基于断裂韧性预报复合材料层合板的开孔拉伸强度
Tensile strength prediction of notched composite laminates using fracture toughness

开孔层合板的强度预报往往取决于孔边的临界长度，它不仅与材料性能，而且与铺层、孔径都有关。本文基于线弹性断裂力学，提出了一种预报对称铺层层合板开孔拉伸强度的新方法，只需提供正交层合板的断裂韧性和无缺口层合板的拉伸强度，显著降低对实验数据的依赖性。首先，将临界长度表作为层合板断裂韧性和无缺口拉伸强度的函数，再通过正交层合板[90/0]8s的紧凑拉伸试验和虚拟裂纹闭合技术，确定出0°层断裂韧性，进而计算得到任意对称铺层层合板的断裂韧性。本文测试了T300/7901层合板[0/±45/90]2s和[0/±30/±60/90]s的开孔拉伸强度，孔径分别为3 mm、6 mm和9 mm。理论预报结果与试验值吻合较好，最大误差为15.2%，满足工程应用需求。 Strength prediction of a laminate with a hole generally depends on a characteristic length of the hole which is not only related to the properties of its constituent materials but also depends on the laminate lay-up and the hole diameter. In this paper, a new method based on linear elastic fracture mechanics was proposed to predict the tensile strength of a symmetric laminate with hole, which only needs the fracture toughness of a cross-ply composite plate and the tensile strength of the un-notched laminate, and which can significantly reduce the requirement on composite data. In this method, the characteristic length was first expressed as a function of the fracture toughness and the un-notched tensile strength of the laminate. Then, the fracture toughness of a 0° ply (i.e. unidirectional laminate) was determined by a compact tension test on the cross-ply laminate[90/0]8s and the virtual crack closure technique. Further, the fracture toughness of laminates with arbitrary symmetric lay-up angles can be calculated from that of the 0° ply. Tensile tests on T300/7901 notched laminates with lay-ups of[0/±45/90]2s and[0/±30/±60/90]s have been done in this work. Three kinds of hole diameters, i.e. 3 mm, 6 mm and 9 mm, were assigned for each of the laminates. The theoretical predictions for the tensile strengths are in good agreement with the measured values. The maximum difference is 15.2%, which is acceptable in engineering applications. 国家自然科学基金（11832014；11472192）；江苏省自然科学基金（BK20150479）；江苏省高校自然科学基金（15KJB130002