Quasi-static fracture toughness tests were carried out on four types of beam specimens in order to determine the mixed mode I/II initiation fracture toughness of a secondary bonded laminate composed of uni-directional pultrusion composite plies. The tests included the double cantilever beam (DCB) test for pure mode I; the mixed mode end loaded split (MMELS) test for a mode I dominant mixed mode I/II ratio; the mixed mode bending (MMB) test for a mode II dominant mixed mode I/II ratio; and the calibrated end loaded split (C-ELS) test for pure mode II. Following the tests, the fracture surfaces were examined and related to the test behavior of each specimen. The results of the fracture toughness tests were used to establish a mixed mode I/II initiation fracture toughness criterion. Several criteria were examined.

为了确定由单向拉挤复合板构成的二次粘结层压板的混合模式I / II引发断裂韧性，对四种类型的梁样品进行了准静态断裂韧性测试。测试包括针对纯模式I的双悬臂梁（DCB）测试；对模式I主导的混合模式I / II比的混合模式末端加载分裂（MMELS）测试; 对模式II主导的混合模式I / II比的混合模式弯曲（MMB）测试; 以及针对纯模式II的校准末端负载分流（C-ELS）测试。测试后，检查断裂表面并与每个样品的测试行为相关。断裂韧性测试的结果用于建立混合模式I / II起始断裂韧性标准。检查了几个标准。