Characterization of High Strain Rate Dependency of 3D CFRP Materials

New composite materials are increasingly used in aviation to reduce the mass of structures. Aeronautic structures have to be designed with respect to a broad range of mechanical loadings during their operational life. These loadings are considered in the design by numerous cases, from low up to high speeds. The motivation of the presented work is to establish and characterize the high strain rate dependency of the linear behavior of composites materials. More specifically, new generations of 3D carbon/epoxy composite materials are of interest because of their high mechanical performances, which require specific experimental developments to be done. Due to the large size of their textile Unit Cell and carbon fiber high strength and stiffness, unusual dynamic test capabilities are required, which leads to revisit the test protocols, specimens definition, instrumentation and exploitation techniques. The experimental method described in this work is applied to analyze the strain rate sensitivity of the mechanical behavior of such a 3D woven composite material. The experiments are done with a servo-hydraulic testing machine (ONERA) in a strain rates range varying between 10−4 and 10 s −1. The linear mechanical behavior of the material in the warp, weft and 45∘ orientations is characterized. These tests, together with the new experimental protocol, permit to accurately reveal and measure the material behavior strain rate sensitivity, which proved to be large in the 45∘ direction.