Research On The Mechanical Properties Of Modified Aramid Fibers And Their Weft-jersey Composites

With the development of advanced science and technology,high performance fiber has been widely used in the field of composite materials.Among them,aramid fiber,with its excellent properties of high strength and high mold,high temperature resistance,chemical corrosion resistance and so on,stands out in the application of composite reinforcement materials.Because of its unique coil structure,weft knitting structure in textile structure can be used as the reinforcement structure of composite material to give the composite material good energy absorption and impact resistance performance.The combination of the two can give play to their respective advantages to explore better performance of the composite material.However,due to the smooth surface of aramid fiber,rigid macromolecular chain structure and the hindrance effect of aromatic ring,the fiber is chemically inert,so its binding strength with resin is weak,which affects the overall performance of composite materials.Therefore,in this project,surface modification of aramid fiber is carried out to activate the surface of the fiber to improve the interface adhesion between the fiber and the resin matrix,and weft flat knitting composite is prepared to explore the influence of modification methods on the overall mechanical properties of the composite.Firstly,dopamine-doped carbon nanotubes were used to modify aramid fiber and its weft plain fabric,and the effects of carbon nanotubes concentration on the surface morphology,strength,surface groups and properties of composite materials were investigated.The results showed that the dopamine coating with carbon nanotubes on the surface of the fiber was stronger,the ox phenolic hydroxyl group was increased,the strength of the modified aramid fiber was improved,and the shear strength between the modified aramid fiber and the resin matrix was increased.By comparing the mechanical properties of the composite,it was found that the modified mechanical properties were improved.When the carbon nanotube concentration was 0.03%,the maximum tensile strength,bending load and compression stress of the composite increased by 29.96%,16.19% and 17.4%,respectively.On the basis of the first step modification scheme,the second grafting modification was carried out,and the influence of the optimum concentration of silane coupling agent on the mechanical properties of the composite was studied.The results showed that when the silane coupling agent concentration was 2.5%,the maximum tensile strength of the composite increased by 51.6%,the bending load increased by 41.63%,the bending modulus increased by 59.64%,and the compressive stress increased by 32.1%.By comparing the final effects of the two modification methods,the secondary grafting scheme is more excellent when considering the overall properties of the composite.Finally,the finite element analysis software Solidworks and ABAQUS was used to simulate the tensile damage process of single-layer composite materials.By comparing the stress and strain output of the model data with the experimental test results,the error of the two results is within 10%,which confirms the rationality of the model and lays a foundation for the further study of the mechanical properties of composite materials.