The effect of nanotubes waviness on mechanical properties of CNT/SMP composites

In this paper, the effects of inclusion waviness and its distribution to the effective carbon nanotubes (CNTs)/shape memory polymer (SMP) composites stiffness is investigated. A micro mechanical model is developed to take into account the waviness effect of nanotubes, which are assumed as solid short fibers with a circular cross-section and exhibiting bow shape waviness. The mechanical properties of the composite are significantly increased by reinforcing with CNTs and the desired mechanical properties in addition to proper shape recovery behavior are obtained. The improvements in modulus are remarkably less than the micromechanical prediction assuming straight nanotubes. It is shown that the lack of fiber waviness distribution assumption was found to lead to inaccurate composite stiffness prediction. Since the effects of CNT waviness and aggregation in the composite frequently encountered in real engineering situation, in this study the effects of these defects on the overall properties of the CNT/SMP composite are simultaneously examined. The results indicate that both the waviness and aggregation can drastically reduce the stiffening effect of the CNTs and are two important factors influencing the reinforcing efficiency.