Mechanical behavior and ductile-brittle transition in structural wood: Experimental characterization and predictive modeling for cold-climate applications

Wood, as a natural engineering material, exhibits increased susceptibility to brittle fracture in humid-cold environments. Current research lacks comprehensive understanding of the mechanical behavior and ductile-brittle transition (DBT) characteristics of wood during elastic-plastic deformation across a broad sub-zero temperature range. This study systematically investigated the temperature-dependent mechanical properties of poplar (Populus ussuriensis) and larch (Larix gmelinii) wood in three moisture states (oven-dry, fiber-saturation-point, and water-saturated) from −196 °C to 20 °C. Three-point bending tests and fractographic analysis were conducted to quantify the temperature-dependent evolution of MOE, MOR, ductility, and brittleness. The results revealed that decreasing temperature led to increased MOE, MOR, and brittleness, accompanied by significant ductility reduction. A distinct ductile-to-brittle transition was identified at approximately −40 °C, serving as a critical temperature threshold for fracture mode transformation. Nonlinear surface-fitting models were developed to describe the relationships between mechanical properties and temperature/moisture content, demonstrating excellent predictive capability (R2 = 0.84–0.99). Furthermore, an empirical power-law model (R2 ≥ 0.94) was established between ductility and brittleness, providing a quantitative framework for assessing brittle fracture probability through ductility changes. These findings offer fundamental insights into the temperature-dependent mechanical behavior and fracture characteristics of wood in cold environments, providing scientific guidance for failure risk assessment and structural design of wooden components in frigid regions.