中文摘要：

为探究Kevlar 49单束的尺寸效应及应变率敏感性,首先,利用MTS万能试验机对不同标距（25、50、100、150、200和300mm）的Kevlar 49单束进行了准静态（应变率为1/600s^-1）拉伸测试;然后,利用Instron落锤冲击系统对标距为25mm的试样进行了动态（应变率为40-160s^-1）拉伸测试;最后,利用Weibull模型进行统计分析,量化了不同标距和应变率下Kevlar 49单束拉伸强度的随机变化程度。结果表明：Kevlar 49单束的拉伸力学性能与标距和应变率有相关性;拉伸强度随标距的增加而减小,但随应变率的增加而增大;峰值应变和韧性均随标距和应变率的增加而减小;提取的Weibull参数可用于数值模拟及工程应用。

英文摘要：

In order to investigate the size effects and strain rate sensitivity of Kevlar 49 single yarn,quasi-static（strain rate is 1/600s^-1）tensile tests were conducted on Kevlar 49 single yarns with different gauge lengths（25,50,100,150,200 and 300 mm）using MTS universal testing machine firstly.Then,dynamic（strain rate is 40-60s^-1）tensile tests were also conducted on samples whose gauge length is 25 mm by Instron drop-weight impact system.Finally,Weibull model was used in statistics analysis,and the degree of random variability in tensile strength of Kevlar 49 single yarns under different gauge lengths and strain rates was quantified.The results show that the tensile mechanical properties of Kevlar 49 single yarns have correlation with gauge length and strain rate.Tensile strength decreases with increasing gauge length,but increases with increasing strain rate.While ultimate strain and toughness both decrease with increasing gauge length and strain rate.The extract Weibull parameters can be used in numerical simulation and engineering application.