The Effects Of SiC Nanowires On The Dynamic Mechanical Properties Of STF And The Pull-out Force Of Fabric Impregnated With STF

Shear thickening fluid（STF）is a kind of dense suspensions which consists of nano-particles and dispersing medium,and its apparent viscosity can increases dramatically,even into solid-like state when subjected to impact loading,and it will recover as soon as the load is removed.Due to its highly nonlinear mechanical properties,STF is promising in the application of damping and noise reducing,safety protection etc.Therefore,the design and preparation of the high performance STFs have become an important research topic.The reinforced STF was made from SiC nanowires and SiO₂ nanoparticle-based STF.The rheological properties of SiC nanowires reinforced STF were measured by a rheometer to explore the effects of SiC nanowires on the rheological properties,combining with the hydrodynamic cluster theory,the effect of the mechanism of SiC nanowires on the viscosity of STF was discussed.Then the dynamic response of reinforced STF was investigated by a Split-Hopkinson pressure bar（SHPB）at high strain rates to study the effects of SiC nanowires on the dynamic response of STF.The strengthen mechanism of SiC nanowires on the dynamic properties of STF were discussed.The single yarn pull-out behaviors of Kevlar fabric impregnated with STFs were investigated.An analytical model of yarn pull-out was used to simulate the response of each test,the strengthen mechanism of STFs was discussed by the shear parameters obtained from simulation.The results are as follows:（1）The results of rheological experiments showed that compared to the rheological properties of SiO₂ nanoparticles-based STF,the initial and shear thickening viscosity of the reinforced STF were higher than nanoparticles-based STF,moreover the promotion was more significant as the amount of SiC nanowires increased.The SiC nanowires in STF at a quasi-static or at a less than critical shear rate,were distributed between the nanoparticles,which hindered the flow of particles,so the initial viscosity of reinforced STF was higher.When the shear rate reached the critical value,the particle clusters formed in STF were prevented from slipping and collapsing by SiC nanowires.So the viscosity of reinforced STF in thickening period increased.（2）The results of the dynamic experiments showed that with the strain rates increasing,the increasing trend of the flow stress of SiO₂ nanoparticles-based STF decreased,and reached a saturation value.Whereas the flow stress of the reinforced STF increased with increasing strain rates and there was not a stauration.The SiC nanowires increased the lubrication force between particles at high strain rate.It means that the reinforced STF have a more excellent dynamic load capacity.（3）The results of single yarn pull-out showed that the STFs have a significant influence on the yarn pull-out force.The yarn pull-out forces of Kevlar fabric impregnated with STFs increased with increasing the pull-out speed.Compared the results of Kevlar impregnated with SiO₂ nanoparticles-based STF,SiC nanowires reinforced STF had a more significant effect on the performance of yarn pull-out of fabric.The simulation results showed that the STFs have improved not only the bond strength but also the friction between yarns,so the yarn pull-out performance of fabric can be improved.