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

This work provides a comprehensive and comparative study on the interfacial load transfer properties of aminofunctionalised 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.

Automated summary

This study comprehensively compared the interfacial load transfer properties of aminofunctionalized carbon nanotube (CNT)/epoxy composites using molecular dynamics simulations. The introduction of amino functional groups was found to enhance interfacial shear strength, especially when considering crosslinking interactions. Additionally, significant load transfer interactions between the end of CNTs and the matrix were observed at the nanoscale, challenging the classical shear lag model assumption of zero traction between fiber ends and matrix.