Characterization of Mode-I fracture of hybrid material interface bonds by contoured DCB specimens

Abstract

An engineering approach for evaluating the opening-mode (Mode-I) fracture toughness of hybrid material interface bonds is presented. A contoured double cantilever beam (CDCB) specimen is designed by the Rayleigh-Ritz method and used for fracture toughness tests of bonded interfaces. The specimen is contoured to achieved a constant rate of compliance change with respect to crack length, and the linearity of the compliance crack-length relationship of CDCB specimens is verified using Rayleigh-Ritz and finite element models. The numerical and experimental study on the linearity of the compliance rate change indicates that a constant-taper CDCB specimen can be used with reasonable confidence for Mode-I fracture toughness tests of bonded interfaces. Mode-I fracture tests are performed using constant-taper CDCB specimens for wood-wood and FRP-wood bonded interfaces to determine the critical loads for crack initiation and crack arrest, from which the respective critical strain energy release rates are obtained. The Jacobian derivative method (JDM), a finite element post-processing algorithm, is adopted to predict the strain energy release rate of the CDCB test specimens, and the predictions match closely with experimental results.