Numerical Simulation And Experimental Study On Piezoresistive Effect Of Carbon Nanotube Cement-based Composites With Pore Water

Carbon nanotubes(CNTs)have good electrical and mechanical properties,which can be incorporated into the composites as an external phase to improve the mechanical and electrical properties of the composites.In this thesis,based on the pressure sensitive characteristics of carbon nanotube composites,a numerical simulation and experimental study on the piezoresistive effect of carbon nanotube cement-based composites with pore water was carried out.In this thesis,the non-uniform distribution of pore water and carbon nanotubes in cement-based composites and the agglomeration of carbon nanotubes in cement-based composites are considered.Due to the lack of authenticity in the current conventional simulation,a three-dimensional random field of pore water and carbon nanotubes was established to simulate the random distribution of pore water and carbon nanotubes in cement-based materials.Combined with Mori Tanaka method,the electrical properties of carbon nanotube cement-based composites with pore water were studied,and the effective conductivity prediction theory was deduced.Then three models of effective conductivity prediction of carbon nanotube cement-based composites with pore water were proposed:(1)effective conductivity prediction of pore water cement-based two-phase model;(2)effective conductivity prediction of carbon nanotube cement-based two-phase model;(3)effective conductivity prediction of pore water carbon nanotubes cement-based three-phase model.According to the characteristics of pressure sensitivity of carbon nanotube cement-based composites with pore water,the theory of piezoresistive effect of the cement-based composites was deduced.On this basis,the isoparametric finite element analysis method was established,and three models of cement-based composites with moisture content of w = 5%,w = 10%,w = 15% are established.Compared with the experimental data,the results show that when the moisture content of w = 15%,the numerical variation range of piezoresistive effect was the largest and the amplitude was the smallest,especially when the pressure was larger.Furthermore,the influence of pore water on the piezoresistive effect of carbon nanotube cement-based composites is highlighted.Considering the influence of carbon nanotube content,curing age and pore water content on the piezoresistive effect of carbon nanotube cement-based composites with pore water,different specimens were prepared through experiments to test the piezoresistive effect.The validity of piezoresistive effect theory was verified by numerical simulation.