Multiscale mechanisms of water-induced hemp fiber reinforcement

Abstract

Abstract Natural cellulosic fibers such as hemp are increasingly important for sustainable textiles, biocomposites, and eco-friendly structural materials, where mechanical performance is governed largely by how water is managed during processing; understanding water-induced reinforcement of these fibers is, therefore, essential for the reliable manufacture of high-performance, low-carbon fiber-based products. This work presents a multiscale investigation into how water governs the transition from a hydrated state to a fully dried structure and, in doing so, enhances hemp fiber interactions after wetting. In the wet state, COMSOL multiphysics simulations show that microscopic water bridges generate capillary forces that draw neighboring hydrophilic fibers together and initiate structural densification. As drying progresses and water gradually evaporates, molecular dynamics simulations reveal that the remaining adsorbed water reorganizes into a hydrogen-bond network that reinforces the contacts between cellulose chains. Experimental tensile tests conducted under controlled humidity conditions further demonstrate that hemp inter-fiber cohesion changes systematically with moisture content and reaches a maximum when capillary compaction and hydrogen-bond formation both contribute to cohesion. These findings clarify how water, during its removal from the material, sequentially enables capillary-driven packing and molecular-level bonding. The combined insight provides a mechanistic basis for cellulosic fiber processing and application.