Development of a standardized procedure for the characterization of interlaminar delamination propagation in advanced composites under fatigue mode I loading conditions

A round robin exercise on opening mode I fatigue delamination propagation has been performed with the aim of developing a standardized test procedure. The material chosen for the test was one type of carbon–fiber reinforced polymer–matrix laminate (IM7 fiber, 977-2 epoxy). The Double Cantilever Beam specimen from the quasi-static mode I delamination resistance test (ISO 15024) has been used for the fatigue test. Test set-up, measurements and data acquisition have been defined with an emphasis on applicability in an industrial test environment. Selected test parameters have been varied in order to investigate their effect on the results. Three different approaches for delamination length determination have been compared. Visual determination of delamination length, a compliance-based approach and an effective delamination length calculation based on a separate measurement of the modulus of elasticity yield reasonable agreement. This agreement suggests that further development of the test procedure to incorporate automated data acquisition and analysis may be worthwhile.