Strain energy release rate (SERR) along a linear crack front of a multidirectional composite DCB specimen shows an obviously non-uniform distribution, which causes the fracture toughness G_Iavg measured by experiments smaller than the real G_IC, and so leading to a lower estimation of fracture toughness. In this study, based on the numerical model a novel semi-empirical closed-form formula was proposed for determination of pure mode I fracture toughness of a multidirectional composite DCB specimen via a width-wise non-uniform distribution parameter. These expressions translate the relationships between the width-wise non-uniform distribution ratio and the specimen width as well as the material parameters. They provide a rapid method to measure correctly the pure mode I fracture toughness of an uncoupled multidirectional composite DCB specimen by integrating the effect of non-uniform distribution of the strain energy release rate at the crack front.

多向复合材料 DCB 试样沿线性裂纹前沿的应变能释放率 (SERR) 呈现明显的不均匀分布，导致实验测得的断裂韧度G _Iavg小于实际G _IC，因此导致对断裂韧性的估计较低。在本研究中，基于数值模型，提出了一种新的半经验闭式公式，用于通过宽度方向非均匀分布参数确定多方向复合 DCB 试样的纯 I 型断裂韧性。这些表达式转换了宽度方向的非均匀分布比与试样宽度以及材料参数之间的关系。它们提供了一种快速方法，通过整合裂纹前沿应变能释放率的非均匀分布的影响，正确测量非耦合多向复合 DCB 试样的纯 I 型断裂韧性。