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研究了含孔天然苎麻纤维织物/异氰酸酯复合板在双轴向拉伸载荷下的力学行为。对0.5、1.0、2.0、4.0 mm 4种孔径板进行了单向和双轴向载荷拉伸试验,同时采用数字散斑相关方法对全场位移及孔径大小对应变的影响进行了表征。结果表明:当载荷线性变化时孔周围的位移场分布较为均匀;随着载荷接近破坏值,位移场呈非线性分布并出现高应变值点,破坏以极快的速度沿孔边在这些点首先发生。随着孔径的增大,在1000～2000 N双轴向载荷下孔周围相同面积内x、y方向正应变的平均值减小,应变值波动小但范围增大。材料在单向和双轴向拉伸时表现出不同的力学特征:双轴向载荷下失效强度要比单向拉伸时低,降低比例为14%～27%,且随着孔径的增加而增加。
The mechanical behavior of natural ramie fiber / isocyanate composite sheet under biaxial tensile load was studied. Uniaxial and biaxial tensile tests were carried out on four kinds of aperture plates of 0.5, 1.0, 2.0 and 4.0 mm, and the effects of total displacement and aperture size on the strain were characterized by digital speckle correlation method. The results show that when the load changes linearly, the displacement field around the hole is distributed more evenly. As the load approaches the damage value, the displacement field appears nonlinear distribution with high strain point, occur. With the increase of the pore diameter, the average value of positive strain in x and y direction in the same area around the hole decreases with 1000 ~ 2000 N biaxial load, and the strain value fluctuates little but the range increases. The material exhibits different mechanical characteristics in uniaxial and biaxial stretching: the failure strength under biaxial loading is lower than that under uniaxial stretching, with a reduction ratio of 14% -27%, and as the diameter of the bores increases increase.