Continuum Modeling of Nanocomposites with various Carbon Nanotube types Using F.E.M.

Carbon nanotubes (CNTs) are being used extensively as reinforcing materials at nanoscale in developing new nanocomposites, because of their excellent mechanical properties. Incorporating CNTs in polymer matrixes can potentially enhance the stiffness and strength of composites significantly when compared to those reinforced with conventional carbon fibers. To discover the ways for achieving this entails extensive experimental and simulation studies. Molecular dynamics (MD) simulations have been proved to be an excellent approach in characterizing nanocomposites. Nevertheless, MD is limited to nanoscale due to its extra-ordinary computational costs, which promoted the development and usage of alternate approaches for characterizing CNT reinforced composites at microscale. In this paper one of these alternative approaches, the continuum mechanics approach using the finite element method, is employed to estimate the effective modulus of CNT reinforced composites and was successfully validated using other analytical (rule of mixtures) and MD methods. Large-scale models were developed, simulating CNTs using pipe elements for the first time. Results from these models reveal that there exists a limiting value for the length of long CNT, for effective load transfer. It was also observed that composites reinforced with long CNTs yield very high effective modulus compared to those with short CNTs. These results are found to be in good agreement with those obtained using MD and multi-scale constitutive modeling approaches.