Molecular simulations of the influence of defects and functionalization on the shear strength of carbon nanotube-epoxy polymer interfaces

X Peng and SA Meguid, COMPUTATIONAL MATERIALS SCIENCE, 126, 204-216 (2017).

DOI: 10.1016/j.commatsci.2016.09.026

Unlike earlier studies, which focused on thermoplastics, in this work attention is devoted to carbon nanotube (CNT) reinforced thermoset polymer composites. Specifically, extensive molecular dynamics (MD) simulations were conducted to study the effect of defects and functionalization on the interfacial shear strength (ISS) of carbon nanotube-epoxy composites before and after cross-linking. Three main types of defects (vacancies, adatom, and Stone-Wales (SW)) as well as phenyl functional group were considered in a representative volume element (RVE). The RVE comprised a single-walled CNT embedded in an epoxy matrix, and consistent valence force field (CVFF) was used in all MD simulations. Our results reveal that (i) vacancy defects degrade the ISS, and that the degradation effects depend predominantly on the number of missing atoms and not on the type of vacancy defects, (ii) adatom defects have a marginal effect on the ISS, (iii) SW defects promote greater ISS of cured systems, (iv) phenyl groups dramatically increase the ISS of cured systems, and (v) uncured systems experience lower ISS which is not affected by the number and type of defects and functionalization. The findings of this study will assist in improving our understanding of the operating toughening/weakening mechanisms and the load transfer capability in epoxy-based nanocomposites. (C) 2016 Elsevier B.V. All rights reserved.

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