Investigation of Damage Tolerance of Graphite/Epoxy Structures and Related Design Implications.

This investigation was undertaken to evaluate the damage tolerance of typical graphiteepoxy structure to service damage. AS3501 graphiteepoxy I-stiffened panels and honeycomb panels were fabricated and its tolerance to low-velocity impacts was measured. Three impact threats were investigated runway stones, a blunt impactor with a tip radius of 0.64cm 14 inch, and a blunt impactor with a tip radius of 2.54cm 1 inch. Impact parameters were selected that would just cause visual damage. This worked well for the runway stones, but for the tests of the one-inch penetrator on the honeycomb panels visual damage was not easily observed. C-scan damage was, however, easily detectable. Residual strength specimens were cut from the damaged panels and tested. The specimens contained damage at levels of 70, 100, 130 of the level to cause visual or C-scandamage.