Hygromechanical mechanisms of wood cell wall revealed by molecular modeling and mixture rule analysis

Chi Zhang (1) , Mingyang Chen (1) , Sinan Keten (2) , Benoit Coasne (3) , Dominique Derome (4) , Jan Carmeliet (1)

1 ETH Zürich - Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich]
2 Northwestern University [Evanston]
3 LIPhy - Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères]
4 UdeS - Université de Sherbrooke

Despite the thousands of years of wood utilization, the mechanisms of wood hygromechanics remain barely elucidated, owing to the nanoscopic system size and highly coupled physics. This study uses molecular dynamics simulations to systematically characterize wood polymers, their mixtures, interface, and composites, yielding an unprecedented micromechanical dataset including swelling, mechanical weakening, and hydrogen bonding, over the full hydration range. The rich data reveal the mechanism of wood cell wall hygromechanics: Cellulose fiber dominates the mechanics of cell wall along the longitudinal direction. Hemicellulose glues lignin and cellulose fiber together defining the cell wall mechanics along the transverse direction, and water severely disturbs the hemicellulose-related hydrogen bonds. In contrast, lignin is rather hydration independent and serves mainly as a space filler. The moisture-induced highly anisotropic swelling and weakening of wood cell wall is governed by the interplay of cellulose reinforcement, mechanical degradation of matrix, and fiber-matrix interface.

Domaines: Matière Condensée [cond-mat]; Matériaux

Chi Zhang, Mingyang Chen, Sinan Keten, Benoit Coasne, Dominique Derome, et al.. Hygromechanical mechanisms of wood cell wall revealed by molecular modeling and mixture rule analysis. Science Advances , 2021, 7 (37), ⟨10.1126/sciadv.abi8919⟩. ⟨hal-03357587⟩