Experimental method for mode I fracture toughness of composite laminates using wedge loaded double cantilever beam specimens

This study proposes a simple and accurate data reduction scheme for the wedge loaded double cantilever beam (DCB) specimen. The effects of axial loading applied by wedges were considered for the evaluation of mode I energy release rate. Furthermore, a methodology for the determination of crack length during the tests was proposed. The presented method was verified by both finite-element (FE) analyses and fracture toughness tests. The results of the FE analyses showed that the mode I energy release rate obtained by the presented method well agreed with that obtained by the virtual crack closure method. Both the wedge loaded DCB and standard DCB tests were carried out to verify the presented method with unidirectional carbon fiber reinforced composites. Mode I fracture toughness obtained by the wedge loaded DCB tests was almost identical to that obtained by the standard DCB tests.