Investigation into the influence of CNTs configuration on the thermal expansion coefficient of CNT/Al composites

A 3D representative volume element (RVE) model was developed to analyze the effective thermal expansion coefficient (CTE) of carbon nanotube reinforced aluminum (CNT/Al) composites. The influences of geometric configuration, orientation and volume fraction of CNTs on CTE of the CNT/Al composites were investigated. The results show that the orientation of CNTs significantly influences the stress and strain distributions around CNTs, and when CNTs are parallel to the load direction, the constraint effect of CNTs on the matrix is the largest. Furthermore, the configuration of CNTs also plays an important role in reducing thermal expansion behavior of CNT/Al composites, and the bundled configuration exhibit the lowest CTE. In particular, with the increase of the number of CNTs in each bundle, the CTE decreases and then tends to be unchanged. When the volume fraction of CNTs is 5%, and the number of CNTs in each bundle is 25, the CTE of the composite reaches 5.12 × 10−6/°C, which is 76% lower than the CTE of the matrix. A linear decrease of the CTE of CNT/Al composites is observed as the CNT volume fraction increases. Overall, this work establishes a comprehensive understanding of factors affecting the CTE, and the obtained findings could provide a good theoretical basis for designing low CTE CNT/Al composites.