Strain Rate Triggered Network Locking in Shear‐Stiffening Gel/Wood Fibres Composites for Adaptive Impact Protection

ABSTRACT Lightweight structural materials capable of simultaneously sustaining mechanical load‐bearing and dissipating extreme impact energy remain a long‐standing challenge, as conventional systems are constrained by the intrinsic trade‐off between stiffness and toughness under dynamic loading. In this work, we address this limitation by introducing a strain rate triggered network locking strategy that enables adaptive mechanical reconfiguration in poplar fibres (PFs) and shear stiffening gel (SSG) composites (PSCs). PSCs are constructed by integrating PFs networks with SSG, forming a hierarchical interpenetrating architecture in which interfacial interactions and dynamic bonding jointly govern the mechanical response. Under low strain rate loading, PSCs enabled efficient stress distribution, achieving a flexural strength of 58.88 MPa with a balanced toughness. Under high strain rate loading, PSCs reached an energy absorption per unit thickness of 2.04 J·mm −1 and a force per unit thickness of 377.80 N·mm −1 . Notably, a steel projectile impacting at 153.4 m·s −1 rebounded, further demonstrating its potential as a scalable biobased adaptive impact‐resistant panel. This strain‐rate adaptive design principle provides a general pathway for structural materials, enabling them to simultaneously achieve static load‐bearing capacity and dynamic impact protection, and offers a scalable route for the development of biobased adaptive impact‐resistant panels.