Investigation of Mechanical and Thermal Properties of Polymer Composites Reinforced by Multi-Walled Carbon Nanotube for Reduction of Residual Stresses

The micromechanical models are used to investigate mechanical and thermal properties of a polymer matrix nanocomposite containing multi-walled carbon nanotubes (MWCNT) in their effects to reduce residual stresses in nanocomposites. To do this، first nanotubes with different weights and volume fractions were dispersed in ML-506 epoxy resin. By using different micromechanical models، the effect additional nanotubes on elastic modulus and coefficient of thermal expansion (CTE) of nanotubes/epoxy were studied as critical parameters. Comparing the model and available experimental results، the modified Halpin-Tsai model and the modified Schapery model were chosen to calculate the mechanical and thermal properties of the nanocomposites. Then، using the matrix reinforced with MWCNT and classical micromechanics models the elastic modulus and coefficients of thermal expansion of the nanocomposites were determined for a single orthotropic ply. The results showed that the rule of mixture (ROM) and Hashin-Rosen model to determine the longitudinal and transverse elastic moduli and Van Fo Fy model to calculate the coefficient of thermal expansion were in good agreements with the experimental results of a single-layer nanocomposite. Finally، the classical laminated plate theory (CLPT) was used to calculate the residual stresses of the CNT/carbon fiber/epoxy composites with different weights and volume fractions of MWCNT for angle-ply، cross-ply and quasi-isotropic laminated composite materials. The results showed that residual stresses were reduced using a maximum of 1% wt or 0. 675% volume fraction of the MWCNT in polymer composites. Also، the highest reduction in residual stresses was observed in [02/902] cross-ply laminated composite materials.