Numerical Simulation Of The Mechanical-electric Response Sensitivity Of Conductive Polymer Composites Filled With Carbon Nanotubes

Conductive polymer composites filled with carbon nanotube have broad application prospects in the field of flexible sensors due to their unique electrical and mechanical properties.However,sensors manufactured by this kind of material always have single-function and poor designability at present.Due to the limitation of objective conditions in experimental research,it is difficult to accurately control the microstructure of the filler inside,while these microstructures can be accurately reproduced by the numerical simulation technology.Therefore,numerical simulation has unique advantages in studying the properties of such materials.However,current commercial software cannot directly simulate the mechanical-electric response of conductive composites.The finite element simulation scheme using "beam element + solid element" reported in the literature has problems such as local stiffness increases and mismatching of degrees of the freedom.In this paper,a real three-dimensional scheme is designed,based on the tunnel resistance theory,to simulate the mechanical-electric response of conductive polymer composites at the mesoscopic scale.Then,the correctness of the simulation scheme is verified through experiments.At the same time,the main factors affecting the variation of "tunnel resistance between conductive fillers " and "conductive network or topology structure" during the deformation process were explored by a set of numerical simulation combined with orthogonal experiment.The main work of this article is as follows:(1)The theoretical model and numerical method of mechanical-electric coupling simulation are briefly introduced.Based on Monte Carlo method,some threedimensional representative volume elements(RVEs)of conductive polymer composites filled with carbon nanotubes are established with Digimat and UG software.(2)Based on the tunnel resistance theory,a real three-dimensional scheme is proposed to simulate the mechanical-electric response of conductive polymer composites.In this scheme,the APDL function of ANSYS and a set of in-house software written with C ++ language are firstly used to search the tunnel element and conductive path in RVE.Then these results are imported into ANSYS to calculate the deformation and potential of polymer matrix and conductive fillers under different conditions using real three-dimensional solid elements.(3)Some mechanical-electric response experiments of MWCNTs / TPU were carried out to verify the correctness of the simulation scheme in this paper.When different matrix modulus of the polymer are concerned,both experimental and simulation results show the same tendency that the mechanical-electric response sensitivity of RVE is increased along with the modulus ratio of filler to matrix.This proves that the numerical simulation scheme in this paper is reasonable.(4)Six factors influencing the mechanical-electric response sensitivity induced by the variation of tunnel resistance were analyzed by orthogonal simulation experiments.The results show that the modulus ratio of filler to matrix,the aspect ratio of CNTs and the CNT's orientation are the first three factors.Also,four factors influencing the sensitivity induced by the variation of conducting network were explored.The results show that the modulus ratio of filler to matrix and the orientation of CNTs are important.The real three-dimensional mechanical-electric simulation scheme operated in this paper provides an effective method for the design of the sensitivity of CPC's sensors filled with conductive fillers.And it provides the support and reference for the quantitative design of sensors.