The Age of Automotive Composites

Jan. 1, 2020
In the late 1930s and into the 1940s, fiberglass or FRP was available — but only being considered in very limited applications. Although one of the OEMs considered making deck lids of fiberglass in the late 1930s and early 1940s, they returned

Composites are giving engineers design freedom and shops new challenges

In the late 1930s and into the 1940s, fiberglass or FRP was available — but only being considered in very limited applications. Although one of the OEMs considered making deck lids of fiberglass in the late 1930s and early 1940s, they returned to sheet metal mainly because the molding and production process was done exclusively by hand lay-up.

By the late 1940s and into the 1950s, the process of molding fiberglass had made some serious improvements. In fact, in 1953, General Motors was able to introduce the first all fiberglass body vehicle, the Corvette. During the 1950s and 1960s, the Corvette was the main use of fiberglass with a few manufacturers using fiberglass for fender or quarter panel extensions. The "enduro" bumper was developed in the 1960s and was designed to take a minor hit with little or no damage.

During the 1970s, the industry began to use plastic composite bumper covers or "fascias" in somewhat limited quantities. Today, almost all cars worldwide use composite bumper covers or fascias. Then in the early 1980s, the OEMs switched from fiberglass or FRP to a new material called Sheet Molded Compound or SMC. This material had actually been used since 1973 in some header panels. The repair industry was fixing the "new fiberglass" and experiencing a great deal of repair failures. Most in the industry assumed this material was fiberglass and tried to repair it like fiberglass. However, SMC has a very different chemical makeup and needs to be repaired with the appropriate repair material. This marked the start of the new age of automotive composites.

The trend to composites

Plastic composites are a growing trend in vehicle manufacturing. For example, the glass headlamp is now a module made of plastic composites and adhesive. Today, several hoods are changing from metal to SMC. The enduro bumper that was introduced in the 1960s evolved into the flexible fascia on today's cars and the International Standards Organization codes have molded in these covers, TPO, TPE.PP and EPDM etc. This leaves many repair technicians wondering why there are so many types of composites.

Simply, with the amount of plastic composites available growing almost daily, this gives the automotive design engineer a tremendous amount of freedom. These materials afford the engineer the ability to change the appearance of an automobile with little effort in a short amount of time.

With all of this in mind, it's important to accept that plastic composite — when used in an appropriate application — is an improvement over the parts once made of glass and metal. Today's automotive design engineer has the composite materials available to create a lighter and more durable hood, as well as a door outer panel that can take a shopping cart bump without a dent. And let's not forget that it won't rust. This is possible through the use of sheet-molded compound.

Further, there is a new material coming into the picture – carbon fiber — that is being used on exotic cars and some limited use on low production cars. The Corvette has used fiberglass, SMC and now is using a carbon fiber hood along with other composites. As far as repairing this material, repair professionals deal with them much the same as SMC.

Composites also appear on the side of today's vehicle called cladding — large side moldings made of the same materials as the fascias, TOP, TPE and PP. A vehicle that normally had a fairly smooth and plain side can take on a completely new appearance with cladding added to the side of the vehicle. These parts or claddings can serve two or more purposes — changing the appearance of the side of the vehicle and stone chip protection to the lower portion of the doors and rockers.

DaimlerChrysler uses cladding on the Grand Cherokee; Ford is adding cladding to the Explorer and Excursion; Chevrolet pickup trucks have large wheel opening moldings or flairs made of some composite type that will protect from stone chipping. Shops can repair these parts in the same manner as bumper covers. Although some of these have textured finishes, most are smooth-finished.

Reparability of composites

With an understanding of why the OEM manufacturers have increased the use of composites in today's automobiles, it is important to understand how and when to repair these materials.

Whether or not the part should be repaired depends on two factors. First, decide whether the part is worth fixing. The decision to repair or replace a composite is made the same way as it is for any other part on the vehicle — compare the amount of damage versus the cost of the part. Second, determine if the technician has the training to make a quality repair.

Any composite being used on an automobile today can be repaired. Not too many years ago, you needed anywhere from five to eight products sitting on the shelf just to address bumper cover repair. With the demand for simplicity placed on the adhesive repair material companies, the materials needed on hand have been reduced to one or two products on the shelf. The OEMs are leaning in the direction of specification-based repair and repair materials that meet a spec set by the automobile manufacturer, which can reduce the opportunity for failed repairs to a minimum.

The repair of composites though is unique. For example, SMC and carbon fiber composites are fiber rich materials. As such, a backing patch can't be put on the backside and simply fill the front or cosmetic side with body filler because of thermal expansion and contraction. If you have a fiber-rich part and you do a resin rich repair in the middle of that part, you can't expect the repair area to expand and contract at the same rate as that part. You must control the repair area by using a repair adhesive made for SMC repair and packing as much fiberglass cloth into the repair as you can. This will simulate the fiber rich part, which will expand and contract similar to the original material. When this is not done, a bullseye or halo effect results a few weeks after the repair is completed.

There are a few situations that may make fiber-rich parts not repairable since the fibers in these materials are not 100 percent saturated with resin. This can be an issue if the part has been contaminated with an outside substance. Consider a moderate front-end accident on a vehicle with an SMC hood. The hood sustains minimal damage but the core support is damaged, severing one of the air-conditioning high-pressure lines. The Freon escapes, wetting down the SMC, and it also carries the lubricating oils to the backside of the SMC and the fibers "wick" the oil in. Even though the damage to the hood was minimal, it may not be repairable due to this saturation.

Another issue that can cause a nonrepairable situation is the use of silicone-based products such as interior dressings. Some owners of show cars will spray the engine compartment with these products for that shiny look under the hood. However, this results in silicone leaching into the SMC.

Bumper cover repairs have become very simple over the past few years. Many covers are unnecessarily scrapped that could be saved with minor repairs. One of the most repairable parts of a cover is the mounting tab. Side cladding is made of the same composites as bumper covers, so the above is true for it as well. Further, there are now composite pick-up beds on the market — some made of SMC and others made of S-RIM or R-RIM. These materials will be repaired similar to SMC.

The future of composites

The amount of plastic composites used in vehicles is increasing and new composites continue to be developed. Be sure to further your repair training and be aware of changes in vehicle construction to ensure success.

Ed Staquet, Technical Support Manager for LORD Corp., is a 40-year veteran of the auto body industry who joined LORD in 1992. A member of the I-CAR Hall of Fame, he is well known in the industry for his training efforts and is a Gold Class trainer for I-CAR. He is currently in his second term on the I-CAR International Board of Directors.

Sponsored Recommendations

Best Body Shop and the 360-Degree-Concept

Spanesi ‘360-Degree-Concept’ Enables Kansas Body Shop to Complete High-Quality Repairs

How Fender Bender Operator of the Year, Morrow Collision Center, Achieves Their Spot-On Measurements

Learn how Fender Bender Operator of the Year, Morrison Collision Center, equipped their new collision facility with “sleek and modern” equipment and tools from Spanesi Americas...

ADAS Applications: What They Are & What They Do

Learn how ADAS utilizes sensors such as radar, sonar, lidar and cameras to perceive the world around the vehicle, and either provide critical information to the driver or take...

Coach Works implements the Spanesi Touch system

Coach Works Uses Spanesi Equipment to Ensure a Safe and Proper Repair for Customers