横衝撃を受けるCFRP板の損傷と残留曲げ強度

抄録

Damage and residual strength of [0°/90°/45°/-45°]_s graphite/epoxy composite laminated plates subjected to normal impacts were investigated experimentally. A steel ball of 10mm or 12mm in diameter was collided with the composite plate with an air gun in the velocity range of 5m/s-40m/s. Delaminations were evaluated by two methods. One was a destructive inspection using fluorescent penetrant: the impacted plate was cut off, and placed in fluorescent liquid for one night. It was then dried and peeled off lamina by lamina and ultra violet rays were projected on it. The other method was SAM (Scanning Acoustic Microscopy) which made it possible to distinguish delamination portions on different interfaces non-destructively by adjusting the focus of the acoustic lens and the gate timing for the reflected wave history. The following results were obtained: delaminations were generated only on interfaces where neighboring fiber directions are orthogonal i. e. on 1/2, 3/4, 5/6, 7/8 interfaces, where the first lamina was the impact side and the 8th lamina was the back side. The delamination areas of the interfaces which were further from the impact side were larger, i. e. 1/2<3/4<5/6<7/8. However, a damaged area distinguished on the outer surface of the 8th lamina was smaller than the delamination area on the 7/8 interface, therefore it is possible that some extent of delamination exists on the inner interface even though no damage can be recognized visually. The residual strength of impacted composite plates was evaluated by a four-point bending test. Bending strength seemed to begin to decrease at the same time that the delamination started to be generated.