Study of glass transition temperature (T_g) of novel stress-sensitive composites using molecular dynamic simulation

Abstract

This study investigates the glass transition temperature (T g) of novel stresssensitive composites capable of detecting a damage precursor using molecular dynamics (MD) simulations. The molecular structures of a cross-linked epoxy network (which consist of epoxy resin, hardener and stress-sensitive material) have been simulated and experimentally validated. The chemical constituents of the molecular structures are di-glycidyl ether of bisphenol F (DGEBF: epoxy resin), di-ethylene tri-amine (DETA: hardener) and tris-(cinnamoyloxymethyl)-ethane (TCE: stress-sensitive material). The crosslinking degree is varied by manipulating the number of covalent bonds through tuning a cutoff distance between activated DGEBF and DETA during the non-equilibrium MD simulation. A relationship between the cross-linking degree and T g s has been studied numerically. In order to validate a proposed MD simulation framework, MD-predicted T g s of materials used in this study have been compared to the experimental results obtained by the differential scanning calorimetry (DSC). Two molecular models have been constructed for comparative study: (i) neat epoxy (epoxy resin with hardener) and (ii) smart polymer (neat epoxy with stress-sensitive material). The predicted T g s show close agreement with the DSC results.

Multiscale Modeling of a Mechanophore-embedded Nanocomposite for Damage Initiation Detection

“…Figure 1 shows that multiscale modeling framework will mimic the experimental process by simulating the epoxy curing process for thermoset polymer and the UV dimerization process for the smart material. The epoxy curing process was successfully implemented by the authors' previous work [17]. A numerically dimerized system has been performed to simulate mechanophore activation under tensile loading condition.…”

“…A detailed procedure to estimate the most likely cross-linking degree is outside of the focus of this study. According to the authors' previous study [17], the cross-linking degree of TCE-embedded nanocomposite has been determined to be 52.6%. The numerical dimerization process has been performed with the epoxy curing process to construct cyclobutane structure in the thermosetting matrix.…”

“…Merck molecular force field (MMFF) has been used as a classical force field [16]. In a recent study, the authors estimated the cross-linking degree of TCE-embedded nanocomposite stochastically, and the MD simulation unit cell was constructed using the estimated cross-linking degree [17]. A local force analysis is now performed under uniaxial loading; the results are expected to provide a guideline for improving the design and synthesis of the novel polymer system.…”

Atomistically derived cohesive behavior of interphases in carbon fiber reinforced CNT nanocomposites

“…This paper presents a methodology to characterize the interface between the fiber and the CNT-dispersed epoxy polymer in nanocomposites by integrating an atomistic model with a continuum model. As previously stated, MD simulations have tremendously contributed to the study of physical and chemical interactions in multiphase materials [23][24][25]. However, the high computational cost associated with the atomistic simulations limits their use beyond the nanoscale.…”

Atomistically informed stochastic multiscale model to predict the behavior of carbon nanotube-enhanced nanocomposites

“…Subramanian et al. [12] and Koo et al [13] recently introduced an approach to stochastically simulate the chemical curing process in epoxy polymers through MD simulations. The authors studied the effect of the polymer cross-linking degree on the mechanical properties of a smart polymer.…”