The role of carbon nanofibers on thermo-mechanical properties of polymer matrix composites and their effect on reduction of residual stresses

In this research, the effects of carbon nanofibers (CNFs) on thermo-elastic properties of carbon fiber (CF)/epoxy composite for the reduction of thermal residual stresses (TRS) using micromechanical relations were studied. In the first step, micromechanical models to calculate the coefficient of thermal expansion (CTE) and Young's modulus of CNF/epoxy and CNF/CF/epoxy nanocomposites were developed and compared with experimental results of the other researchers. The obtained results of the CTE and Young's modulus of modified Schapery and Halpin-Tsai theories have good agreement with the experimental results. In the second step, the classical lamination theory (CLT) was employed to determine the TRS for CNF/CF/epoxy laminated nanocomposites. Also, the theoretical results of the CLT were compared with experimental results. Finally, reduction of the TRS using the CLT for different lay-ups such as cross ply, angle ply, and quasi-isotropic laminates were obtained. The results demonstrated that the addition of 1% weight fraction of CNF can reduce the TRS that the most reduction occurred in the unsymmetric cross-ply laminate by up to 27%.