Generation of mixed mode I/II failure criteria from MMB specimens: an experimental study

Characterization of resistance to delamination is of great importance in selection of composite material. Mixed mode delamination is one of the most serious failure modes in aerospace composites. This article examines the delamination behaviour of mixed mode bending (MMB) test specimens made of glass/epoxy and carbon/epoxy composites. Literature published test data on different composites have been utilzed to identify the best suited failure criterion. Benzeggagh-Kenane (B-K) criterion as well as the polynomial criteria are used to generate failure envelopes from the fracture toughness data of composite specimens. Experiments were conducted on unidirectional fiber reinforced epoxy MMB specimens to analyze the failure trend of laminated composites and to validate the proposed polynomial criteria. Present investigations reveal that both B-K and polynomial criteria fit well for unidirectional specimens and cubic polynomial criterion fits well for angle-ply specimens. (paper)