The interfacial load-transfer enhancement mechanism of amino-functionalised carbon nanotube reinforced epoxy matrix composites: a molecular dynamics study

Abstract This work provides a comprehensive and comparative study on the interfacial load transfer properties of amino-functionalised carbon nanotube (CNT)/epoxy composites via molecular dynamics simulations. Three models were constructed: (i) a pristine CNT embedded in epoxy resin, (ii) an amino-functionalised CNT embedded in epoxy resin without crosslinking interactions between amino groups and the epoxy resin matrix, and (iii) an amino-functionalised CNT embedded in epoxy resin with crosslinking interactions. The pull-out process was simulated using a steering molecular dynamics simulation to examine the sidewall load transfer effect of the CNTs. The travelling of amino groups along the CNTs was simulated by changing the topology of the functionalised CNT using a polymer consistent force field during the pull-out process. The mean interfacial shear stress, pull-out energy, stress, and atomic displacement were analysed. The results show that the interfacial shear strength as well as the compatibility and cooperativity between the CNTs and the matrix can be efficiently enhanced by introducing amino functional groups. In particular, a dramatic enhancement can be obtained by considering the crosslinking interactions. In addition, the interfacial load transfer between the end of the CNTs and the matrix was studied. The axial normal stress at the end of the CNTs was calculated by placing one diglycidyl ether bisphenol A molecule near the end of the CNT. The results show that there was a large interaction between the end of the CNTs and matrix, which cannot be neglected. Thus, the assumption of zero traction between the fibre end and matrix in the classical shear lag model should be modified at the nanoscale.