黄麻纤维束力学性能的尺寸和应变率效应

为了探究黄麻纤维束的尺寸效应和应变率敏感性,利用C43电子式万能试验机和CEAST 9340落锤试验冲击系统分别在静动载条件下对黄麻纤维束进行测试,获得了杨氏模量、强度、峰值应变和韧性随标距和应变率的变化关系静载试验在1/600s-1应变率条件下进行,测试了6组不同标距(25、50、100、150、200和300mm)的试件;动载试验以应变率为变量,在4组不同的应变率(40、80、120和160s-1)条件下进行了测试,试件标距均为25mm。测试结果表明:随着试件标距增大,杨氏模量初始增大,当标距大于100mm时趋于稳定;强度、峰值应变和韧性均减小。随着应变率增大,杨氏模量和强度均增大;峰值应变初始减小后趋于稳定;韧性先减小后增大。鉴于植物纤维束材料较大的性能离散性,采用Weibull分布对试验数据进行拟合,获得了黄麻纤维束强度在不同试验条件(标距和应变率)下的分布规律。

Effects of gauge length and strain rate on tensile behavior of j ute yarns

In order to investigate the size effect and the sensibility of strain rate of the j ute yarns,the quasi-static tests were conducted by utilizing a C43 electromechanical universal test system and dynamic tests were performed by utilizing a CEAST 9340 drop-weight impact system.The correlations between mechanical parameters (Young’s modulus,tensile strength,ultimate strain and toughness)and experimental conditions (gauge lengths and strain rates)were obtained through the tests.The samples with six different gauge lengths (25,50,100,150,200 and 300 mm)were tested at the strain rate of 1/600 s-1 in the quasi-static tests,and the samples with the gauge length of 25 mm were tested over four different strain rates (40,80,120 and 160 s-1 )in the dynamic tests in which the strain rate was a variable.The experimental results show that Young’s modulus increases initially,and then tends to be stable when the gauge length is larger than 100 mm,while tensile strength,ultimate strain and toughness de-crease with increasing the gauge length.As the strain rate increases,Young’s modulus and tensile strength increase,while ultimate strain decreases initially and then maintains constant,and toughness decreases initially but then increases.Due to the large scatter in the material properties of plant yarns,Weibull distribution was used to fit the experimental data,by which the distribution of tensile strength of the j ute yarns under different experimental conditions (gauge length and strain rate)were obtained.