Impact compression properties of three-dimensional five directional carbon fiber/epoxy resin braided composite circular tubes at elevated temperatures

Three-dimensional five-directional (3D5D) carbon fiber/epoxy resin braided composite circular tubes were prepared by using 1×1 four - step circular braiding technology and resin transfer molding (RTM) process. Axial impact compression tests of the 3D5D carbon fiber/epoxy resin braided composite circular tubes were carried out using a split Hopkinson pressure bar (SHPB) equipped with a high-temperature device in environments of ambient temperature (20℃) and elevated temperature fields (80℃, 110℃, 140℃, 170℃). According to the experimental results, the coupled effects of temperature and strain rate on the impact compression performance and failure behavior of the 3D5D carbon fiber/epoxy resin braided composite circular tubes were revealed. Macroscopic and microscopic morphology observations and analyses of the specimens after impact compression failure were performed by combining a stereo microscope and a scanning electron microscope (SEM). The research results show that the mechanical properties of 3D5D carbon fiber/epoxy resin braided composite circular tubes are significantly affected by the temperature and strain rate. At ambient temperature, the impact compression performance of the 3D5D carbon fiber/epoxy resin braided composite circular tubes is stable, and the increase of strain rate can improve the mechanical properties such as compressive strength and compressive modulus of the material. The failure mode is mainly fiber breakage. In elevated temperature field, the mechanical properties of the material decrease. The impact compression resistance decreases with increasing temperature. The failure modes include resin softening and fiber - resin interface debonding. The influence of the strain rate on the mechanical properties will change due to high temperature interference.