Technical: Carbon Fiber – More Challenges on the Horizon

Technical: Carbon Fiber – More Challenges on the Horizon

Automakers are continually turning to lighter materials to hit government fuel efficiency standards. That's why we may see more carbon fiber in the future.
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Photos courtesy of Abaris Training (www.abaris.com)

Change keeps coming to the collision repair industry. That’s a given, as automakers are still scrambling to find ways to meet the government CAFÉ standard of 54.5 mpg by 2025. This requires car manufacturers to improve fuel economy by at least 50 percent across vehicle passenger models, which is driving them to find much stronger and lighter materials. We know aluminum will increase in use, but other materials are being sought to decrease weight as well.

Carbon Fiber

Carbon fiber’s strength is impressive. It’s thinner than a human hair and stronger than steel. Its ability to form angles and lines is also appealing. Being able to make larger and stronger panels to reduce the number of parts to assemble also adds to its appeal. Recent discoveries of cheaper ways to make carbon fiber show that the automakers really want more of it.

The problem we run into with carbon fiber is similar to what happened with aluminum. It’s a great material and lightweight but is somewhat expensive to use. Other discussions revolve around stress loads and softening. Metals can be weakened over the repeated stresses of driving and or crash-related issues. These stresses can be hard to detect and can become problematic over time. Finding a material that has less stress-related issues but lightweight leads engineers to look to different materials.

Many Applications

Carbon fiber or CFRP has been used for years in many applications. Aerospace racing and other ventures have used carbon fiber with great success. Even repair procedures are improving. The problem with using carbon fiber is the expense and time in manufacturing. To reduce these expenses, manufacturers are finding new ways to reduce the cost. BMW pushed in that direction to integrate carbon fiber into the i-series. This shows promise and is leading to the use of carbon fiber doubling in the near future. Doubling to what’s currently being used is not a big leap. Over time and with more cross metals being used to try to lower cost, we may see much more use.

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Repair Industry

When Ford introduced the F-150, it presented challenges in getting training and equipment to repair mainstream vehicles, which has led shops to have reservations about making the move. Will the investment in training and equipment pay off? Where will the return on investment (ROI) be?

Carbon fiber repair procedures are not widely known or talked about. I-CAR has training that’s great for getting to know what repairing some parts entails. BMW has been open about the repair of the i3 and has shown that part replacement of sections is relatively straightforward. Many are waiting to see what the cost of equipment and training will be. With margins getting smaller, shops are struggling with costs. Adding more costs to repair carbon fiber is a hard issue to deal with. Add in all the electronics inundating repair shops and it seems like an even more daunting task.

Part Replacement

Mechanically fastened panels are easy for repairs as they’re pre-made and ready to go. Refinishing is also straightforward. When an industry is not equipped to handle new technology or repair that technology, we turn to a “replace what is damaged” process.

On the scale of use on current high-end models of cars, remove and replace will be the norm. Even with the high cost of replacement of these parts, there is little economic incentive to repair damaged parts. It’s easier to do than repair and can be the only alternative. This creates a dilemma for the insurance industry. Currently, carbon fiber is expensive to manufacture. Replacement is quick, but this process may bring vehicle repair costs up. Learning to repair may be the best option for shops and insurers. The trick is to make it an incentive to do so. This also is in vehicle manufacturers’ best interest, too. We’ve seen the costs associated to replace panels on the carbon fiber Corvette. These costs are passed on to the owners and all of us through insurance rates.

Structural Repair

As CFRP becomes a more viable material for uses other than just panels, the repair side must be addressed as the structural components will require repair. These repairs currently are being done mostly by dealers. If carbon fiber makes it into the mainstream, shops will need to adjust.

Structural repair has taken many forms for vehicle manufacturers, from BMW offering sections of structural parts to “Flying Doctors” or specialists who fly in to dealers to repair their vehicles. This has led to a lot of confusion as to how to diagnose and repair CFRP.

Understanding and repairing structural parts can be done at section points where pieces are joined. Partial replacement has long been used in automotive repair. When full pieces are manufactured, then sectioning becomes an issue. The knowledge on how to diagnose repair and complete repairs becomes necessary. Damage analysis along with understanding repair methods may take very specialized training.

As more shops gain experience at plastics through bumper repair, the repair materials used may be more familiar than we know. Companies such as 3M and Pliogrip are heavily involved in the production and repair of CFRP. There’s a great deal of similarity as carbon fiber is a reinforced plastic. The use of adhesives and rivets or other mechanical fasteners helping to secure panels is also similar to what we’re learning today.

Exposed vs. Non-Exposed

Two types of carbon fiber should be addressed. The first is exposed weave carbon fiber such as the roofs on Corvettes. Unlike fiberglass, it’s a woven blanket with a pattern that actually allows the transmittance of light. The carbon fiber blanket is encased in resin, which can be clear or tinted. The repair of these panels is a superficial repair, if it can be done at all. Somewhere along the line of manufacturing and development, someone made a clear piece to show how the weave blanket of fibers lays in. Somebody else or even the same person thought this looked cool. I agree, and so was born the exposed weave carbon fiber. You’ll find it difficult to repair as the continuous weave can’t be spliced effectively, leaving a line or distortion.

Non-exposed is basically the same but painted, and is easier to repair as the repairs will be under the finish. A patch system even similar to SMC repair could be used if approved by the car maker. This can be done if the panel is still structurally sound, meaning the damage does not extend to the edge. If the damage does extend to the edge, then a different approach will be required. This will involve some interesting procedures.

The best way to see these procedures is to take the I-CAR online course. The use of frozen, pre-permeated layers and pressure along with vacuum and heat is very interesting. The completed repair gives the panel its structural integrity. The process is time-consuming, so a shop will spend a great deal of effort to complete this kind of repair.

The Future

The future of carbon fiber is uncertain as no one can predict a breakthrough in engine, metal or carbon fiber manufacturing. Vehicle manufacturers will continue to find the magical cure to the CAFÉ standards. Trying to keep it affordable is a challenge.

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