Investigation of the mechanical behavior of CARALL FML at high strain rate

摘要

Fiber metal laminates (FMLs) are hybrid composite structures made of thin sheets of metal alloys and plies of polymeric materials reinforced with fibers. Among various FML, CArbon Fiber Reinforced ALuminum Laminates (CARALLs) are appreciated because of their excellent impact resistance and energy absorption property; for the correct design of components that are intended to exploit such capabilities, the mechanical characterization is very important, not only in quasi-static but also in high strain rate conditions. With this regard, CARALL has received less attention if compared with other FMLs; moreover, conflicting results are found in the literature, as the actual properties depend on a number of parameters. Each type of FML requires a dedicated test campaign for a correct characterization.Hence, this work shows the mechanical characterization of a newly developed CARALL, manufactured in the laboratories of the Wayne State University, that makes no use of adhesives film among layers. Quasi-static and dynamic tensile tests have been carried out on CARALL sheet samples.The dynamic tests were made by a direct version of Split Hopkinson Bar (SHB) at an average strain rate of 300 s(-1); in the work, the difficulty of achieving accurate strain measurements in such tests was also analyzed, concluding that a direct strain measure by image analysis is essential. A finite element model was also used to confirm the validity of the adopted approach.Finally, the specific CARALL here considered is not strain rate sensitive in terms of material strength; on the contrary, it shows a different failure mode if subjected to dynamic rather than quasi-static loading.