PHYSICO-MATHEMATICAL MODEL OF WOOD DURABILITY UNDER CYCLIC ENVIRONMENTAL CHANGES IN TEMPERATURE AND HUMIDITY

Introduction. A significant drawback of composite materials is their tendency to degrade over time, eventually leading to complete failure. Purpose of the study. The objective of this research is to identify the physical principles and develop a theoretical framework to explain this degradation. Wood, as a natural composite, serves as a convenient object for such investigations. Many physical and theoretical aspects of its behavior remain insufficiently understood. In particular, the reduction in mechanical strength at the junctions (with nagels) of wooden components under cyclic variations in temperature and humidity requires further exploration. Methods. This paper presents a physico-mathematical model for assessing the mechanical strength of wood under such environmental influences. The model is based on the Arrhenius equation and current understanding of wood’s cellular structure, whose key components are cellulose filaments (serving as the reinforcing framework) and lignin (the binding matrix). The model assumes that non-steady processes of heat and moisture transfer within the wood, driven by environmental conditions, gradually break the interatomic bonds within lignin compounds. Results. The study derives expressions to estimate the maximum number of wetting-drying cycles that wood can withstand, considering the material’s temperature. It also provides an evaluation of its service life (resource) affected by these cyclic influences. The proposed theory is of universal relevance.