The present and future of carbon fibre

Technology

The present and future of carbon fibre

Car makers around the world are continually working on making cars lighter and stronger. We only see the end result of what can be years of development and testing to bring new materials into cars that will not awaken litigation from consumers.
While aluminium has been around for decades as a material for body panels, it has only recently been pressed into service for more structurally critical parts of the car. The Jaguar XJ series and now the latest sports offering from Jaguar are virtually all aluminium.
High Strength steels are becoming more popular in car manufacture because they offer additional strength for less weight. And like aluminium they require a whole different approach to repair, including the re-training of technicians and the purchasing of new equipment ? especially welders.
Carbon fibre is another build material that is being investigated increasingly by car makers because it is offers new levels of strength and lightness. And unlike other car body materials, it is non-metal.
CARBON FIBRE
The full term is 'carbon fibre reinforced composite'(CRFC). A composite is a combination of two or more materials that, when combined, make up a stronger material. Fibreglass is an example of another composite. Fibreglass parts are generally made using a polyester resin whereas CRFC is a mixture of fibres made from carbon and an epoxy resin. When the resin is hardened the carbon fibres reinforce the material, making it extremely strong. The strength comes from having the correct percentage of resin to carbon fibres, as well as the orientation of the carbon strands. The excessive strength due to the strength of the carbon and the orientation of the strands allows vehicle engineers to build a lighter and thinner body part, yet maintain the strength and rigidity found in traditional metals.
USES
Currently, vehicles which use CFRC are mostly high priced sports cars. Like all raw material developments, CFRC has begun as exotic and rare but increased usage and handling skill will bring it towards the mass market.
General Motors introduced CFRC as the hood on the 2004 special edition Corvette Z06. It resulted in a weight saving of 56 per cent over a steel hood while exceeding steel's strength. The Corvette also uses carbon fibre for the front guards and part of the wheel housing with spectacular reductions in weight and thickness. The rigidity of carbon fibre for the guard application also reduces the need for reinforcements required for thermal expansion, creating further weight saving. Ferrari, McLaren, Mercedes Benz, BMW M3, Acura NSX-R, and Aston Martin all use carbon fibre in their exotic, but essentially street cars. Many racing cars use carbon fibre as a matter of course. Often a sports race car such as a Porsche 911 will look as though it has a standard factory body, but closer examination will reveal that the body has actually been reproduced in carbon fibre.
REPAIRING CARBON FIBRE
Carbon fibre is not easy to repair, certainly when compared to mild steel. Above all, it is essential to follow the car maker's instructions. When CFRC is moulded into shape the mixture of the resin and carbon is said to be a primary bond ? in which state it is at maximum strength. All subsequent repairs are called secondary bonds, meaning the integrity of the repair depends on the adhesive properties of the repair resins and adhesives. While structural parts are usually replaced, cosmetic body panels can sometimes be repaired. For instance, GM allows new Corvette guards to be repaired as long as the damage doesn't reach the edge of the panel.
Damage such as a puncture or tear that protrudes through the panel calls for a two sided repair in which it is necessary to make a large taper to maximise the amount of surface area the repair materials can adhere to. The exact procedure is generally available from car makers using carbon fibre.
As carbon fibre becomes increasingly used, so adhesive manufacturers will carry on their own research to make its repair easier. We're currently at the 'lead wiping and file finish' stage of repairing carbon fibre. Ahead of us is the equivalent of plastic filler.