Computational Prediction of Mechanical Properties of PA6–Graphene/Carbon Nanotube Nanocomposites

Abstract

Polyamide 6 (PA6) is a popular semicrystalline thermoplastic with good strength, stiffness, mechanical damping, wear resistance, and an excellent performance-to-cost ratio. Performance of PA6 materials can be improved with the inclusion of graphene (G) and carbon nanotubes (CNT). In this study, molecular dynamics (MD) simulations with INTERFACE and reactive INTERFACE force fields (IFF and IFF-R) were used to predict the mechanical response of amorphous PA6−CNT/G nanocomposites as a function of CNT/G loading. The mechanical property predictions for both PA6−CNT and PA6−G nanocomposites were largely similar for both bulk and Young's moduli despite a significantly greater interaction per atom between G and the PA6 matrix. The simulation conditions during polymerization (such as NVT vs NPT ensemble) have a significant effect on the predicted mechanical properties; the presence of voids may not have a detrimental effect on the mechanical response if the voids are evenly distributed throughout the nanocomposite. To validate the MD predictions, PA6−CNT/G thin films were prepared and tested for Young's modulus. The predicted values of Young's modulus agree moderately well with the experimental values; discrepancies can be attributed to the factors of a thin film vs a bulk solid, agglomeration, and crystallinity.

Reactive Molecular Dynamics Simulation of Epoxy for the Full Cross-Linking Process

“…IFF-R replaces the traditional harmonic bond-stretching potential with a morse potential to model covalent bond dissociation in response to large local mechanical deformations. Pisani et al 30 used IFF-R to simulate polyamide nanocomposites, and Odegard et al 31 demonstrated the capability of IFF-R for accurately predicting mechanical properties of fully cured epoxy systems. However, IFF-R has not yet been used to simulate partially cured epoxy systems.…”

Multiscale Modeling of Polyamide 6 Using Molecular Dynamics and Micromechanics

“…Unless otherwise stated, all visualizations of the atomic structure were performed with the OVITO software . The nonreactive class 2 INTERFACE force field (IFF) was used for densifying, polymerizing, and equilibrating the PA6 systems. , The recently developed reactive IFF or IFF-R was used for the deformation simulations. − IFF-R incorporates the Morse potential for fast, accurate bond scission capabilities useful for large deformations.…”

Physically soft magnetic films and devices: fabrication, properties, printability, and applications

“…Therefore, very often molecular dynamics (MD) simulations have been employed to capture the interactions between the NPs and the polymeric material (in both uncured and cured states). 75,[79][80][81][82][83][84][85][86][87][88][89][90][91][92] Typically, these interactions consist of non-bonded van der Waals (vdW) and electrostatic interactions: for cases where these interactions cannot be obtained from a priori known force fields, one needs to employ ab initio MD simulations for obtaining these force fields. 75 These intermolecular interactions dictate the NP dispersibility inside the surrounding polymer structure.…”

“…A detailed understanding of the non-bonded interactions is crucial for modulating such behavior, which in turn dictates the overall properties of the nanocomposites. MD simulation studies have shed light on a variety of issues such as (a) the distribution of polymeric chains around the NPs, 81 (b) the dynamics (e.g., diffusivity) and mean distribution of the NPs inside the polymeric matrix (both in entangled and nonentangled states), 82 (c) the effect of NP functionalization on the polymer structure and dynamics, 83 and (d) the average properties of the nanocomposite, such as the elasticity, 84 thermal conductivity, 85 glass transition temperature, 86 adhesive properties, 87 bulk and Young's moduli, 88 load transfer capabilities, 89 creep properties, 90 self-healing behavior 91 (such average properties are generated by appropriate post-processing of the trajectory data for the polymeric material and the NPs), etc.…”