New insights into interface interactions of CNT-reinforced epoxy nanocomposites

Interfacial shear strength between carbon nanotubes (CNTs) and polymer matrices is a fundamental but unresolved issue. Here, through molecular dynamics simulation (MD), we revealed that there are two completely different interfaces between CNTs and epoxy matrix, namely the weak interface (tau(emb)) at the embedded CNT region, and the strong pull-out interface (tau(pull-out)) occurred at the entry position of CNT. Strikingly, the load transfer capability at the CNT-embedded interface is very poor, yielding a low tau(emb) of similar to 6.8 MPa, which is one order of magnitude lower than that of the pull-out interface (tau(pull-out) similar to 132 MPa). Moreover, both of tau(emb) and tau(pull-out) depend on the diameters of CNT, but are not affected by CNT length. We also found that CNT defects, especially the topological defects such as CNT turns or kinks, are able to significantly increase the interfacial shear strength because of strong mechanical interlocking effect. Our results provide valuable insights into the CNT-polymer interface interactions, which are of great importance for exploring the reinforcing mechanisms for CNTs reinforced polymer nanocomposites.

Automated summary

Through molecular dynamics simulation, it was found that there are two different types of interfaces, weak and strong, between carbon nanotubes and epoxy matrices. The load transfer capability at the weak interface is very low, while the strong pull-out interface exhibits higher strength. Additionally, the interfacial shear strength is influenced by the diameter of the carbon nanotubes, but not by their length.