Study on formability and failure modes of steel/CFRP based FMLs consisting of carbon fiber reinforced polymer prepreg and steel sheet

Due to the potential application need of the automotive and transportation industry for Fiber metal laminate parts made of steel sheets and carbon fiber reinforced polymer (i.e., Steel/CFRP based FML parts), the related combined forming process of FML parts has attracted extensive attention in the last decades. In order to design and fabricate the qualified Steel/CFRP based FML auto parts with various plane stress states, it is vital to thoroughly understand the formability and failure modes of Steel/CFRP based FMLs under various forming states and process conditions. Accordingly, in the present work, a series of deep drawing experiments were designed and conducted on Steel/CFRP based FML specimens with various width to embody their special forming features under different stress states. By considering the limit drawing height at fracture for the evaluation indicator of the forming limit of FMLs, authors studied systematically the influence of key process conditions such as lay-up scheme, stamping speed and the number of plies in the carbon fiber reinforced polymer prepreg (i.e.,CFRP prepreg) core on the formability and failure modes of FML specimens with various forming states. The research results are expected to provide a reliable data source for establishing the accurate forming limit criterion of FMLs and optimizing lay-up schemes.