A Novel Technique to Simulate Reduced Residual Stresses in Laminated Composites Using Nanoparticles

Because of the natural inconsistency of mechanical and thermal properties of fiber and matrix, residual stresses are introduced during the curing process of fibrous polymer composites. Considering high Young’s modulus and negative coefficient of thermal expansion (CTE) of carbon nanotubes (CNTs), incorporation of CNTs into the matrix makes the matrix properties closer to the fiber ones and reduces residual stresses in laminated polymeric composites. In the present research, through a systematic theoretical study, effects of addition of small amounts of CNTs on micro- and macro-residual stresses in carbon fiber (CF)/epoxy laminates were investigated. First, micro-mechanics equations were employed to investigate CNTs effects on CTE and Young’s modulus of CNT/epoxy and CNT/CF/epoxy composites. Then, the micro- and macro-residual stresses were calculated using the energy method and classical lamination theory (CLT), respectively. The results indicate that addition of low amounts of the CNT causes the matrix CTE to decrease and the matrix Young’s modulus to increase, which in turn leads to a considerable reduction in micro- and macro-thermal residual stresses.