Toughening of Graphite-Epoxy Composites by Interlaminar Perforated Mylar® Films

摘要

Fracture and notch-strength tests of graphite-epoxy composites have shown that unidirectional lay-ups generally exhibit longitudinal cracking before fail¬ure, whereas multidirectional lay-ups fail transversely with little longitudinal cracking. A simple qualitative analysis suggested that the higher matrix shear stresses in unidirectional materials cause the longitudinal cracking, and that this cracking is responsible for the higher toughness of unidirectional com-posites. In a series of comparative tests, the interlaminar strength of multi¬directional composites was reduced by placing perforated Mylar films between laminae;tests on notched and slotted specimens showed that the interlaminar films promoted delamination and longitudinal cracking near the notches and that, as a result, toughness, notch strength, and impact strength were substantially increased.