A simple technique for measuring mode I delamination energy release rate in polymeric composites

Abstract

A simple technique is developed to evaluate the mode I delamination energy release rate ( G 1 ) in unidirectional polymeric composites. The technique involves growing the delamination crack in a unidirectional double cantilevered beam (DCB) specimen by controlling the crack mouth deflection with a small diameter cylindrical rod. Both the critical mode I delamination initiation energy release rate ( G c ) and the delamination arrest energy release rate ( G Ia ) can be evaluated using this approach. The specific energy release rate to be determined depends on the delamination growth behavior of the composite material. For a unidirectional graphite-fiber-reinforced thermoplastic composite, namely polyetheretherketone (PEEK) system, both G Ic and G Ia were evaluated using the same technique. For a unidirectional glass-fiber-reinforced polyester composite, G Ic was evaluated using the proposed technique. Results from this new technique compare very well with the results from conventional DCB testing. Also, the new technique allows the evaluation of critical delamination energy release rate in adverse environment since it does not require specimen end-tabs or hinges. Thus, adhesive failure at high temperatures or in hot-wet conditions will no longer be a concern.