Using modeling to understand the hygromechanical and hysteretic behavior of the S2 cell wall layer of wood

Abstract

To understand moisture sorption and swelling of wood requires reveal- ing the behavior at the S2 cell wall layer, one of the layers of the secondary cell wall, at the atomistic scale. Difficulties in experimentally determining the organi- zation and properties of S2 layer at such a small scale are a stumbling block for understanding of swelling and sorption in their full complexity. Recent works using atomistic modeling (Molecular Dynamics (MD) and Grand Canonical Monte Carlo) provide complementary insights. The linear dependence between moisture content, swelling, and porosity change is found to be correlated with the number and location of water-polymer hydrogen bonds within the system. Such information is upscaled for general use within a poromechanical framework. This chapter summarizes recent new physical insights in the sorption and swelling behavior of the S2 cell wall layer, stemming from validated MD work. The presented methodology is also used to unravel other moisture-related mechanisms of wood, such as hysteretic behavior.