Effects of Large Deflection on Mode II Fracture Test of Composite Materials

Abstract

Large deflection response and its effect on measuring the Mode II fracture toughness of composites have been studied for the End-Loaded-Split (ELS) test. The response is analyzed by nonlinear beam theory and the correction to toughness calculation based on linear beam theory is obtained for any crack length. The effect of large deflection on accuracy of load measurement is also studied. In addition, the ELS test is used to measure the Mode II toughness of carbon fiber/polyetheretherketone (PEEK) composite. It is found that the data reduction procedure based on linear beam theory needs to be corrected if the fracture occurs at large deflections. Special care should also be taken towards a valid load measurement when using the ELS test in the large deflection range.