Synergistic Aramid Nanofiber/Graphene Oxide Interlocking Interface in PI/EPDM Composites: Regulation on Ablation Behavior

The primary material used for insulation layers in solid rocket motors is fiber-reinforced ethylene-propylene-diene monomer (EPDM) rubber-based composites. However, current research has primarily focused on the relationship between fiber/rigid resin matrix interfaces and macroscopic properties, while studies investigating the influence of fiber-flexible rubber matrix interfaces on composite macroscopic performance remain remarkably scarce. To deeply investigate the influence of the fiber-flexible rubber matrix interface on the macroscopic performance of composites, this study proposes a combined approach of coating and surface nanostructuring to construct a hybrid interfacial phase composed of graphene oxide (GO) and aramid nanofibers (ANF) between polyimide (PI) fibers and EPDM. Specifically, ANF stably binds with GO through π–π* interactions, forming a three-dimensional nanoscale surface structure that introduces nanolevel roughness. Low-field nuclear magnetic resonance (NMR) and ablation resistance analyses demonstrate that this structure facilitates the formation of a denser cross-linked network and a high-temperature-resistant architecture with uniformly dispersed GO on the fiber surface. As a result, the composite exhibits a 50% increase in tensile strength and an approximately 15% reduction in carbonization rate. This work demonstrates that optimizing the microinterfacial layer between fibers and the matrix not only enhances macroscopic mechanical properties but also achieves superior ablation resistance. The findings provide critical guidance for the development of high-performance EPDM-based insulation materials.