ABSTRACT Natural fiber‐reinforced weft‐knitted composites with superior formability and elastic recovery lack reliable mechanical stability under extreme temperatures, limiting industrial applications, and the synergistic regulatory mechanism between temperature and fiber mixing ratio remains unclear. To address this gap, this study innovatively develops a natural‐inorganic hybrid weft‐knitted structure and manufactures flax/basalt‐reinforced polylactic acid composites with tunable mixing ratios: Pure flax, pure basalt and flax/basalt ratios of 3:1, 2:1, 1:1. Systematic investigations of their mechanical evolution and fracture mechanism at 40°C to 50°C were conducted via tensile tests, flexural tests, dynamic mechanical analysis and three‐dimensional microscopic observation. All composites displayed distinct low‐temperature strengthening and high‐temperature degradation: The flax/basalt = 2:1 composite showed 75.6% and 36.8% higher flexural and tensile strength at 40°C than at 20°C, while these properties declined by 29.3% and 31.0% at 50°C. The flax/basalt = 1:1 ratio achieved optimal industrial balance, with 90.0% and 263.6% higher flexural and tensile stress than pure flax, reconciling high‐temperature toughness and low‐temperature brittleness. Temperature‐governed fracture mode transition: Fiber fracture dominated at low temperatures, matrix cracking prevailed at high temperatures, and basalt fibers inhibited catastrophic failure via bridging. Dynamic mechanical analysis confirmed fiber hybridization enhanced interfacial uniformity and temperature stability, reducing high‐temperature modulus loss. This study clarifies the temperature‐fiber mixing ratio synergistic mechanism, solves extreme‐temperature reliability issues, and recommends flax/basalt = 1:1 for balanced performance, 2:1 for low‐temperature scenarios, and pure basalt for high‐strength demands in automotive, cold‐region construction, and unmanned aerial vehicle applications, providing direct technical support for industrial material selection.
Han et al. (Fri,) studied this question.