Research On Dynamic Mechanical Behavior And Numerical Simulation Method Of STF-Kevlar Fabrics

High-strength Kevlar fiber woven fabrics are widely used in the aero-engine soft-wall machine casing.The shear thickening fluid was found to be effective in enhancing the energy absorption capacity of Kevlar fabrics.Therefore,the application of STF reinforced Kevlar fabrics to the machine casing could increase containment and reduce system weight,it has a broad vision of application.Containment process involved the impact of large deformation process and the key process of finite element analysis of the impact was accurate material constitutive model.In order to obtain a constitutive model parameter suitable for pure Kevlar and STF-Kevlar fabrics at high strain rates,the following work was done:(1)Designed the corresponding stiffener and fixture for single bundle fiber,tests were carried out on the MTS material testing machine and Hopkinson bar at room temperature(20℃)to obtain the quasi-static and dynamic tensile mechanical properties of single Kevlar fibers and Kevlar reinforced with different concentrations of STF.The differences between quasi-static and dynamic mechanical properties and the strengthen effects of different concentrations of STF on the elastic modulus,stress limit and tensile strength were analyzed comparatively,provided a reference for the dynamic response analysis of STF reinforced Kevlar fabric.(2)The fiber pull-out tests at two pull-out rate were carried out on pure Kevlar and STF-Kevlar fabrics and the coefficient of friction between the yarns was obtained.It was found that the coefficient of friction of the STF-Kevlar fabrics was significantly higher than that of pure Kevlar fabrics.With the pull-out rate increased,the friction coefficient of pure Kevlar decreases,while the friction coefficient of STF-Kevlar increased.(3)Based on the Microstructure of yarns required by the Numerical Microscope,established mesoscopic geometric model,then with UG、HyperMesh and ANSYS / LS-DYNA finite element analysis software,established the yarn-level finite-element model of Kevlar fabric.The constitutive relation of yarn was defined by the key words of orthotropic material model,The yarn failure was described by the theory of maximum tensile stress failure.The model material parameter was verified by simulating the stretching process of single yarn,established the numerical analysis method of high speed impact of STF-Kevlar fabric.(4)The impact tests of imitation blade onto Kevlar fabrics were carried out at the air gun system,the results showed there is good consistency between the impact process and energy absorption of pure Kevlar simulation and test.The influence of friction coefficient and failure stress on the energy absorption of STF-Kevlar fabric was investigated.It was found that the shear thickening fluid significantly enhanced the energy absorption of Kevlar fabric.The failure stress significantly affected the absorption capacity of fabric,the greater the failure stress,the more energy absorbed.The friction coefficient indirectly affects the energy absorption capacity of the fabric by affecting the amount of yarn involved,the higher the friction coefficient,the less the absorption energy.The research in this paper provided a theoretical basis and an analytical method for the application of STF-Kevlar fabric in aeroengine soft-wall tolerant casing.