GB2491359A

GB2491359A - Imitation carbon fibre composite comprising glass fabric, resin and pigment

Info

Publication number: GB2491359A
Application number: GB1109081.8A
Authority: GB
Inventors: Martin Chambers
Original assignee: McLaren Automotive Ltd
Current assignee: McLaren Automotive Ltd
Priority date: 2011-05-31
Filing date: 2011-05-31
Publication date: 2012-12-05
Anticipated expiration: 2031-05-31
Also published as: GB2491359B; GB201109081D0

Abstract

The composite material comprises a woven glass fibre mat 101 in a cured resin 103. The woven glass fibre mat 101 has a reflective coating 102, preferably of aluminium oxide. A surface of the composite material overlying the coated surface 102 of the mat 101 is further coated by a translucent paint mixture 104. The translucent paint mixture 104 comprises clear coat paint and 4-12 wt% black pigment. The method of producing the composite by moulding (preferably in an autoclave) and coating (preferably after rubbing down with fine adhesive) is also claimed. Preferably, a scratch resistant clear coat paint 105 is applied to the composite, which is then polished to a mirror finish.

Description

I

Imitation Carbon Fibre

BACKGROUND OF THE INVENTION

This invention relates to a composite material and its manufacture.

The high tensile strength and low density of carbon fibre composites has led to their extensive use in aerospace and motorsport, as well as in all manner of vehicular, sporting and medical applications that demand excellent mechanical performance. However, carbon fibre composites are expensive compared with many other materials and its use is therefore generally limited to situations in which mechanical performance is of paramount importance and cost is a less important factor. This has led to the development of a strong association between carbon fibre composites and luxury items such as high performance cars and bicycles.

As a result of the association of carbon fibre to expensive, high performance articles, it has become desirable for lower-value articles to be fashioned so as to appear as though they are made at least partly from carbon fibre composites. For example, some low-end bicycle parts are made from conventional low-cost alloys wrapped in a thin veneer of carbon fibre or imitation carbon fibre so as to appear as though the bicycle part is made from carbon fibre composite. Similarly, it is becoming common for after-market car parts such as body trim, spoilers and interior fillings to be manufactured from conventional metals or plastics at least partly wrapped in a thin veneer of carbon fibre or imitation carbon fibre. Typically the carbon fibre veneer is a thin layer of low quality carbon fibre, or is a material (e.g. PVC, plastic or leather) embossed and painted so as to imitate the appearance of carbon fibre composite.

Imitation carbon fibre articles do not provide the mechanical benefits of true carbon fibre composite articles and generally have the properties of the metal or plastic substrate on which the carbon fibre (fake or real) veneer is supported.

Furthermore, even in cases in which the use of imitation carbon fibre is solely aesthetic, the veneer layer is generally very thin and if scratched or damaged can reveal the underlying structure of the imitation carbon fibre part.

There is therefore a need for an imitation carbon fibre composite that has an improved likeness to real carbon fibre and that offers improved mechanical characteristics over conventional imitation carbon fibre articles.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a composite material comprising a woven glass fibre mat in a cured resin, at least a first surface of the woven glass fibre mat having a reflective coating and a surface of the composite material overlying the first surface of the woven glass fibre mat being coated in a translucent paint mix comprising a clear coat paint and a black pigment, the black pigment being between 4% and 12% of the translucent paint mix by weight.

The translucent paint mix preferably comprises black pigment and clear coat paint in a ratio of 8:100 by weight.

Preferably the reflective coating is aluminium oxide.

Preferably the thickness of the coating is less than 100 nm.

Preferably the black pigment has Pantone reference Jet Black RAL 9005, Signal Black RAL 9004, or Graphite Black RAL 9001.

According to a second aspect of the present invention there is provided a method of finishing a glass fibre composite material comprising: arranging a woven glass fibre mat in a mould, at least a first surface of the woven glass fibre mat having a reflective coating; moulding the woven glass fibre mat with a resin so as to cure the woven glass fibre mat and resin and produce a glass fibre composite material; and coating a surface of the glass fibre composite material overlying the first surface of the woven glass fibre mat with a translucent paint mix comprising a clear coat paint and a black pigment, the black pigment being between 4% and 12% of the translucent paint mix by weight.

The method preferably further comprises: coating said surface of the composite material with a scratch-resistant clear coat paint; and polishing the scratch-resistant clear coat paint to a mirror finish.

The method preferably further comprises, prior to the coating step, rubbing down the surface of the moulded glass fibre composite material with a fine abrasive.

Suitably the step of moulding performed by compression moulding in an autoclave.

Preferably the reflective coating is aluminium oxide.

Preferably the thickness of the coating is less than 100 nm.

DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic cross-section of a composite material according to the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The following description is presented to enable any person skilled in the ad to make and use the invention, and is provided in the context of a particular application. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art.

The general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention.

Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

The present invention relates to a glass fibre composite material having good mechanical characteristics and being significantly cheaper than an equivalent carbon fibre composite material. A glass fibre composite article manufactured according to the present invention can replace an equivalent carbon fibre composite article whilst retaining the appearance of carbon fibre. The low cost of a glass fibre composite material of the present invention also allows it to be used where the appearance of carbon fibre is desired but carbon fibre cannot be used due to its high cost.

Figure 1 shows a cross-section of a glass fibre composite material according to the present invention. The material comprises a woven mat of glass fibres 101 supported in a resin 103. The woven mat is coated so as to be reflective: in figure I the mat is coated on one side with a layer of aluminium oxide 102. It is important that the reflective coating is sufficiently thin so as to ensure that the weave of the glass fibres is not masked by the reflective coating. The reflective coating is applied to the mat prior to sealing the mat in resin. Once the basic composite material formed by the glass fibre mat and resin has been formed, the surface of the material overlying reflective layer 102 is coated with a translucent paint mix 104 comprising a clear coat paint mixed in a specific ratio with a black pigment. Preferably, the surface of the composite material is further coated with a scratch-resistant clear coat paint or lacquer (such as BASF Glasurit 923-447) polished to a high gloss.

An exemplary method of manufacture of the glass fibre composite of figure 1 will now be described. Firstly, a glass fibre mat 101 supporting a reflective coating 102 is prepared. The glass fibres could be woven in any kind of weave, but preferably a weave commonly used in carbon fibre mats is selected, such as a 2x2 twill pattern. The reflective coating could be applied to the glass fibre mat by coating the fibres once the mat has been woven or by coating the glass fibres prior to weaving the glass fibres into the mat. The reflective coating is preferably aluminium oxide, but could be another reflective material (such as another metal or metal oxide) suitable for use with a resin 103. Preferably the reflective coating is very thin so as to not modify the mechanical properties of the glass fibre mat: typically a coating of aluminium oxide would be around 20 nm in thickness.

Typically only one side of the glass fibre mat will be visible in the finished article and it is therefore preferable that the reflective coating is applied to only one side of the mat. Glass fibre mats coated with a reflective material are commercially available. For example, one such mat is marketed under the brand name Texalium (RTM), which comprises glass fibres coated on one side with aluminium oxide. Note that in the step of applying the reflective coating to the glass fibres it is aluminium that is deposited rather than aluminium oxide, but the aluminium rapidly oxidises to form aluminium oxide.

The glass fibre mat is then formed into the desired composite article by impregnating the mat with a resin (typically by dipping, or injection) and curing the resin whilst the mat and resin is held in the desired configuration. This can be achieved by compression moulding in an autoclave, resin transfer moulding, pressure bag moulding, vacuum bag moulding, casting or any other suitable techniques. Preferably the mat is dipped in resin and then compression moulded since this offers a low cost and high throughput method of manufacture.

Preferably the resin is a clear resin.

Once the basic composite article has been formed and the surface of the article prepared (e.g. by rubbing down the surface with a fine abrasive), the surface of the composite is coated with a translucent paint mix comprising a specific ratio of clear coat paint to black pigment. Preferably the black pigment used has Pantone reference Jet Black RAL 9005, but black pigments having Pantone references Signal Black RAL 9004 or Graphite Black RAL 9011 could alternatively be used.

Importantly, the proportion of black pigment in the translucent paint mix as a percentage by weight is between 4% and 12%. BASF Glasurit A926 Black has been found to provide good results. Most preferably the ratio of black pigment to clear coat paint is 8:100 by weight, such that the mix comprises 8g of pigment to every lOOg of clear coat. This particular tint of translucent paint has been found to result in a composite article that is almost indistinguishable from a true carbon fibre composite.

It is advantageous if a further scratch-resistant clear coating 105 is applied to the surface of the translucent paint mix, such as a scratch-resistant clear coat paint, lacquer or varnish. This protects the tinted translucent paint beneath and helps ensure that any scratches to the surface of the composite article do not reveal or penetrate the tinted paint layer. The scratch-resistant clear coating is polished to a high gloss mirror finish so as to best mimic the lacquered finish typically given to carbon fibre composites. Alternatively, if no scratch-resistant coating is applied, the surface of the translucent paint mix is itself polished smooth to a high shine.

The present invention provides a composite material that has the good mechanical characteristics of a glass fibre composite but the appearance of substantially more expensive carbon fibre composite. Furthermore, since glass fibre composite is transparent to radio frequencies, a composite article prepared in accordance with the present invention can be used where radio freqeuency (RF) transparency is required. This provides an alternative to carbon fibre composites that cannot be used in such situations because carbon fibre significantly attenuates radio frequencies. For example, a composite article prepared in accordance with the present invention could be used as an antenna housing that provides mechanical characteristics close to that of a carbon fibre composite and the appearance of a carbon fibre composite.

In the example given in figure 1 only one side of the glass fibre mat is coated with a reflective material. In alternative embodiments of the present invention, both sides of the mat could be coated with the reflective material -this could be useful if both sides of the article are going to be visible in use. Importantly, the translucent paint mix is applied to the surface of the composite article overlying the reflective layer. Thus, if both sides of the mat were coated with the reflective material, both sides of the composite article could be coated with the translucent paint mix so as to provide the appearance of carbon fibre from both sides. It is the combination of reflective woven glass fibre mat and overlying translucent paint mix that provide the surprisingly convincing carbon fibre appearance of a glass fibre composite article according to the present invention.

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

Claims

CLAIMS1. A composite material comprising a woven glass fibre mat in a cured resin, at least a first surface of the woven glass fibre mat having a reflective coating and a surface of the composite material overlying the first surface of the woven glass fibre mat being coated in a translucent paint mix comprising a clear coat paint and a black pigment, the black pigment being between 4% and 12% of the translucent paint mix by weight.
2. A composite material as claimed in claim 1, wherein the translucent paint mix comprises black pigment and clear coat paint in a ratio of 8:100 by weight.
3. A composite material as claimed in claim I or 2, wherein the reflective coating is aluminium oxide.
4. A composite material as claimed in claim 3, wherein the thickness of the coating is less than 100 nm.
5. A composite material as claimed in any preceding claim, wherein the black pigment has Pantone reference Jet Black RAL 9005, Signal Black RAL 9004, or Graph ite Black RAL 9001.
6. A method of finishing a glass fibre composite material comprising: arranging a woven glass fibre mat in a mould, at least a first surface of the woven glass fibre mat having a reflective coating; moulding the woven glass fibre mat with a resin so as to cure the woven glass fibre mat and resin and produce a glass fibre composite material; and coating a surface of the glass fibre composite material overlying the first surface of the woven glass fibre mat with a translucent paint mix comprising a clear coat paint and a black pigment, the black pigment being between 4% and I 2% of the translucent paint mix by weight.
7. A method as claimed in claim 6, further comprising: coating said surface of the composite material with a scratch-resistant clear coat paint; and polishing the scratch-resistant clear coat paint to a mirror finish.
8. A method as claimed in claim 6 or 7, further comprising, prior to the coating step, rubbing down the surface of the moulded glass fibre composite material with a fine abrasive.
9. A method as claimed in any of claims 6 to 8, wherein the step of moulding performed by compression moulding in an autoclave.
10. A method as claimed in any of claims 6 to 9, wherein the reflective coating is aluminium oxide.
II. A method as claimed in claim 10, wherein the thickness of the coating is less than 100 nm.
12. A method as claimed in any of claims 6 to 11, wherein the black pigment has Pantone reference Jet Black RAL 9005, Signal Black RAL 9004, or Graphite Black RAL 9001.
13. A composite material substantially as described herein with reference to figure 1.