An analytical solution on interface debonding for large diameter carbon nanotube-reinforced composite with functionally graded variation interphase

A three-dimensional (3D) analytical solution is derived for homogeneous cylinder with the functionally graded variation interphase (FGVI) at the inner surface. Based on the 3D solution, the dilute solution-based homogeneous model is adopted for the carbon nanotube (CNT)-reinforced nanocomposite considering FGVI and effective fibre modulus, in which the van der Waals-based cohesive law is adopted for the connection between CNT and the interphase. Parametric studies demonstrate that: (1) FGVI increases the composite stiffness, while it leads to the earlier debonding of the cohesive interface. (2) The peak strength of the macroscopic stress-strain is greatly influenced by the cohesive strength at the interface, higher cohesive strength leads to higher macroscopic peak strength. (3) The peak strength of the macroscopic stress-strain relation is underestimated without considering the effective fibre modulus, and the influence of the effective FGVI modulus is larger than that of the effective fibre. (4) CNTs of the large diameter bring the stress drop at a very small strain, especially for the large volume fraction of CNT.