Phthalonitrile Resin Composites Reinforced by Basalt and Carbon Fabrics: The Influence of Fiber Composition and Curing Temperature

Abstract

Hybrid fiber‐reinforced phthalonitrile composites are promising candidates for extreme‐environment applications, yet the coupling effects of ply configuration and curing temperature on the performance remain poorly understood. In this work, hybrid composite laminates were fabricated using phthalonitrile as the matrix, with basalt fiber (BF) and carbon fiber (CF) cloths as co‐reinforcements. The effects of inner CF ply number (1–4 layers) and final curing temperature (260°C–320°C) on the mechanical and thermal properties were systematically investigated. The results show that inserting 4 inner CF plies (6B4C specimen) delivers a peak flexural strength of 515 MPa, while CF cloth incorporation improves composite toughness by reducing flexural modulus and increasing maximum deflection. The 6B4C sample achieves a maximum T gtan (determined from tanδ peak) of 351.1°C with a char yield of 92.1% at 800°C. T gtan presents a monotonic upward trend with increasing curing temperature, reaching the highest value of 402.3°C after curing at 320°C, whereas excessive curing temperature induces matrix brittleness and micro‐defects, leading to notable mechanical property degradation. This work provides a clear process‐structure‐performance guideline for designing high‐performance phthalonitrile‐based hybrid composites for high‐temperature service scenarios.