In the present study 3D finite element (FE) analysis has been used to evaluate Young's modulus, shear modulus and coefficient of thermal expansion (CTE) of single-walled carbon nanotubes (SWCNTs). Both armchair and zigzag SWCNTs have been analyzed and some important observations have been made in regard to dependence of elastic moduli and CTE of SWCNTs on important parameters.

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Multi-scale finite element analysis has been performed for determination of longitudinal and transverse Young's moduli of carbon nanotube (CNT)-reinforced alumina matrix nanocomposites considering a square representative volume element (RVE). The square RVE has been used to simulate the stress redistribution around a broken CNT at the interface of CNT and matrix, and ineffective length of the broken CNT has been determined. It has been observed that ineffective length of the broken CNT does not show sufficient dependence on the volume fraction. It is also been observed that high magnitude of interfacial shear stress around the broken CNT exists indicating the chances of fiber debonding.

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In the present work, multi-scale finite element analysis of carbon nanotube/epoxy composites having a broken carbon nanotube has been performed to assess the severity of such a fiber (i.e. carbon nanotube) break. A square representative volume element having nine-carbon nanotubes has been considered for the analysis. Considering a small debonding around the broken fiber as a crack front, stress redistribution around the break is studied. Using the concept of linear elastic fracture mechanics, strain energy release rates around the debonding have been calculated using virtual crack closure integral method. Quadratic stress criterion has been used to assess the delamination initiation at the interface of broken carbon nanotube and the matrix. Virtual crack closure integral along with quadratic stress criterion has been used to determine the critical strain energy release rate. Results from the present analysis show that the fiber volume fraction does not have significant influence on the ineffective length of the broken carbon nanotube. A high magnitude of interfacial shear stress is observed to have developed in the vicinity of the fiber break indicating the chances of debonding. All the three components of strain energy release rate have been determined and the influences of important parameters on the value of strain energy release rate have also been studied.

A comparative study of elastic properties and mode I fracture energy has been presented between conventional carbon fibre (CF)/epoxy and advanced carbon nanotube (CNT)/epoxy laminated composite materials. The volume fraction of CNT fibres has been considered as 15%, 30%, and 60% whereas; the volume fraction of CF has been kept constant at 60%. Three stacking sequences of the laminates viz.[0/0/0/0], [0/90/0/90] and [0/30/–30/90] have been considered in the present analysis. Periodic microstructure model has been used to calculate the elastic properties of the laminated composites. It has been observed analytically that the addition of only 15% CNT in epoxy will give almost the same value of longitudinal Young’s modulus as compared to the addition of 60% CF in epoxy. Finite element (FE) analysis of double cantilever beam specimens made from laminated composite has also been performed. It has been observed from FE analysis that the addition of 15% CNT in epoxy will also give almost the same value of mode I fracture energy as compared to the addition of 60% CF in epoxy. The value of mode I fracture energy for [0/0/0/0] laminated composite is two times higher than the other two types of laminated composites.