Study On The Surface Modification Of Aramid Fiber And Mechanical Properties Of Its Weft Knitted Stitched Composite

Aramid fiber has high modulus,high strength,and its composite material has good mechanical properties,which is widely used in military protection,aerospace and industrial construction.Weft flat knitting composite material has strong energy absorption and is easy to be formed for complex structures.It is widely used in safety protection,automobile industry and other fields.Due to the lack of polar functional groups in the macromolecular chain of aramid fiber and the smooth surface,the adhesion between the fiber and the resin matrix is poor,which affects the mechanical properties of the composites.To solve this problem,the surface modification of aramid fiber and its weft plain knitted fabric was carried out in this paper to increase the surface activity and roughness of aramid fiber and to improve its adhesion with resin matrix.Design a new type of chain stitch stitch8-layer plain knitted fabric and prepare the weft plain knitted composite by VARTM process.The mechanical properties of the composite were investigated before and after modification.Aramid fiber and its plain knitted fabric were modified by dopamine-PEAGO.The results showed that the strength of the aramid fibers increased by 17.9% and31%,and the interfacial shear strength of the aramid fibers increased by 45.25% and45%,respectively,compared with that without modification.Comparing with the mechanical properties of the unmodified composite,it was found that the mechanical properties of the modified suture composite were improved.When the concentration of dopamine was 0.5%,the mechanical properties were significantly improved.The tensile modulus,bending load,compression and impact stress of the composites were increased by 48.24%,74.02%,93.87% and 72.55%,respectively,compared with those of the unmodified and unstitched composites,which were increased by 40.21%,54.73%,85.31% and 43.28%.Aramid fiber and its weft plain knitted fabric were grafted by argon plasma with different GLYMO solution.The results showed that when the mass fraction of GLYMO solution was 1.5wt%,the tensile load and interfacial shear strength of aramid fibers were the highest,and the fibers before and after grafting increased by 42.95%,47.52%and 24.49%,27.71% compared with the original fibers,respectively.It is found that the mechanical properties of the modified suture composite are improved,among which1.5wt% is the most improved.Compared with the unmodified suture composite,its maximum tensile load,bending load,compressive strength and impact stress are increased by 79.60%,41.38%,31.13% and 46.61%,respectively.Compared with the unmodified sutured sample,the increase was 65.87%,25.70%,25.34% and 21.73%,respectively.Comparing the final result,operation process and mass production of the two modification methods,the first modification method is better.Finally,a three-layer knitted suture model was created using RHINOCEROS software,and the compression properties of single-cell suture composites were simulated using ABAQUS.By comparing the simulated data with the experimental results,it is found that the error between the two results is within 10%,which confirms the rationality of the model and lays a foundation for further simulation calculation of the mechanical properties of the suture composites.