Micro-Crack Bridging Effects on the Tensile and Compressive Strengths of CNT-Epoxy Composites.

Micro-crack bridging and an optimal regime for dispersion of carbon nanotubes (CNTs) in the E-glass fabric reinforced polymer (GFRP) matrix are considered. The purpose of CNT dispersion in the glass fabric is to achieve the enhanced mechanical and tunable thermal/dielectric properties. The requirement for such conducting composites compared to high-cost carbon fabric is well recognized. The results are validated with the help of a theoretical model. The model relates the stiffness degradation of the composites and the existence of matrix cracks in the composites. Finite element simulation of a representative volume element of a laminate shows the effect of CNTs on the micro-cracks and the effective stiffness. The results obtained from the theoretical and finite element simulations are correlated to the experimental data and explain the increased strength due to the addition of CNT. This study shows that certain processing conditions in combination with the effect of dispersant agents reduce the porosity, residual stress and present a consistent dispersion strengthening effect with as low as 0.1 wt% CNT addition, resulting in improved tensile and compressive properties. The treatment of CNTs with ethanol reduces the Van der Waals forces among CNTs and the epoxy matrix viscosity. Enhancement in the CNT-GFRP stiffness and strength appears primarily due to effective micro-crack bridging and changes in the load transfer path. [ABSTRACT FROM AUTHOR]