Impact-Induced Delaminations in Thermoset and Thermoplastic Composites

Abstract

In this work ultrasonic NDE is used to address three problems in impact-induced delamination. First, quantitative correlation between the energy dissipated in the laminate and the total area of delamination is investigated. The results are compared to mechanica1 properties of the composite, such as the fracture toughness. Second, the ability of a delamination to block the passage of ultrasound and the associate "shadowing" effects are studied. Finally the impact resistance in terms of the area of delamination per unit of dissipated energy is compared for a thermoset and a thermoplastic composite. A number of composite systems have been studied in this work, including carbon-epoxy (C/EP), carbon-polypheny1ene sulfide (C/PPS), and glass-epoxy (G/EP). Here we use the terms carbon-epoxy and graphite-epoxy interchangeably. Both woven laminates and laminates made of unidirectional prepreg tapes have been investigated. Ultrasonic nondestructive resu1ts were compared with destructive tests such as pyrolytic de-ply.