Energy Absorption in Chopped Carbon Fiber Epoxy Composites for Automotive Crashworthiness

In the crashworthiness of automotive structures, the primary issues to the automotive industry are the overall economy and the weight of the material. To reduce the weight and improve the fuel economy, polymer composite materials have replaced more and more metal parts in vehicles. They have the added benefit of being able to dissipate large amounts of impact energy by progressive crushing. To identify and quantify the energy absorbing mechanisms in candidate automotive composite materials, test methodologies were developed for conducting progressive crush tests on composite plate specimens. The test method development and experimental set-up focused on isolating the damage modes associated with the frond formation that occurs in dynamic testing of composite tubes. Quasi-static progressive crush tests were performed to quantify the effects of specimen width, profile radius and profile constraint on the specific energy absorption and failure modes of composite plates manufactured from chopped carbon fiber (CCF) with an epoxy resin system using compression molding techniques. The carbon fiber was Toray T700 and the epoxy resin was YLA RS-35. It was demonstrated during testing that the use of a roller constraint directed the crushing process and the load deflection curves were similar to the progressive crushing of tubes. Modifications to the basic specimen geometry were required when testing material systems that have low axial stiffness to prevent a global buckling mode. The experimental data in conjunction with the test observations were used to develop analytical models for predicting the crashworthiness of automotive composite structures.