Delamination characteristics of double-cantilever beam and end-notched flexure composite specimens

Abstract

The distributions of strain energy release rate, G, at the crack fronts of double-cantilever beam (DCB) and end-notched flexure (ENF) specimens have been analysed by means of the plate finite element. A boundary layer phenomenon in the distribution of G at the crack front is found. The applicability of beam theories as data reduction tools for DCB testing is examined. The effect of a curved crack front on the use of beam theories in the calculation of strain energy release rate for a DCB specimen is also discussed. Except for unidirectional and cross-ply laminates, the distribution of strain energy release rate at the crack front is found to be skewed, and a parameter is introduced to measure this skewness. Recommendations on DCB specimen design are made for the fracture toughness test to minimize the non-uniform and skewness effect. Finally, it is found that the boundary layer effect in the ENF specimen is not as severe as that in the DCB specimen.