Theoretical Modeling And Numerical Simulation Of Electrical Conductivity Of Porous Composites

The Composite Conductive Polymeric Materials are widely used in the fields of electric skin,intelligent sensing and human-machine interaction.It is hard for traditional experimental research to predict the conductive properties of the materials and design accurately the structure of materials.Computer simulation technology,based on scientific theory,predicts the shape,structure,performance of materials and provides analysis tools for material design,which has become an important development direction for materials research.The influence factors of the percolation and conductivity has been detected by theoretical modeling and numerical simulation which has an important guiding significance for composite design and theoretical research.In this paper,Monte Carlo method was used to model the percolation of porous composite materials,and a calculation method was proposed.Based on the finite element method,the secondary development of Ansys was performed to calculate the current density of composite materials.The main tasks are as follows:(1)A three-dimensional porous single-filler model was constructed,and the percolation threshold and current density of the model were detected with the filler,the pore size and porosity.The results show that the percolation threshold of porous model is much smaller than non-porous single filler model.In porous model,the larger aspect ratio of the filler model has a smaller percolation threshold;when the volume fraction of the filler is unchanged,the model whose aspect ratio is larger has a larger current density.The larger pore radius leads to the smaller current density of the model.(2)A three-dimensional porous mixed model was constructed to study the influence factors of the percolation threshold and current density.The results show that the porous mixed model has a smaller percolation threshold than the porous singlefiller and non-porous mixed-filler models.And the current density of the porous mixed model is greater when the filler content is the same;With the increase of the radius of sphere filler,the current density firstly increases and then decreases.And when the radius of the spherical filler is about 2 times of the stick fillers,the current density of the system is the largest.(3)The barriers characteristics of tunneling effect at different stages were studied,and a piecewise model for resistance calculation was proposed based on the tunneling effect and piezoresistive characteristics.Meanwhile,reliability of this model was verified by the experimental and simulation studies of PI / CNTs porous conductive piezoresistive materials.The research results show the relative error is only 6.5% when the deformation is less than 20%,which demonstrates that the piecewise model has a better description of the piezoresistive properties of porous composites than traditional models.