The Interface Stress Analysis Of Carbon Nanotube Reinforced Composites Based On Shear Lag Model

Carbon nanotubes (CNTs) reinforced composites are the focus of current researchin materials science. The key factor of reinforcement is the load transferring of theinterface of different materials. Further study of the composites interfacial stress willpromote its development and application. When dealing with the contact surface of theCNTs and matrix, there is perfect bonding assumption in the interface and only axialnormal stress subjected to the ends of the representative volume element (RVE), whichare not entirely in accordance with the actual situation. Therefore, this thesis establishesa shear lag model considering the effects of the axisymmetric uniform shear stress onthe outer surface of the RVE and the imperfect bonding, which are more close to theactual situation. The model of the CNTs reinforced matrix composites is alsoestablished by the finite element method, the finite element calculate the effects of thesurface shear stress of the matrix and the apparent rate on the interfacial stress of theRVE. The results of the finite element compare with the established shear lag modelsand we found that the shear lag modelâ… andâ…¡can effectively predict the numericalresults. The following are main conclusions:(1) Using the shear lag models of the RVE is obtained: the outer surface of the RVEsubjected to shear stress more effective than only by the axial normal stress of its endsthe role. So we prevent or reduce the surface of the composite subjected to shearloading as far as possible, otherwise it is easy to make structural limit load anddestroyed. If adding the right amount of nanotubes in the matrix, that can help thematrix good resist to external shear loads.(2) The contact degree and friction coefficient play an important role in the CNTsreinforced composites. In the process of making CNTs and matrix binding, the contactsurface of the CNTs and the matrix can reach nearly perfect bonding, even if the frictioncoefficient of the contact surface is relatively smaller, CNTs are still able to play a goodrole in enhanced matrix.(3) The huge apparent rate of the CNTs makes the matrix in the composites carrygreater external loads, but when the apparent rate of the CNTs reaches a certain value,the axial normal stress of the CNTs reinforced matrix composites tends to a constantvalue.(4) The numerical model of the CNTs reinforced matrix composites is established by the finite element software, The results of the finite element compare with theestablished shear lag models and we found that the shear lag modelâ… andâ…¡caneffectively predict the numerical results..