High Strain Rate Behaviors of Fiber Reinforced Composites in Principal and Off-Axis Directions

Materials can exhibit significantly different mechanical behaviors compared to quasi-static conditions at high strain rates (> 100 s^-1). High strain rate tests using setups such as SHPB (Split-Hopkinson Pressure Bar) can provide, in a practicable manner, the stress-strain relations for a material at high strain rates. Such properties are vitally needed for activities such as simulation-driven impact safety design of composite structures deployed in the form of automotive body parts and assembly, and other sub-systems. Although the behaviors of isotropic and ductile materials such as various metallic alloys appear to have been extensively studied and reported in literature, dependence of mechanical properties of fiber-reinforced composites especially in different off-axis directions are extremely difficult to come across. To fill up this void, a detailed experimental study has been carried out on high strain rate mechanical characterization of a laminated orthotropic glass/epoxy composite using an in-house SHPB powered by a compressed gas gun and equipped with a high speed DAQ (data acquisition) system. A unique feature of the current study is the reporting of stress-strain curves at high strain rates when specimens are loaded in off-axis directions i.e. at angles to the principal direction (viz. 0°, 15°, 30°, etc.). The results highlight the substantive effect of strain rate on properties such as failure strength of the considered composite, and its visibly distinct behaviors in various off-axis loading directions.