Micromechanical analysis of carbon nanotube-coated fiber-reinforced hybrid composites

A multiscale micromechanical modeling approach is developed to predict elastic properties of carbon fiber (CF)-reinforced polymer hybrid composites. In this type of hybrid composite, the unidirectional fibers are coated with randomly oriented carbon nanotubes (CNTs). Two fundamental aspects affecting the mechanical behavior of the hybrid composites are investigated herein; namely, CNT non-straight shape and the existence of an interphase region between a CNT and the polymer matrix. An excellent agreement is observed between the predictions of the new micromechanical method and available experimental data. The results reveal that for an accurate prediction of the elastic properties of the CNT-coated CF-reinforced hybrid composite, the consideration of waviness and transversely isotropic behavior of CNT, CNT/polymer interphase region and random arrangement of CFs is essential. It is found that the contribution of CNTs to the elastic response of the hybrid composite in longitudinal direction can be neglected. However, transverse elastic modulus of the CNT-coated CF-reinforced hybrid composite is significantly improved over that of the conventional CF-reinforced composite without CNT coating. Also, the maximum value of transverse elastic modulus can be obtained when the uniformly aligned straight CNTs are radially grown on the surface of the horizontal CFs.