Mixed-mode Fracture of a CF/PEI Composite Material

This study reports investigation on mixed-mode interlaminar fracture behavior in CFIPEI composite material based on experimental and numerical analyses. Experiments were conducted on modified Arcan specimens using the special test loading device. By varying the angle, a from 0° to 90°, mode-I, mixed-mode and mode-II data are obtained experimentally. Using the finite-element results, correction factors were applied to the CFIPEI fracture specimen. Based on experimentally measured critical loads and by the aid of the finite-element method, mixed-mode interlaminar fracture toughness for the composite under consideration has been determined. Numerical results indicate that for pure mode-I loading, mode-I stress intensity factor is maximum and as a increases, K, decreases down to 0 for pure mode-II loading. Stress intensity factor for mode-II loading shows the opposite trend; as the ratio of mode-II to mode-I increases, Kn increases. It should be noted that for loading angles close to pure mode-land pure mode-II loadings, very high ratios of strain energy release rates are dominant. As expected, it is confirmed that by varying the loading angle of Arcan specimen, pure mode-I, pure mode-II and a wide range of mixed-mode loading conditions can be created and tested.