Elastic–plastic damage of a ductile epoxy resin is investigated for the first time in the configuration of semicircular bend specimen weakened by U-shaped notches under mixed mode I/II loading conditions. U-notched specimens are prepared from the characterized epoxy material with different notch rotation angles and notch tip radii. Load-carrying capacities of the U-notched specimens are experimentally obtained by performing fracture tests under various combinations of mode I and mode II loading. The reformulated Equivalent Material Concept is employed for the polymeric material in conjunction with the maximum tangential stress and mean stress criteria to provide the theoretical predictions without any necessity for elastic–plastic analyses of their damage. Scanning electron microscopy micrographs are also taken from the fracture surfaces and utilized for realizing the micromechanical processes of damage in the tested specimens. A very good consistency is found between the experimental results and the predictions of the combined Equivalent Material Concept-maximum tangential stress criterion, as well as those of the Equivalent Material Concept-mean stress criterion.

中文翻译：

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使用两个虚拟线弹性破坏准则在混合模式 I/II 加载下缺口环氧树脂试样的弹塑性损伤预测

首次研究了在混合模式 I/II 加载条件下由 U 形缺口削弱的半圆弯曲试样的配置中韧性环氧树脂的弹塑性损伤。U 型缺口试样由具有不同缺口旋转角度和缺口尖端半径的表征环氧树脂材料制备。U 型缺口试样的承载能力是通过在 I 型和 II 型载荷的各种组合下进行断裂试验而获得的。重新制定的等效材料概念与最大切向应力和平均应力标准一起用于聚合物材料，以提供理论预测，而无需对其损坏进行弹塑性分析。扫描电子显微镜显微照片也取自断口，并用于实现测试样品中损伤的微机械过程。在实验结果与组合等效材料概念-最大切向应力准则以及等效材料概念-平均应力准则的预测之间发现了非常好的一致性。