Issue 33

C. Gao et alii, Frattura ed Integrità Strutturale, 33 (2015) 471-484; DOI: 10.3221/IGF-ESIS.33.52 471 A new micromechanical model of CNT-metal nanocomposites with random clustered distribution of CNTs Chongyang Gao, Yu Lu School of Mechanical Engineering, Zhejiang University, Hangzhou 310027, China corresponding author: gcysci@163.com Y.T. Zhu 2School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China A BSTRACT . Uniform dispersion of carbon nanotubes (CNTs) is a key issue for utilization of their reinforcement potential in CNT-reinforced metal matrix nanocomposites (MMNCs). It was reported that CNT clusters often exist in MMNCs prepared by various techniques, which reduces the load transfer efficiency between the matrix and reinforcement. In this paper, a new micromechanical constitutive model of CNT-reinforced MMNCs is developed, which takes into account of the influences of CNT clusters and misorientations. The strength values of a CNT/Al nanocomposite predicted by the new model are compared first with experimental data for validation. Then, the developed model is applied to predict the size effect, temperature effect and strain rate effect of the nanocomposite in its overall elastoplastic response. K EYWORDS . Micromechanical modelling; Metal matrix nanocomposites; Carbon nanotubes; Cluster effect; Misorientation angle. I NTRODUCTION n recent years, it has been reported that incorporating carbon nanotubes (CNTs) into polymers [1-3], ceramics and metals [4-7] can dramatically improve their mechanical properties. This is due to the high strength; high Young’s modulus and super thermal conductivity of CNTs. Metal matrix nanocomposites (MMNCs) reinforced with CNTs have enhanced yield strength and a low thermal expansion coefficient, which render them substantial potential in some weight sensitive applications such as aerospace structures [8]. Yang et al. [9] demonstrated that the yield strength of a 1.5 wt. % CNT/Al nanocomposite produced by an improved chemical vapor deposition (CVD) is 2.2 times that of the pure aluminum, while the result obtained in compression tests [10] is not so high due to different preparation technique of the sample. Kim et al. [11] showed that the measured tensile strength of CNT/Cu nanocomposite with 10 vol. % CNTs is 281MPa, which is approximately 1.6 times higher than that of unreinforced pure copper. Li et al. [12] made CNT- nanocrystalline Cu nanoacomposite using ball-milling and high-pressure torsion consolidation, which has very high yield strength of 1100 MPa at 1 wt% CNT addition. Thus, CNTs can be an ideal reinforcement for material design to improve mechanical properties of composites. The high aspect ratio of length to diameter of curved CNTs makes them prone to entangle with each other resulting in clustering in matrix, and consequently difficult to be uniformly dispersed in matrix. To solve this problem, various preparation techniques have been employed to achieve a more uniform distribution of CNTs in MMNCs so as to realize I