Mechanical behaviors of the carbon fiber reinforced X-core sandwich structure under the dynamic compression

A split Hopkinson pressure bar technique was applied to investigate the dynamic response of carbon fiber composite sandwich structures with the X-cores. The compressive mechanical behaviors of the composite X-core unit cells and its foam reinforced unit cells at the strain rates ranging from 3 & BULL;10-4 s- 1 to 600 s-1 were obtained. During the dynamic tests, the dynamic stress equilibrium state in the unit cells was achieved by adopting the pulse sharpers and discussed comprehensively. The measured structural strength increased by 81.9 % on average at the high strain rates than that under the quasi-static compression. Under the dynamic compression, the failure modes captured by a high-speed camera were found similar with that of the quasi-static tests. Finite element analysis was utilized to study the variation history of stress and strain rate fields of the core. Because of the material failure strain enhancement effect, the experimental and simulated compressive strength of the com-posite unit cells both increased significantly at the high strain rates. At the same high-speed compressive strain rate, the dynamic reinforcement effect of the composite sandwich unit cell was smaller than that of the parent material.