism adapted to peimit resin flow into the reservoir when resin pressure on an outer inlet side of the valve mechanism is above a particular minimum threshold, wherein the valve mechanism includes an outer peripheral flange.37. A resin trap device according to claim 36 wherein the reservoir is composed of an elastomeric material, optionally silicone elastomer.38. A resin trap device according to claim 36 or claim 37 wherein the valve mechanism is composed of an elastomeric material, optionally silicone elastomer.39. A resin trap device according to any one of claims 36 to 38 wherein the reservoir and the valve mechanism arc unitary.40. A resin trap device according to claim 39 wherein the reservoir and the valve mechanism are bonded together, optionally by welding together of elastomeric material in the reservoir and the valve mechanism.41, A resin trap device according to any one of claims 36 to 40 wherein the valve mechanism is a one-way valve mechanism permitting flow only into the reservoir.42. A resin trap device according to any one of claims 36 to 41 further comprising a compression seal member on an outer peripheral edge of the flange.43. A resin trap device according to claim 42 wherein the compression seal member is located on the outer peripheral edge of the flange.44. A resin trap device according to any one of claims 36 to 43 wherein the valve mechanism is adapted to permit resin flow into the reservoir when the resin pressure on the outer inlet side of the valve mechanism is from ito 12 bar, optionally from 3 to 8 bar, further optionally from 4 to 6 bar.45. A resin trap device according to any one of c'aims 36 to 44 wherein the valve mechanism includes a deformable diaphragm member.46. A resin trap device according to claim 45 wherein the deformable diaphragm member includes a plurality of flaps separated by slits in the diaphragm.47. A resin trap device according to claim 45 wherein the deformahie diaphragm member includes a Befleville diaphragm.48. A resin trap device according to any one of claims 36 to 47 wherein the reservoir is substantially cup-shaped and the va've mechanism is formed in a lid located at an open end of the cup.49. A moulded part of fibre-reinforced resin matrix composite material press moulded by the method of any one of claims 22 to 35.