Preparation and stab-resistance of composites fabricated by aramid fabric impregnated with SiO2/poly(ethylene glycol)200/multi-walled carbon nanotube shear thickening solution
Objective In recent years,flexible stab-resistant materials have gradually replaced traditional hard stab-resistant materials,and high-performance fabrics become an important research object for flexible stab-resistant materials.In order to optimize the stab resistance of high-performance fabrics,reduce the number of stacked layers and the quality,it is necessary to prepare composites with both flexibility and stab resistance properties.Method In this study,multi-phase shear thickening fluids(MSTFs)were prepared by polyethylene glycol 200,SiO2 and multi-walled carbon nanotubes(MWCNTs),and the effects of the aspect ratio and addition amount of MWCNTs on rheological properties of STF were studied.A MSTFs composite fabric was prepared by dipping and drying,and a composite fabric was fabricated by coated silicon carbide/thermoplastic polyure-thanes(SiC/TPU)on the aramid fabric.Yarn pull-out test and quasi-static stab test were conducted to evaluate the stab resistance of the composite fabrics.In addition,double layer composite fabrics with the two different composite fabrics were prepared to investigate the effect of the stacking sequence on the stab resistance.Results The study shows that the carbon nanotubes with larger aspect ratio were better in improving the thickening effect of STF,the maximal viscosity of MSTFs(0.4％MWCNTs-A)increased by 52 Pa·s over MSTFs(0.4％MWCNTs-B).and with the increase of the content of MWCNTs,the critical shear rate of the MSTFs became smaller,and the maximum viscosity value was gradually increased.In addition,from the results of yarn pulling-out test and the quasi-static stab resistance test,the performance of composite fabrics were seen to be improved greatly compared to neat fabrics.The MSTFs composite fabrics have more interyarn friction than the pure 68％STF composite fabric,and with the increase of the MWCNTs addition in the MSTFs,the maximum pull-out load between the yarns of the composite fabric increases first and then decreases,and the friction between yarns of MSTFs composite fabric is related to the yarn pull-out speed.the study found a pronounced effect of the MSTFs on the ability of stab resistance was noticed,the maximum puncture load of MSTFs composite fabrics was greater than that of the pure 68％STF composite fabric under unit areal density,and the maximum puncture load demonstrated a gradual increase as the content of MWCNTs increased in MSTFs.However,When the content of MWCNTs is 0.6％,the initial viscosity of MSTF was larger,the weight-growth rate of the composite fabric was increased,and most of the liquid remained on the surface of the fabric,affecting the performance of the composite fabric.According to the experiments,the penetration velocity of tested long nails was 25 mm/min,the maximum puncture load of MSTFs(0.4％MWCNTs-A)-impregnated aramid fabric was 154.33％higher than that of pure 68％STF-impregnated aramid fabric.In the experiments to explore the influence of the laminated structure of different composite materials on the anti-stab performance,the study found that,the double-layer fabrics which the shear thickening liquid impregnated fabric as the surface layer and the SiC/TPU coated fabric as the back layer(S/T)has the biggest maximum puncture load,which is 786.26％higher than that of the double-layer pure fabric.Conclusion The study shows that the addition of MWCNTs improve the rheological properties of MSTFs,and the fabrics impregnated with MSTFs optimize the stab resistance performance of neat aramid fabrics effectively.When the fabric is impacted,the viscosity of MSTFs increases quickly,and composite fabric has a tighter bond between the fibers,further improving the puncture resistance of composite fabrics.Moreover,experiments show that since the stab-proof mechanism of MSTFs composite fabric and SiC/TPU coated fabric is not exactly the same,the laminated composites of shear thickening liquid impregnated fabric as the surface layer and SiC/TPU coated fabric as the back layer demonstrates excellent puncture resistance performance,offering ideas for design of the laminated structure of the multi-layer stab-resistant material.
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