Correlation of the interfacial properties and mechanical performance of hard-soft composites: A molecular dynamics perspective

Hard-soft composites combine the high strength of the hard phase with the flexibility and processability of the soft phase, showcasing significant application potential. Current researches on the mechanical performance of these materials primarily focuses on macro- and mesostructural influences, leaving the micro-level effects of interface properties unclear. In this work, ceramics (Al₂O₃ and Si₃N₄) were selected as the hard phase, while polymers (epoxy resin (ER), polymethyl methacrylate (PMMA), and polyethylene (PE)) served as the soft phase, resulting in a series of composites with varying interface properties. Molecular dynamics simulations were employed to investigate the mechanisms by which interface properties affect mechanical performance. The results indicate that the presence of polymer coatings significantly enhances mechanical performance, particularly during compression. Among all combinations, the Al₂O₃-PMMA system exhibited the best performance, attributed to the strong electrostatic attraction between the two phases, which enables the ceramic phase to withstand greater stress during tensile or compressive loading. Additionally, when the ceramic phase undergoes bending, significant van der Waals repulsive forces develop, preventing further bending and improving damage tolerance. The results enhance the understanding of the micro-mechanisms through which interface properties affect mechanical performance, facilitating the design of promising hard-soft composite materials.