Computational prediction of waviness and orientation effects in carbon nanotube reinforced metal matrix composites

In carbon nanotube (CNT)-reinforced metal matrix composites (MMCs), most of the reinforcement is observed to be located at grain boundaries. The orientation and waviness of CNT will vary with the matrix grain shape and size. In this paper, the elastic modulus and local stress distribution of MMCs with nonstraight shape of CNT are investigated by adopting the finite element method (FEM) and a micromechanical model. In MMCs, each wavy CNT is treated as a cord including a sequence of small straight segments. The results of FEM simulation lie close to that evaluated from the micromechanical model and the experimental data. The variations of elastic modulus of MMCs with total numbers of small segment for different microstructures of the composites have been analyzed. A conclusion can be obtained that the effect of CNT waviness on the elastic properties of MMCs reinforced with randomly distributed CNT is slight. The influence of orientation of small segments on the stiffening effect of the reinforcement is also discussed. In addition, the introduction of CNT into MMCs can obviously affect the local stress field of the composites.