| With the development of technology, people’s protection awareness iscontinuously strengthening and the requirements for bulletproof materials areimproved, which draws more and more public attention to come up with a bodyamour with good bulletproof property and comfort. Scholars at home and abroadhave made much contribution to studying bulletproof materials while the researcheson shear thickening liquid applied in bulletproof material are relatively few. So it isquite necessary to explore the composite materials made of shear thickening liquidand bulletproof materials which will be valuable.In this thesis, shear thickening liquid is prepared and the ballistic performance ofits composite materials is studied.The main raw material is tested and analyzed usingpycnometer, TEM, FTIR and XRD and the preparation technology of STF and itsrheological properties are mainly explored. The preparation process of STF-flexiblecomposites and its basic properties are discussed. Meanwhile countless water ethanolremoval process, layer upon layer connection technology and bullet-proofperformance are explored. The factors which influence bulletproof performance,ofSTF-flexible composited materials are studied and the bulletproof mechanism areanalyzed. The following conclusions can be drawn.(1) The SiO2particles with the approximate circle have good monodispersity,made up of amorphous material. The upper limits of the amount of SiO2with particlesize20nm,35nm and50nm in corresponding STF are respectively78.81%,79.10%and79.40%. STF map shows that there is no reaction in STF dispersions and whenSiO2content in the solid dispersions exceeds30%, the shear thickening behavior willhappen in STF system;with the increase of solid content of SiO2, the initial andmaximum viscosity of STF system both increase and increasing efficiency goes upwhile the STF system critical shear rate is decreasing.;with the increase of particlesize, the initial viscosity of STF system and maximum viscosity is reducing while STF system critical shear rate is decreasing; with the increase of molecular weight ofPEG, the STF system initial viscosity increases while the critical shear rate decreases.(2) Under the condition of this experiment, the viscosity of different SiO2composite solids system decreased but the basic system of STF starting compoundviscosity increased realtively with the increase of the angular frequency. The systemof which the SiO2particle diameter is50nm can witness phenomenon of shearthickening but neither does it when it comes to20nm and35nm. So the STF systemcomposite viscosity reduces with the increase of particle size. No shear thickeningphenomenon occurs in the system whose STF is of different molecular weights.With the increase of PEG molecular weight, the system’ initial viscosity of compositewere7.98Pa.s,11.9Pa. s and14Pa.s.(3)By reversible research, it can be found that the curve lines of shear rate from0.1s-1to2000s-1and from2000s-1to0.1s-1basically coincide. And they all have shearthickening effect which shows the STF system has good reversibility; Steady-staterheological properties research was conducted on the different molecular weight ofPEG, and the results show that PEG has no shear thickening effect.(4) The strength of experimental aramid filament is134.00N and the fracturestrength of it is116.4cN/Tex. With the increasing of solid content of SiO2, the warpand weft’ maximum tensile stress and tensile strain of pure aramid fabrics withdifferent SiO2solids STF-flexible composite are stable. With the increasing of solidcontent of SiO2, the weight increasing of STF-flexible composites is greater while thefabric air permeability decreases, When the samples shares the same proportion ofSiO2, the air permeability of homemade plain weave fabric is lower than that of thebought Kevlar fabric. Among all those fabrics, the air permeability of threedimensional fabric is the lowest. And with the increasing of layer number, the airpermeability decreases. With the increasing of the number of polypropylene picks, theinterweave resistance of fabric also increases. With the increasing of linear density ofpolypropylene fiber, the interweave resistance of fabric increases but the degree ofincreasing reduces.(5)The absorbed energy of STF-flexible composite material in unit area is more than that of pure Kevlar fabric. With the layer number increasing, the bulletproofperformance is getting better and better and some of the samples which contain morelayers can’t be shot through by the gunshot. The order of layer angle arranged byenergy absorbance in the same or similar surface density in unit area from high to lowis45°>90°>0°.The three dimensional fabric has a better bulletproof performancethan plain weave fabric. With the increasing of the three dimensional fabric layernumber, the fabric can absorb more energy. From the SEM photos, it can be seen thatKevlar fibers deformed, fractured and pulled out when absorbing energy. Thebulletproof performance of STF-flexible composites without TPU connectionimproves in a row when the speration distance between TPU layers is from16cm to8cm. When the sepration distance is certain, the width of resin in STF-flexiblecomposite can be arranged according to the ability of improving bulletproofperformance from bad to good:0.5cm<1cm<1.5cm<2cm. But the STF-flexiblecomposite material does not change significantly on the overall energy absorption.The bulletproof performance can be much better with the increasing of PEGmolecular weight and SiO2grain size. The bulletproof performance of STF-flexiblecomposite material can be improved by increasing the linear density of polypropylenepicks and adding in more polypropylene picks.(6) The main ways of STF-flexible composite materials absorbing the bulletkinetic energy are pumping, deformation and fracture of Kevlar fibers, high stresswave propagation speed in a Kevlar fabric and the energy dissipation,TPU resinfracture and STF-flexible composite material layering and STF system viscosityincreasing and blocking the invasion of the bullet. |
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