Measurement of initiation values of GIC in IM6/PEEK composites

Abstract The double cantilever beam (DCB) specimen is widely used to determine delamination resistance under mode I loading. However, recent work has indicated the geometry-dependence of values of G IC measured during propagation of a delamination in unidirectional specimens of IM6/PEEK when fibre bridging and multiple cracking are observed. An alternative approach is to quote initiation values of G IC , but little information is available to allow a rational test procedure to be proposed. In this paper the influence of different types of starter defect on the initiation values of G IC in IM6/PEEK is examined. This has enabled a suitable starter defect type to be identified. Finally, results from static fatigue tests are presented which indicate a self-toughening mechanism in this material.