Research On Mechanical-Electrical Properties Of Conductive Polymer Based On Finite Element Simulation

In this paper,COMSOL finite element software is used to establish a two-dimensional finite element model of the mechanical,electrical and mechanical-electric coupling of composite materials.By using the simulation model,the stress relaxation and stress-strain relationship of the composite material are analyzed,and the post-processing cloud image is established to analyze the changes of the mechanical and electrical properties of the composite material.At the same time,the effect of carbon black(CB)particle content on the elastic modulus,hardness,creep and stress relaxation of CB/PP(polypropylene)composite materials was experimentally studied.Change of macro properties of materials are simulated from a microscopic perspective by simulation analysis and experimental methods.Firstly,mechanical properties of CB/PP composites were measured by nano indenter.The changes of elastic modulus and hardness of composite materials with different CB contents are tested.The experimental results show that CB will significantly increase elastic modulus of the composite.While hardness increases slowly with the the increasing CB content,then increases rapidly,and in the end tends to be horizontal or slightly decreased.Creep stress index and creep characteristic relaxation time of the composite material are solved based on experimental data.The results show that the creep stress index increases,whilethe creep characteristic relaxation time decreases with the increase of CB content.Secondly,COMSOL software and finite element method are introduced.According to the viscoelastic properties of the composite,the generalized Maxwell model was used to characterize the mechanical properties of CB/PP composite.SEM experimental results show that the fillers are uniformly distributed in matrix.Distance between particles decreases with the filler content.Based on size and distribution of carbon black particles observed on SEM,two-dimensional geometric models of single cells and multiple cells were established.The stress relaxation properties of composite materials with different CB contents were tested by using a universal testing machine(MTS).According to experimental results,the stress relaxation model of CB/PP composites is established,and the stress relaxation curve is obtained.The comparison between experiment and finite element simulation proves the rationality of the simulation model.According to the principle of time-temperature conversion,the effect of temperature on the stress relaxation of PP materials is simulated.A stress-strain model of PP material was established,and a two-dimensional model of a unit cell of composite material with different CB contents and different strain conditions was established based on the stress-strain model.Stress distribution around the particles in the composite material is analyzed,and the slip and interface debonding between PP and CB are predicted.Finally,two-dimensional models of regular distribution and random distribution of particles are established,the difference between the two models is compared and the interaction between particles is analyzed.Finally,a multi-physics coupled finite element model of electrostatic-solid mechanics is established.It is found that as the carbon black content increases,the resistivity of the composite decreases.According to the change of current density,the percolation threshold of the composite material is predicted to be 8%-12%,which is consistent with the experimental results.Through the study of the internal potential,field strength distribution and polarization phenomena in the composite material,it is found that the addition of CB reduces the spacing between particles,which will be beneficial to the formation of tunnel current between particles.Electrical conductivity of the composite will increases with the content of CB.According to the analysis of the electric field cloud diagram and the solution of the boundary electric field strength,it is found that when the strain increase,internal field strength and current between particles will increases,while spaces between particles decreases.