Mechanical Properties Research Of Carbon Nanotube Reinforced Composites

Carbon nanotubes are widely used in composite materials for its excellent mechanical properties. While adding carbon nanotubes to matrix makes the interface between the matrix and carbon nanotubes a big problem. The interface properties and carbon nanotubes arrangement become the important factors to the carbon nanotube composite materials mechanics performance. In this paper, carbon nanotube composite material was detailedly investigated. Material effective modulus prediction, nano-structure failure process and composite materials macroscopic failure process were studied respectively. The specific work is as follows:1. Python scripts in ABAQUS were adopted to establish the quadrilateral representative volume element model under the displacement boundary conditions, which contains matrix, interface and carbon nanotubes. The prediction of composites effective modulus was based on the mesoscopic mechanics of composite material. The results were compared with the traditional method, and the feasibility of the method in this paper was proved. Also the influences of the interface thickness, interface elastic modulus and carbon nanotube length-to-diameter ratio were analyzed.2. The carbon nanotube composite’s nanostructure failure process was studied. The model was established by using the technology of cohesive element and user-defined field in ABAQUS. Transverse load and longitudinal load were considered respectively, then the strength of the composite under different loads was predicted and the nanostructure failure process was tried to be explained. It was found that under transverse load, the initial damage area started from the part of the interface that along the load direction, and gradually extended vertically to the nearby matrix. The matrix failure started prior in the smallest gap between two nanotubes. As the load increased, the failure region extended parallelly. The final failure region appeared to be the Chinese letter "一", which was vertical to the transverse load. Under the longitudinal load, the bearing capacity of the matrix was quite limited. Carbon nanotubes properties became the decisive factor of the composite longitudinal properties.3. The composite material macroscopic failure process was studied by the theory of material limited degradation. The fiber reinforced composite NOL ring model was established by Tsai-Wu failure criterion. The results of NOL ring tensile test and finite element simulation were compared. It was found that the failure process of the NOL ring under tensile load was more complex than the failure process of a single direction carbon fiber composite material plate. The tensile force-displacement curves of finite element simulation and tensile test were consistent. It proved the feasibility of the finite element method and its engineering significance.