Dynamic crush response of compression molded planar isotropic carbon fiber reinforced composites

Abstract Vehicle mass reduction can be achieved through the utilization of carbon fiber reinforced composites within the vehicle body structure. In this study, planar isotropic compression molded carbon fiber reinforced composites are studied for their potential utilization as automotive primary energy absorbing structures. The energy absorption behavior of a discontinuous randomly oriented 2‐D planar isotropic carbon fiber reinforced nylon 6 thermoplastic composite and a continuous 2 × 2 twill quasi‐isotropic carbon fiber reinforced epoxy thermoset composite are studied by dynamic flat plaque crush testing. Post‐mortem failure modes of both materials are related back to their load‐displacement and energy‐displacement curves under different test conditions. It is shown that crush fixture support length dictates the failure mode and specific energy absorption (SEA) of all fiber reinforced composites tested. In addition, elevated temperature testing of the nylon 6 carbon fiber reinforced composites reduces the SEA in all test configurations. Finally, an automotive carbon fiber composite front end energy absorbing structure is considered as the replacement over a legacy metallic energy absorbing structure. Mass reduction benefits beyond the improved SEA of the composite as compared to the metallic structure it replaces are discussed by considering the increased crush length efficiency of the composite structure which can reduce the vehicle front end length, and therefore the mass of the vehicle. These results are expected to direct the future development of fiber reinforced composites structures in energy absorbing automotive structures.