Bidirectional Synergistic Strategy for Interface Enhancement of Basalt Fiber/Poly(ether sulfone) Composites via Waterborne Interlayer Construction and Matrix Reinforcement

Basalt fiber-reinforced poly(ether sulfone) (BF/PES) composites possess high strength and excellent thermal stability, yet their interfacial adhesion is poor due to the inert fiber surface and modulus mismatch. Thus, a bidirectional modification strategy was developed to simultaneously engineer the fiber surface and reinforce the matrix. A waterborne polyethylenimine (PEI)/graphene oxide (GO)/sulfonated poly(ether sulfone) (SPES) interlayer was constructed on BF via electrostatic layer-by-layer assembly, while carboxylated carbon nanotubes (OCNTs) were incorporated into the PES matrix. The PEI/GO/SPES interlayer introduced abundant polar groups and increased fiber surface roughness, thereby improving fiber wettability and interfacial stress transfer. Meanwhile, the OCNT-reinforced PES matrix enhanced the stiffness and load-bearing capacity of the composites. The resulting BF-P-G-S/PES@OCNTs composites achieved an interlaminar shear strength of 78.8 MPa, flexural strength of 423.5 MPa, and flexural modulus of 20.1 GPa, corresponding to improvements of 113.5%, 73.7%, and 191.3% over unmodified BF/PES. This enhancement was attributed to the synergistic effects of polar interactions, mechanical interlocking, matrix reinforcement, and continuous interfacial stress transfer. The study provides an environmentally friendly and efficient strategy for designing high-performance fiber/thermoplastic composites with strong interfacial adhesion and optimized load transfer.