Determination and Reducing of Curvature from Residual Stresses in Cured Shapes by Using Carbon Nanotubes in Unsymmetric Carbon/Epoxy Laminates

In this research, the determination of curvature and the effect of carbon nanotubes (CNTs) on it in cured three-phase un-symmetric cross-ply composite laminate have been studied. The un-symmetric cross-ply composite laminates is including three different phases: carbon fiber, polymer epoxy and carbon nanotube particles that different volume fraction of CNTs including %0, %1, %2 and %3 have been considered. Different micromechanical models such as Halpin-Tsai, bridging and Schapery models have been used to determine the mechanical and thermal properties. Adding of %1 volume fraction of CNTs has been caused decreasing the longitudinal and transverse coefficient thermal expansions and increasing the longitudinal, transverse and shear modulus ones. Developed Hyer model's has been employed to investigate different parameters such as curvature, critical length and deformed shape in different lengths of square un-symmetric cross-ply laminates. Addition of 1% volume fraction of CNTs decreases the critical length and curvature about 9% and 14%, respectively. In addition, the results of finite element analysis have been compared with the developed Hyer model and showed less than 10% error.