Thematic Curing of Sectional Fiber Composite Repair

Vehicle body construction is becoming lighter and stronger for reasons of environment, economics and safety. Repairability of new materials always becomes a challenge to replicate in a re-manufacture process.

A new challenge on the horizon is the increase of carbon fiber composite technology into mainstream vehicle manufacturing.

At the recent International Tokyo Motor Show, held in early December, a clear change in technology was evident with most major brands showcasing hybrids and electric vehicles. To keep the vehicle weight down, the use of ultra-lightweight composites is necessary.

We talked to David Benbow, a recognized authority on the repair of carbon fiber, for his opinion about what it means for the body and paint industry.

David, composite bodies in the manufacturing of vehicles are now becoming mainstream. Why is that?

The bottom line answer is the fuel/energy efficiency being sought by all manufacturers of all types of vehicles; whether they be cars, buses, trucks, trains or planes. Part of that equation is weight saving, and composites contribute hugely to that part of the equation.

What does that mean for the body repair industry?

Largely, it will require a change of mind-set. Composite materials are a relatively new concept. Early experimentation started around the 1940’s in the military, so there is approximately 70 years of experience working with these materials. Metal, on the other hand, has been worked with for thousands of years so there is much more of a database to work from. To get the best out of composite design requires a different approach to getting the best out of metal. Likewise, the repair of such materials requires a different approach. That said, composites being relatively new, there is constant development of materials and

methodologies in the search for more cost-effective production and repair solutions. Two factors, which currently can be viewed as negatives in the composite arena, are 1) the cost of materials and 2) the fact that the work is very labor intensive. Both of these areas are under constant development to reduce costs.

So, in summary, the body repair industry will need to understand the basics of the material and its manufacture; when armed with this knowledge it will have a better understanding of how to perform the repair. The fastest way to gain knowledge will be through recognized training.

Does the repair process differ for body repair and paint?

To repair composites, all paint in the area of the repair will need to be removed before any repair is undertaken. There are specific ways of removing paint which must be adhered to, as the use of incorrect chemicals could cause irreparable damage to the part. The actual repair of a composite is very different to the repair of a metal part. All of the correct techniques can be learned through appropriate training. Final paint of a repaired area will, again, require some specific primer materials in order to generate a Class A surface finish. These may well be manufacturer dependent.

What warrants replacement on a damaged composite panel?

All composite damage is repairable. The question is: what is economically repairable? Can it be repaired to an acceptable standard at a price less than replacement? This may well become industry- or insurance-led with manufacturers, through appropriate training which sets out specific targets.

There may be circumstances whereby replacement parts are not available, in which case reconstruction techniques would need to be employed. Such techniques could include partial mold production from original panels to give the base for reconstructing the exact shape of a repaired panel. There are many techniques available which can be learned from more advanced training.

Composite materials do require a setting time and the chemistry of a particular resin system will determine that time. Another influential factor on setting times is temperature and humidity. For example, a repair in a cold workshop in the UK will require a different approach to that in a warm humid workshop in Malaysia. There are many different products available from manufacturers that take into account these climatic variations.