Molecular Simulation of Mechanical Properties of Hyperbranched Epoxy Resin Composites

This research employed molecular dynamics (MD) simulations to study the modification of epoxy resin composite materials using bisphenol A diglycidyl ether (DGEBA) branched molecules and hexahydrotriazine hyperbranched epoxy resin (HHTE1) molecules. The objective was to analyze the impact of structural dimensionality as well as alterations in branching of the material on its mechanical properties. Comparing to those of linear structures (PL), the Young's modulus (E), bulk modulus (K) and shear modulus (G) of two-dimensional planar materials (PN) slightly increased by 0.52%—1.61%, 0.28%—1.04%, and 1.01%—2.89%, respectively. In contrast, transitioning from PN to three-dimensional structures (PF) resulted in decreases in E, K, and G by about 1.52%—3.33%, 1.05%—4.35%, and 2.30%—3.13%, respectively. Comparatively, materials modified with HHTE1 hyperbranched molecules exhibited significantly improved mechanical properties with the E, K, and G enhanced by about 5.56%—11.90%, 4.86%—10.86% and 5.59%—10.74%, respectively, compared to those with DGEBA branching. The materials model established in this study was verified to follow a crystalline ordered arrangement, suggesting that its anisotropic mechanical properties were influenced by spatial hindrance and branching interactions. Changes in branching affected main chain orientation, crosslinking points, and spatial hindrance concurrently in the three-dimensional space. Specifically, E_x, E_z, and G₍₀₁₀₎ were impacted by branching and alterations in main chain orientation, and E_y, G₍₁₀₀₎, and G₍₀₀₁₎ were influenced by spatial hindrance.