レーザー衝撃によるCFRP積層材の超高速破壊

抄録

We performed hyper-velocity impact tests that laser-accelerated aluminum flyer collided to carbon fiber reinforced plastics (CFRP) target. A short-pulsed intense laser beam can accelerate a small flyer as fast as LEO (low earth orbit) satellite velocity. We succeeded in observing the deformation and fracture behavior of the CFRP target with a high-speed framing camera. After the impact experiments, we investigated damages of the CFRP target with an optical microscope and a scanning electron microscope (SEM). As these results, the hyper-velocity impact fracture mechanism of CFRP was proposed as follows: (1) Under the impact back surface, spallations are caused by reflected tensile waves and the similar surfaces of the crack-opening mode I fracture are created. (2) The spalling cracks propagate along the direction of carbon fibers and produce the fracture surfaces of mode II or mixed-mode I/II. (3) At the center of the spalling layer, carbon fibers are kinked and broken by tension. For the lower laser energy, the above damages could not extend to carbon fiber breakage. On the basis of the fracture mechanism, we assembled a model for numerical analyses. Using the LS-DYNA3D, we conducted numerical simulation of the hyper-velocity impact tests. Displacement and velocity at back surface of the CFRP target calculated in the numerical analyses agreed comparably well with the results of the experiments.