双轴载荷下复合材料十字型试样几何形状对中心测试区系数的影响

基于双轴拉伸载荷下复合材料十字型试样的设计特点,对比分析了不同几何形状的十字型试样在不同厚度比和载荷比条件下中心测试区应力集中系数和承力系数的变化规律,并开展了不同载荷比的双轴拉伸实验进行验证。研究表明:十字型试样中心测试区系数与载荷大小无关,与试样几何形状、厚度比及载荷比有关;等宽加载臂宽度越小、厚度比越大,应力集中系数越小,载荷比不同,应力集中系数也不同;一般而言,中心测试区承力系数随厚度比增加而增大,x向承力系数βx随载荷比增加呈非线性增大,y向承力系数βy随载荷比增加呈线性减小;在双轴拉伸载荷条件下,形状D十字型试样在载荷比f=4/1时中心测试区y向应力分量为负值,表现为压应力状态。

Influence of geometry of composite cruciform specimen under biaxial loading on coefficients of central testing zone

Based on the features of composite cruciform specimens under biaxial tensile loading, we analyzed the rules of how stress concentration factors and loading coefficients of the central testing zone in the cruciform specimens of different geometric shapes, change with different thickness ratios and load ratio conditions. The biaxial tensile tests with different load ratios were implemented for verification. The results show that the coefficients of the central testing zone have nothing to do with the loading magnitude, but are related to geometric shapes, thickness ratios and loading ratios. Smaller width of equal-width loading arms and larger thickness ratio contribute to smaller stress concentration factors, and different load ratios mean different stress concentration factors. Generally, the loading coefficients increase along with the increase of thickness ratios. The x-axis loading coefficient β_x rises nonlinearly while the y-axis coefficient β_y decreases linearly with the increase of load ratios. In addition, for the D-shaped cruciform specimen under biaxial tensile loading, the y-axis stress component of the central testing zone is negative when the load ratio f=4/1, and the central area shows a state of compressive stress.