Impact Damage Resistance and Residual Property Assessment of (0/+-45/90)_s Property Assessment of (0/45/90)_s SCS-6/TIMETAL 21S

摘要

The impact damage resitance and residual mechanical properties of (0/+-45/90)_s SCS-6/TIMETAL 21S composites were evaluated. Both quasi-static indentation and drop-weight impact tests were used to investigate the impact behavior at two nominal energy levels (5.5 and 8.4 J) and to determine the onset of internal damage. Through X-ray inspection, the extent of internal damage was characterized nondestructively. The composite strength and constant-amplitude fatigue response were evaluated to assess the effects of the sustained damage. Scanning electron microscopy was used to characterize internal damage from impact in comparison to damage that occurs during mechanical loading alone. The effect of stacking sequence was examined by using specimens with the long dimension of the speciment both parallel (longitudinal) and perpendicular (transverse) to the 0deg fiber direction. Damage in the form of longitudinal and transverse cracking occurred in all longitudinal specimens tested at energies greater than 6.3 J. Similar resutls occurred in the transverse specimens tested above 5.4 J. Initial load drop, characteristic of the onset of damage, occurred o average at 6.3 J in longitudinal specimens and at 5.0 J in transverse specimens. X-ray analysis showed broken fibers in the impacted region in specimens tested at the higher impact energies. At low impact energies, visible matrix cracking may occur, but broken fibers may not. Matrix cracking was noted along fiber swims. and it appeared to depend on the surface quality of the composite. At low impact energies. little damage had been incurred by the composite and the residual strength and residual life was not greatly reduced as compared to an undamaged composite. At higher impact energies. more damage occurred and a greater effect of the impact damage was observed.