ポリカーボネートにおける超高速衝突損傷の進展挙動評価

抄録

Hypervelocity-impact experiments have been performed on polycarbonate to investigate the impact-induced damage process progressing inside polymer material. The damage evolution and stress-wave propagation associated with hypervelocity impact have been observed by means of the two-directional (side-view and rear-view) scattered light imaging using two ultra-high-speed cameras. The obtained time-resolved images offer the information about the three-dimensional time evolutions of not only stress wave propagation and damage development but also damage texture which is not obtained in shadow graph. Under the 4.99 km/s impact of an alumina ceramics sphere, the alumina impactor is fractured at impact moment and the lump of impactor-fragments penetrates into polycarbonate with its collapsing. The stress wave generated by the impact propagates into target and reflects on the rear surface as the rarefaction wave. This wave induces spall fracture inside polycarbonate. After some development of spall fracture, a stress wave propagates from the spall plane. Compering the side-view and rear-view images, this stress-wave generation is considered to be tensile-stress-release from the free-surface plane formed by spallation.