Effect of crack and determination of fracture energy of carbon nanotube-reinforced polymer composites

Carbon nanotube fillers in polymers are quite effective compared to traditional carbon black micro particles, primarily due to their high aspect ratios. Increasing attention is being focused on the carbon nanotube surface, namely, the interface between the carbon nanotube and the surrounding polymer matrix. From micromechanics, it is through shear stress build-up at this interface that stress is transferred from the matrix to the carbon nanotube. Because of the dissimilarity in elastic properties of polymer matrix and carbon nanotube, there will usually be some asymmetry near the crack tip even if the geometry and loading are symmetric and interface cracks tend to be mixed mode. In this article, the effect of crack on the interface of polymer matrix and carbon nanotube is analysed using both analytical and extended finite element method. The delamination is modelled as an interface crack problem and stress intensity factor and energy release rate is calculated as a function of crack length and stiffness ratio of matrix and carbon nanotube.