Enhanced Mechanical and Thermal‐Mechanical Stability of Phthalonitrile/Basalt Fiber Composites via Multi‐Dimensional Interface Design

It remains a significant challenge in basalt fiber (BF) composites to achieve both high mechanical and thermal‐oxidative mechanical performance. This study proposes a method to construct multi‐dimensional interfaces through synergistic modification of BF and matrix reinforcement of phthalonitrile (PN) with carbon nanotubes. The BF/PN composite with a multi‐dimensional interface exhibited a 96.4% increase in flexural strength and a 109.5% increase in interlaminar shear strength (ILSS). After aging at 250°C for 90 h, the BF/PN composite with a multi‐dimensional interface achieved flexural strength and ILSS values of 1248.9 MPa (retention rate 95.4%) and 64.4 MPa (retention rate 94.6%), respectively, which are 97.8% and 107.1% higher than the pristine sample. The construction of multi‐dimensional interfaces led to tighter interfacial bonding, enhanced interfacial interactions, and improved stress transfer, thereby increasing the ability of the BF/PN composite to resist interfacial failure. This work provides a promising strategy for enhancing the overall performance of BF composites.