Investigation of fracture criterion for composite using CTS specimen

The interlaminar fracture behavior of a unidirectional carbon fiber reinforced composite under full range of in-plane loading conditions has been investigated. Loading conditions from pure mode I through various mixed mode I/II ratios up to pure mode II have been generated by the aid of the compound version of the compact tension shear (CTS) specimen. From the experimentally measured critical loads the mode I, mode II and the various mixed mode I/II critical energy release rates at crack initiation have been determined by the aid of the finite element method and the modified virtual crack closure integral method. Based on these results the parameters of a fracture criterion for the composite under consideration have been determined. It was shown that for the present carbon/epoxy composite the best approximation is achieved employing in criterion a linear function.