A Closed‐Loop Recyclable Biocomposite Integrating Thermally Reversible Networks With Wood Fibers for High‐Performance Structural Applications

ABSTRACT Natural fiber‐reinforced thermoplastics face a critical trade‐off between reprocessability and dimensional stability. Here, we design covalent adaptable networks (CANs) synergizing wood fiber (WF) with dynamic transesterification chemistry to bridge this gap. The thermally reversible cross‐linked biocomposite (TRC‐bioC) was fabricated via hot‐press molding of WF (50–90 wt.%), E‐51 epoxy, and phthalic anhydride. The composite with 70 wt.% WF achieved synchronized mechanical superiority: 94.4 MPa flexural, 59.2 MPa tensile, and 8.7 kJ m ⁻² impact strengths, surpassing conventional WF/HDPE composites by 430%, 344%, and 271%, respectively. Simultaneously, it exhibited extraordinary dimensional stability with ultralow creep strain (0.048%), thickness swelling (0.47%), and thermal expansion (1.30 × 10 ⁻⁵ °C ⁻¹ ). These improvements originate from covalent cross‐linking, high glass transition temperature, and enhanced WF/epoxy interfacial bonding. WF doubled as a transesterification catalyst, allowing full component recovery and more than three reprocessing cycles. Combining industrial‐scale processability, aerospace‐grade stability, and closed‐loop recyclability, TRC‐bioC is a breakthrough for structural applications in aerospace and marine engineering.