Two modified multiscale modeling approaches for determination of two-phase and hybrid nanocomposite properties

Abstract

In this paper, mechanical properties of thermoset epoxy based two-phase and hybrid nanocomposites containing carbon nanotubes (CNTs), and carbon nano diamond particles (CNPs) are determined using two different multiscale modeling approaches. The effects of resin crosslinking, interphase mechanical properties, and filler agglomeration on nanocomposite mechanical properties are investigated. First, the crosslinking between Diglycidyl ether of bisphenol A (DGEBA) resin and Diethylenetriamine (DETA) hardener is modeled considering different crosslinking forms and ratios using molecular dynamics (MD) simulations. Results indicate that resin elastic modulus increases with increasing the crosslinking ratio especially above 75%, but crosslinking form has an insignificant effect on resin modulus. Next, different nanofillers and their interphases are modeled using MD simulations to determine the representative volume element (RVE) and the effective fiber sizes and mechanical properties. The thickness of the interphase for each nano filler type is determined from the radial distribution function (RDF) diagram in order to determine the effective fiber volume more realistically. Then, the general Halpin-Tsai model is modified by adding an interphase volume factor and is used to determine two-phase and hybrid nanocomposite mechanical properties using effective nano filler properties. In addition, a new numerical multiscale modeling technique was developed which uses the MD-determined effective filler properties along with finite element method (FEM) to determine nanocomposite mechanical properties. Nanocomposites reinforced with aligned and randomly oriented reinforcements are modeled. Good agreement is observed between the two multiscale modeling techniques for the two-phase nanocomposite mechanical properties. Finally, the effect of filler agglomeration on nanocomposite properties is investigated. The results indicate that agglomeration decreases elastic modulus of CNT/epoxy nanocomposite. However, agglomeration does not have a significant effect on elastic modulus of CNP/epoxy nanocomposite.