Comparison of coupon and full-scale determination of energy release rate for bonded composite repairs of pressure equipment

Abstract

Bonded composite repairs of pressure equipment intended to rehabilitate a through-wall defect are governed by the fracture resistance of interface between the composite and the substrate. This fracture-dominated failure mode requires a detailed understanding of the fracture energy of the composite–substrate interface. Current approaches for measuring this interfacial fracture energy use simulated repairs on small-scale pressure vessels. In this paper we describe a simple coupon-based test using a width-tapered-double-cantilevered beam specimen. Fracture energies determined using the coupon-based approach were in close agreement with values back calculated from full-scale testing performed on simulated through-wall defects.