含孔CFRP正交层合板的双轴拉伸力学行为

摘要

The biaxial tensile mechanical properties of carbon fiber reinforced polymer (CFRP) cross-ply composite laminates with central hole were experimentally studied using the uniform thickness cruciform specimens with slots in the arms.Three biaxial load ratios were applied to study the effects of load ratio on the biaxial tensile strength and failure characteristics of CFRP cross-ply laminates.The results show that under the biaxial tensile loads, the interfaces between the plies with fibers cut off and their adjacent plies with continuous fibers are prone to delaminate, and resulting in the reduction of load bearing capacity of CFRP cross-ply laminate.Under an equal biaxial tensile load, the cracks initiate at the matrix between the cutting-off and the continuous fibers along the hole edge, resulting from the combined load of the transverse tension and longitudinal shear.Under an unequal biaxial tensile load, matrix crack initiates in the plies perpendicular to the load direction with a higher tensile velocity, and appears at the hole edge with a high stress concentration.With the increasing of the load ratios, the microstructure damage in the regions with a higher tensile velocity develops more rapid, and so does the corresponding stiffness reduction.The propagation direction of the main crack tends to be perpendicular to the tensile direction with a higher tensile velocity.The analysis of the strength envelope of the CFRP cross-ply laminate with central hole shows that the tensile strength in the direction with a higher tensile velocity increases gently with the increasing of load ratio.%采用加载臂开槽的中心开孔等厚度十字形试样,实验研究了正交对称铺层碳纤维增强聚合物基复合材料(CFRP)层合板在双轴拉伸载荷作用下的力学行为,分析了3种双轴加载比对其拉伸强度和破坏行为的影响.研究表明:纤维被切断的铺层部分在拉伸作用下容易与其相邻铺层脱粘,导致层合板承载力下降;等双轴加载时,在孔边的被切断纤维与连续纤维间基体在横向拉伸和纵向剪切组合作用下首先开裂;非等双轴加载时,在垂直于快速拉伸方向的铺层中沿孔边应力集中处先出现基体裂纹;随着加载比的增大,快速拉伸方向的细观结构损伤随载荷的增大发展更快,刚度下降更快,破坏时主裂纹的扩展方向更趋于垂直于快速拉伸方向;强度包络线的分析表明快速拉伸方向的拉伸强度随加载比的增大呈缓慢增大的趋势.