SMC (Sheet Molding Compound) works well for heavy duty truck parts, especially ones requiring complexity, strength, and impact resistance. One of the projects I am working on is a heavy truck with these SMC parts, including a hood and a driver”s and passenger”s truck fender extensions. Each of these SMC parts is very complex in geometry because of its complex application. The following is a picture of one of the SMC fender extensions.
This SMC part is all one single molded piece, having very complicated geometry. It can also be noted that there are not any undercuts, i.e. the mold can open and close without having to move around the part. It has a mostly constant cross section, is not supported by any metal struts, and is attached to the cab by three bolts. The geometry and details to match the cab and hood styling are molded-in so that the part can be painted and bolted on the truck.
If a part needing this much complexity was manufactured with sheetmetal, it would have many more pieces of the assembly and much more bracing. Metal would also not have the resistance to corrosion and impact that is enjoyed by this composite part.
This fender extension is from a truck that has been on the road since 1993, with over 270,000 miles on it. This part has been in the wild for over 15 years, and has been exposed to tons of road salt, debris from the tires, and lots of other environmental exposures. It has survived well, only needing an update in paint to refresh its look.
Another great application of composites!