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3mm、6mm和9mm。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.