2018 年 84 巻 863 号 p. 18-00012
With the development of spacecraft, the brittle materials like ceramics and glass have been used for significant components especially in optical and thermal systems. However, they are vulnerable to damage by hypervelocity impact of space debris and micrometeoroids. Against a backdrop of increasing number of space debris, impact-damage evaluation on brittle materials become a growing concern. In this study, a series of hypervelocity impact experiments has been conducted to evaluate internal damage propagation mechanism in a fused-silica-glass plate target by impacting a stainless steel projectile with 1-mm diameter in the velocity range around 2 km/s. Damage propagation behavior was observed from two directions simultaneously by means of in-situ shadowgraph coupled with an ultra-high-speed video camera. The observation concentrates on propagation behavior of lateral cracks and that of internal failure. The former is revealed to a mass of small cracks which were generated by passing of the surface stress wave. The latter propagation is affected by the longitudinal and transversal waves, the reflection of the spherical stress waves on the back surface of target. The failure propagates rapidly two times by the reflected waves: first rapid propagation was caused by tensile stress induced by the reflected longitudinal wave, the secondary rapid propagation was caused by shear-compression mixture stress induced by the reflected transversal wave, which was generated by mode conversion of the longitudinal wave.