Decoupling of factors influencing interface characteristics in basalt fiber-reinforced polymer composites

Intermolecular interactions, the relative contributions of interfacial factors, and their roles in strengthening fiber-reinforced composites remain insufficiently understood. Here, computational simulations are employed to perform decoupling analysis of chemical groups and surface morphology at basalt fiber(BF)-reinforced composite interfaces and to elucidate the regulatory effect of silane coupling agent on resin conformations. γ-aminopropyl triethoxysilane (KH550) balances highly positive and negative electrostatic regions on the BF surface, promoting multiple binding sites with resin molecules. At the BF/polyamide 66 (PA66) interface, KH550 modification increases the number of hydrogen bonds by 10.4% and makes the interfacial interaction energy more negative, from -384.4 to -487.9 kcal/mol. For BF-PA66, BF-epoxy resin (EP), and BF-polypropylene (PP) composites, interactions provided by KH550’s amino groups contribute more to interface mechanical enhancement than surface morphologies. At the BF/PA66 interface, amino-group introduction and atomic-scale morphology modification enhance the interfacial mechanical response by factors of 1.49 and 1.29, respectively. For BF-PA66 and BF-EP interface, atomic-level surface morphology regulating resin molecular chain arrangement conformations optimizes mechanical properties more effectively than surface asperities enabling resin infiltration. KH550 transforms resin molecular chains from surface-aligned conformations into interpenetrating structures due to enhanced interaction and steric hindrance effects. Atomic nanoindentation reveals that KH550 modification redirects resin deformation from interfacial sliding to bulk-matrix deformation, leading to a transition from adhesive to cohesive failure and increasing the maximum indentation force from approximately 2.9 to 4.0 nN. This research clarifies the intrinsic interfacial strengthening mechanism and provides guidance for rational interphase design.