Repair vs. replace: What you need to know about carbon fiber

June 18, 2015
Knowing when and how to repair newer materials, such as carbon fiber, and whether the repairs are structural or cosmetic, will allow you to make the best recommendations to your customer and add to your profitability.

“Repair vs. Replace” is not a new issue in the collision repair industry. However, as new substrate materials are pioneered by car manufacturers, the decision of “repair vs. replace” becomes even more significant to your business. Knowing when and how to repair these newer materials, such as carbon fiber, and whether the repairs are structural or cosmetic, will allow you to make the best recommendations to your customer and can add to your profitability. 

What is Carbon Fiber?
Carbon fiber has been used in automobile production for about 20 years, and more frequently over the past five years, typically for high-end vehicles such as BMWs and Corvettes. Carbon fiber is composed of thin carbon filaments that are bound together with a plastic polymer resin to form a composite material. The fibers are woven into a complex weave that is both strong and lightweight. Carbon fiber does not contain any metal elements.

It is carbon fiber’s strong, lightweight properties, along with its “woven” look,  that make it so appealing to car designers, especially for visible cosmetic panels on high-end vehicles. Although carbon fiber is more costly than traditional composites and more costly than metals, such as steel or aluminum, new production techniques are reducing the cost factor. An equivalent panel of carbon fiber is also much thinner and lighter than a fiberglass weave.

While carbon fiber was once “cutting-edge” and used mostly for aerospace applications, automated production methods are making it easier to shape and form the material. It is also available in a “pre-preg” form – carbon fiber cloth that is pre-impregnated with resin allowing the manufacturer to form and cure the material into desired shapes.

Carbon fiber is mostly used for decorative purposes – “glamour panels” – for exterior components such as door panels, fenders, hoods, and roofs. It is less commonly used for “monocoque” or unibody construction on vehicles, except for specialty designs such as Formula 1 race cars. Carbon fiber is even less commonly used for parts such as brake rotors, drive shafts or wheels. As new production and molding techniques for carbon fiber become less expensive, its affordability might make it more attractive for use in the “average” automobile.

Since carbon fiber is still a relatively expensive material, it is more generally found on high-end vehicles, such as Corvettes, where the open-weave is visible on decorative (glamour) panels. The carbon-fiber component can be left in its “natural” color or painted in the car’s body color.

Repair vs. Replace
To solve the mystery of whether a repair is structural or cosmetic, it is important to understand that the standard collision shop will be making structural repairs to cosmetic carbon fiber panels. You can take a cosmetic panel that has a hole in the carbon fiber material and repair the hole – this is structural repair. A standard collision shop will be fixing the outer skin of a vehicle – a ready-to-repair type of damage - such as a scratch on the surface of a hood or a small hole in a door panel.  

As an example, if a Corvette has a visible carbon roof that is scratched, a repair can be made if the roof will be painted. With a light cosmetic scratch, the panel can be clear-coated to hide the scratch. But if the carbon fibers are torn, a repair patch would be visible and not acceptable to the customer. For replacement procedures, a mechanically fastened or bonded carbon fiber component can be replaced in the shop.

The decision to repair or replace a carbon fiber component is the same as with any metal or composite component – analyze the damage and estimate the time it will take for repair vs. the cost of a part replacement. For instance, if there is damage to a carbon fiber hood on a Shelby Mustang, a technician can spend several days recreating the hood, painting it and getting it ready for the customer. If it makes good business sense to repair the hood, rather than spend $15,000 on a new hood, then that would be the best decision. If you can do the repair, that is the key, and the answer to “repair vs. replace.”

Visibility of a repair is another factor that enters into the decision-making process for repair vs. replace. If the carbon fiber component is painted on the outside surface and the backside of the repair will not be visible, the repair can be made and should be acceptable to the customer. A visible repair would probably not be considered satisfactory.

For example, a repair made to a carbon fiber hood on a Corvette might look good from the outside after it is painted, but if you can see the patch on the underside of the hood when you open the hood, this might not be acceptable to the customer. Corvette owners want their vehicles to look good both outside and inside, so in this instance, a replacement would be preferable.

It’s Not Difficult
There are no special tools, equipment, product, or training required for repairing or replacing of a carbon fiber component. Any of the products that are currently used to repair fiber-reinforced plastics and fiberglass can be used for cosmetic repair of body panels, hoods, decks, and doors.

Some of these products include heat-set plastic panel repair adhesives, flexible and rigid foams, plastic bonding adhesives, and plastic-to-metal bonding adhesives. Consult your repair product supplier for information on which products are suitable for repairing carbon fiber parts. Your supplier will also have instruction sheets with preparation, application and finishing techniques for carbon fiber repairs.

As carbon fiber becomes a more prevalent material in car design, collision repair shops will be called upon to make repairs or replacements to these vehicles. Making structural repairs or replacing carbon fiber cosmetic panels can be a lucrative addition to your car-repair menu with the end result of satisfied customers.