Thermal expanding behavior of carbon nanotube-reinforced metal matrix nanocomposites-A micromechanical modeling

Thermoelastic responses of carbon nanotube (CNT)-reinforced aluminum (Al) metal matrix nanocomposites (MMNCs) are studied comprehensively using an analytical micromechanical model. The effects of various parameters, including CNT volume fraction, cross-section shape, aspect ratio, directional behavior, non-straight shape, dispersion type, arrangement type, agglomerated state and generating the aluminum carbide (Al4C3) interphase between the CNT and Al matrix on the Al MMNCs coefficient of thermal expansion (CTE) are investigated. To verify the presented model for both aligned CNT-reinforced Al MMNC and randomly oriented CNT-reinforced Al MMNC systems, the predictions are well compared with the available experimental data in the literature. It is found that both cross-section shape and arrangement type of aligned CNTs do not affect the Al MMNC thermal expansion response. With increasing the CNT volume fraction, the transverse CTE of the aligned CNT-reinforced Al MMNCs increases up to the peculiar value and then decreases. However, the longitudinal CTE and the CTE of Al MMNCs containing randomly oriented CNTs continuously decrease by increasing the volume fraction. It is observed that the Al MMNC CTE is very sensitive to the CNT directional behavior, non-straight shape and the aspect ratio. The results indicate the CNT agglomerated state can degrade the Al MMNCs CTE.