Analysis of composite ENF specimen using higher order beam theories

Mathematical modelling, for the stress analysis of symmetric composite end notch flexure (ENF) specimen, has been presented using classical beam theory, first, second, and third order shear deformation beam theories to determine the strain energy release rate (SERR) for symmetric composites under mode II interlaminar fracture. In the present formulation, appropriate matching conditions have been applied at the crack tip and these matching conditions at the crack tip have been derived by enforcing the displacement continuity at the crack tip in conjunction with the variational equation. Compliance method has been used to calculate the SERR. Beam models under plane stress and plane strain conditions agree with each other with good performance to analyze the unidirectional and cross-ply composite ENF specimens, whereas for multidirectional composite ENF specimen, only the beam model under plane strain condition appears to be applicable with moderate performance. Third order shear deformation beam model of ENF specimen has been found to be better than other beam models in determining the SERR for unidirectional, cross-ply and multidirectional composites under mode II interlaminar fracture.