Performance Optimization Of Shear Thickening Liquid And Research On Stab Resistance And Mechanism Of Kevlar Composite Fabric

With the frequent occurrence of regional conflicts and riots around the world,in many countries,the restrictions on gun ownership have led to increasing sharp weapons attacks.However,the traditional stab-resistant materials require multiple layers to ensure the protection level,which are inflexible,heavy,high cost and restricting the agility of the wearer.Although the researches on stab-resistant materials have solved some problems,there is still a lack of sufficient theoretical guidance.In response to the current problem,this paper first established numerical models of quasi-static and dynamic stab-resistant process of Kevlar woven fabric.Based on the results of stabresistant mechanism,the intelligent response material shear thickening fluid(STF)was introduced and the STF/Kevlar fabrics were also fabricated.The rheological property of STF was taken as the breakthrough point and the stab-resistant performance of STF/Kevlar fabric was taken as the main line.According to both the experimental research and finite element model analysis,the results of failure mode and energy absorption distribution could be obtained.Based on these results,the internal relationship between the shear thickening mechanism of STF and the improvement of STF/Kevlar fabrics stab-resistance could be investaged.The main research contents are as follow,The thesis firstly established the quasi-static and dynamic stab-resistance models related to the fabric and knife structure parameters,based on the characteristic curve of the Kevlar fabric stab-resistant process,Newton’s law,energy and momentum conservation.The models were calculated through MATLAB software,so the “forcedisplacement” and “force-time” curves of the fabric stab resistance process were obtained.The whole process of the fabric stab-resistance performance could be predicted through these models and the main factors were also summarized.On the basis of the above researches,STF was introduced to improve the stab-resistance of fabrics.The rheological property of STF was controlled by some factors such as mass fraction of dispersed phase,particle size,chemical structure of the dispersion medium and temperature.In order to further improved the rheological property,the oxygen plasma treated carbon nanotubes(MWNT)were added to the STF system.Based on the “hydrocluster” theory and the force analysis of the dispersed phase particles,the enhancement mechanism of MWNT to STF system was also explored.And then the effect of adsorption capacity on the quasi-static stab-resistance and weight gain rate of the STF/Kevlar fabrics were explored using Response Surface Methodology.Combined with the results of quasi-static and dynamic stab resistance tests,friction between yarns,fabric failure diagrams,the mechanism of shear thickening effect on the fabric stabresistance improvement was qualitatively analyzed.Finally,a mesoscopic model of MWNT/STF/Kevlar fabric(MSK)was established with the ABAQUS software,combined with the user subroutine VUSDFLD to define the material property of MWNT/STF with FORTRAN language.The model reproduced the local failure deformation and stress distribution nephograph of the MSK fabric at various stages during the quasi-static and dynamic stab processes.Based on the MSK fabric energy absorption distributionin terms of viscosity,friction,strain energy and kinetic energy,it fully revealed the mechanism of MWNT/STF and the interaction between MWNT/STF and fabric under different knife speeds.