Modelling evidence of stress concentration mitigation at the micro-scale in polymer composites by the addition of carbon nanotubes

A versatile two-scale model was developed to investigate the use of carbon nanotubes for re-distribution and, eventually, suppression of stress concentrations on the micro-level in fiber-reinforced composites. With this model a variety of CNT assemblies could be generated including CNTs dispersed in the matrix, grown on fibers or spatially organized in a network. The presence of CNTs in a composite was found to induce strong heterogeneity in stress fields. CNTs grown on fibers were shown to suppress stress concentrations at the fiber/matrix interface but to increase stresses in resin rich zones between the forests. Agglomerated CNTs were found to behave as stiff microscopic particles leading to additional stress magnification. A promising way to suppress stress concentrations without affecting stresses in the rest of the matrix was to position CNTs in a network that is interdependent with fiber positions.