13th International Conference on Fracture June 16–21, 2013, Beijing, China Research on the mechanical properties of the CNT composites Luodan Su, Qingsheng Yang* Department of Engineering Mechanics, Beijing University of Technology, Beijing 100124, China *Corresponding author: qsyang@bjut.edu.cn Abstract Carbon nanotube (CNT) can be used as a good reinforcement embedded into polymer matrix. However, properties of composites reinforced by CNT can’t be improved efficiently, because of the damage of interface between CNT and polymer in CNT composites. In this paper, the cohesive zone model (CZM) was employed to express the damage and fracture of interface between CNT and the epoxy matrix. The key parameters of the bilinear CZM were deduced based on the existing theory work. The whole deformation and fracture process of the interface has been revealed through the FE simulation results. The performance of the interface decides the mechanical property of the CNT composites and the stress-strain curve of composites has been plotted. It is with great importance to study the mechanical property of the interface to improve the performance of CNT composites. Keywords Carbon nanotude, Composite, Interface, Damage, Crack Growth 1. Introduction Since the discovery of carbon nanotube (CNT) by Iijima [1], CNT has wide application potential because of their wonderful physical and mechanical property, it has been thought as a promising candidate as the ideal reinforcing fibers for advanced composite with high strength and low density. However, mechanical property of composites reinforced by CNT can’t be improved efficiently, owing to the deep affect of interface between CNT and polymer in CNT composites. The damage and fracture of the interface leads to stress redistribution in CNT composite, and decides the effective mechanical property of the composite. The mechanical property of the interface is the key factor of the CNT reinforced composite [2]. The Cohesive zone Model (CZM) describes material separation with a traction-separation law (T-S law) and links the micro-structural failure mechanism to the effective properties of the composite [3,4]. Because of the nano-scale interface in CNT composite, the van der Waals force plays an important role in the property of the interface [5,6]. The Cohesive zone Model(CZM) can reflect the characteristic and working principles of the van der Waals force phenomenologically, by two important parameters, the cohesive strength Tc and the energy release rate Gc, as shown in Fig.1[7]. The effective separation and damage parameter from view point of stiffness reduction are employed. The different T-S law has been developed with continuous study of the cohesive model, and the CZM has been widely used in interface decohesion and crack growth. Figure 1. Bilinear cohesive law Nowadays, many researchers have realized the significance of the van der Waals force in the
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