无纺织物单向拉伸孔径变化试验与理论预测对比分析

无纺织物作为反滤材料,常处于单向受拉工作状态。单向拉伸引起无纺织物孔径变化,易导致反滤工程失效。通过控制织物应变的干筛试验,定量测试了无侧限单向拉应变逐级增大的过程中,两种不同厚度短纤针刺无纺织物的孔径分布曲线变化。采用干筛试验结果,对现有两种体系的单向应变下无纺织物孔径预测理论解进行验证:一类是佘巍等效孔径O95理论解,一类是Rawal孔径分布曲线理论解。通过对比两种理论解对各级拉应变下的O95值预测,归纳二者的预测误差规律,从理论假设出发分析误差原因。同时采用前人图像法测得的热粘无纺织物O95变化验证两类理论解。两种理论解均能较好地预测无侧限单向拉应变下无纺织物O95的变化规律。O95随单向拉应变呈近似线性减小的规律。对于O95变化斜率的预测,佘巍解较准确,Rawal解偏大。对于O95数值预测可结合两类理论解给出变化范围。

Analytical prediction and experimental research on pore size of nonwoven geotextiles under unconfined uniaxial tensile strain

The filtration applications of nonwoven geotextiles are usually subjected to uniaxial tensile strain, resulting in the variation of pore sizes and failure of filtration engineering. The pore-size distributions of two needle-punched nonwoven geotextiles subjected to unconfined uniaxial tensile strains are measured by using the strain-controlled dry sieving tests. The experimental results of the dry sieving tests are compared with the predictions of two analytical solutions. One is the analytical solution of equivalent opening size O₉₅ proposed by She Wei. The other is the analytical solution of pore-size distribution proposed by Rawal et al. The experimental values of O₉₅ of two thermally bonded nonwoven geotextiles tested by previous studies are used to confirm the validity of the two analytical solutions. By comparing the predictions of O₉₅, the accuracy and the error of two analytical solutions are analyzed. O₉₅ decreases approximately linearly with unconfined uniaxial tensile strains. The prediction of the variation rate by She Wei is accurate, while that by Rawal et al. is larger than the experimental rate. The prediction of the value of O₉₅ should be done considering the results of She Wei solution and Rawal solution.