Study On The Secondary Functionalization Of Aramid Fiber Surface And Its Composite Milling Process

Aramid fiber is a kind of all-aromatic polyamide special fiber with excellent performance in elastic modulus,tensile strength,wear resistance and chemical stability,the surface of aramid fiber is flat and neat,chemically inert,and the bonding force with the matrix interface is low.Reducing the manufacturing cost and expanding the scale of industrial application are the future directions of aramid fiber development,and its surface functionalization and modification are the key.In this dissertation,dopamine was used to bionically modify the surface of aramid fibers to establish a bridging effect for the deposition of multi-walled carbon nanotubes,which in turn led to the preparation of aramid fiber-reinforced epoxy resin-based composites,giving them electrical properties and improving the mechanical and processing properties of the composites.In this paper,the method and process conditions of dopamine/multi-walled carbon nanotubes modified aramid fibers were investigated,a new general theoretical formula for the mean modulus was proposed,milling tests of the modified composite were performed,and a cutting force prediction model was developed.The main research work and findings of this paper are as follows:(1)The mechanism of the secondary functionalization of the fiber surface was explored,and the method and process conditions of polydopamine/multi-walled carbon nanotubes modified aramid fiber were proposed,and the surface morphology changes of the modified fibers and the surface structure changes were observed to ensure the successful coating of PDA and the smooth deposition of MWCNTs.Electrical properties as well as mechanical and interlayer properties of AFRP were also tested,and a new three-phase modulus calculation formula was proposed based on a shear hysteresis model to investigate the contribution of the two modified materials to the functionalization and performance optimization of AF surfaces.(2)On the basis of the empirical equation of cutting force and cutting mechanics model,considering the pull-out force of some fibers extracted from the resin,the inverse method is used to incorporate the fiber pull-out mechanics model to reflect the holding force of the matrix resin on the reinforcing phase fibers,and the empirical equation of cutting parameters is introduced to obtain the prediction model of cutting force.(3)The machining performance of modified AFRP is analyzed and discussed.The experiments show that the fiber modification can effectively reduce the cutting force generated during the milling process under the same cutting parameters,and the new modified AFRP lay-up process combined with the characteristics of the modified fiber can effectively reduce the machining surface defects and obtain better machining quality.