Research On The Mechanical Properties Of Modified Aramid Weft Jersey Composite Material

In recent years,the frequent occurrence of traffic accidents has resulted in a high number of casualties,so designing more effective safety protection materials has become an urgent need.Weft-knitted composite materials have good formability and energy absorption,and are widely used in the fields of safety protection,transportation and the other fields,in which weft plain knitted composites have better properties.Aramid fiber is widely used as a reinforcement in composite materials due to its ultra high strength and ultra high modulus properties.Therefore,this paper combines aramid fiber with weft plain needle structure to explore composite materials with better performance.Due to the smooth surface of the aramid fiber and the small number of reactive groups,the interfacial adhesion between the fiber and the matrix is poor,which limits its deep development in the field of composite materials.Therefore,two methods are used to modify the aramid fiber and its weft plain knitted fabric to change the chemical properties and surface topography of the fiber,and then improve the interfacial adhesion between the fiber and the substrate.Eight layers of weft-knit composites were prepared by VARTM process to investigate the effect of modification on the mechanical properties of the composites.The first method uses a modified method of LiCl ethanol solution combined with ultrasonic.The effects of the concentration of LiCl ethanol solution on the surface morphology,contact angle,surface functional group,fiber strength and mechanical properties of the weft plain knitted composites were investigated.The results show that with the increase of the concentration of the modified solution,the roughness of the fiber surface increases,the contact angle decreases,and the surface active groups increase.By comparing the mechanical properties of the composites before and after modification,it was found that the mechanical properties of the composites after modification were improved.When the concentration of the composites was 5 wt%,the mechanical properties of the composites reached the best.Compared with the unmodified samples,the tensile,bending and compressive strengths of the composites increased by 43.52%,69.15%and 77.32%,respectively.The second is to modify the aramid fiber and its weft knitted fabric with different concentrations of MWCNTS/CH3C1 solution.The optimum deposition concentration was explored and the effect of the concentration of modified solution on the mechanical properties of the composites was explored.The results showed that when the concentration of modified solution was 0.1 wt%,MWCNTs were most evenly distributed on the fiber surface and no agglomeration occurred.At this time,the mechanical properties of composites are the best.Compared with the unmodified samples,the tensile strength,bending strength and compression strength of composites are increased by 43.48%,52.19%and 65.3%,respectively.Considering the final effect,mass operation and environmental pollution of the two modification methods,the first one is more excellent.Finally,the finite element analysis software ABAQUS is used to simulate the mechanical properties of the composites.By comparing the simulated values with the test results,the failure mode and maximum stress value of the composite material in the simulation process are close to the test results,which paves the way for the further study of the mechanical properties of the composite materials.