Kevlar29纱线动态拉伸力学性能与本构方程OACSTPCD

In order to clearly characterize the mechanical behavior of Kevlar29 yarn at different strain rates,this paper reports quasi-static and dynamic tensile tests on Kevlar29 yarn.Combined with the split Hopkinson tensile bar(SHTB)theory and motion target tracking method,the stress-strain curves of Kevlar29 yam at different strain rates are accurately obtained,and then the deformation and fracture process of yam dynamic tension are analyzed,revealing the strain rate effect of Kevlar29 yam mechanical properties.Based on the strain rate effect of yarn,a viscoelastic constitutive equation is obtained through the least squares fitting method,and the differences and applicability between the three-element and five-element constitutive models are analyzed.The results show that when the strain is calculated by identifying the coordinates of the marker points on the yam by the motion target tracking method,it is more accurate than the strain calculated directly from the waveform measured by SHTB.The quasi-static mechanical properties and dynamic mechanical properties of Kevlar29 yarn differ significantly,e.g.,the dynamic tensile modulus and tensile strength are higher than those of quasi-static,and the dynamic fracture strain is smaller than that of quasi-static.In the strain rate range of 0.001-700 s-1,with the increase of strain rate,the breaking strain of Kevlar29 yarn decreases,and the tensile strength,tensile modulus and toughness all increase first,but at higher strain rates,the tensile strength(higher than 497.5 s1)and toughness(higher than 330.7 s-1)decrease,while the tensile modulus(higher than 330.7 s-1)tends to be stable.The viscoelastic constitutive equation can better characterize the strain rate effect of the mechanical properties of Kevlar29 yarn,but the viscoelastic constitutive model cannot reflect the nonlinear stress-strain relationship of the yarn before fracture.Relatively speaking,the fitting effect of the five-element viscoelastic model is better than that of the three-element viscoelastic model.