Determination of mode I interlaminar fracture toughness of composite by a wedge-insert double cantilever beam and the nonlinear J integral

Abstract Wedge-insert double cantilever beam (WDCB) is a promising test specimen for measuring the mode I fracture toughness of composite material subjected to impact and static loadings. However, it is considerably more challenging to determine the energy release rate and fracture toughness of WDCB than those of double cantilever beam (DCB) because the effective bending arms of WDCB strongly depend on the crack opening displacement. In this paper, exact and explicit energy release rate of a composite WDCB was derived by using the nonlinear J integral to consider the effects of large deformation and axial force. Compared to the alternative data reduction methods, the proposed J integral method is simpler and more accurate for measuring the mode I interlaminar fracture toughness of composite, especially for largely deformed WDCB.