An analysis of the factors affecting strengthening in carbon nanotube reinforced aluminum composites

Tensile strength data of Al/CNT composites from the literature is analyzed to understand the effects of CNT dispersion, processing technique, degree of deformation and CNT-matrix interface on the elastic modulus, strength and toughness of composites. Strengthening can be divided in three regimes which show decreasing strengthening effect with an increasing CNT content. The strengthening is highest for CNT content less than 2 vol.%. The applicability of the micromechanics models in predicting the strength and elastic modulus of CNT reinforced metal matrix composites is also analyzed. The rule of mixtures is effective in predicting the elastic modulus of the Al/CNT composites for low CNT content (<2 vol.%) whereas Halpin-Tsai and combined Voigt-Reuss models are better at intermediate CNT content (2-5 vol.%). Effect of degree of deformation such as extrusion ratio during processing on the load transfer to CNT and resulting strengthening is also discussed. Tensile data on Cu/CNT and Mg/CNT composites is compared with Al/CNT to show that strengthening is not effective when there is no chemical interaction between metal matrix and CNT. The analysis presented here would be very helpful in the future design of high strength CNT/metal matrix composites. (C) 2010 Elsevier Ltd. All rights reserved.