The Effect of Moisture Content and Temperature on Mechanical Properties of Clear Wood Samples Cut from Southern-Pine Lumber

Abstract

Southern yellow pine is a softwood species group abundantly found in the Southeast United States. With the increasing trend towards promoting sustainable construction, mass timber members such as cross-laminated timber and glulam members made from southern pine wood are becoming more widely used. Despite the widespread use of southern pine wood in construction, there are limited studies investigating the fundamental mechanical properties (strength and stiffness) of southern pine wood at the material level under different environmental conditions. This thesis presents a research study focused on characterizing generic southern yellow pine by testing clear wood samples under various load and sample conditions according to ASTM D143-22 (2022), with slight deviations when necessary. The objective was to experimentally evaluate the effects of temperature and moisture content on the wood’s mechanical properties.

The loading conditions included compression both parallel and perpendicular to the grain, bending, shear parallel to the grain, and tension both parallel and perpendicular to the grain. The sample conditioning groups encompassed five temperature and moisture content combinations, with three temperature conditions (-22°F, 70°F, and 150°F) and three moisture content levels (4%, 12%, and 25%). The sample conditioning combinations were designed to vary a single parameter between the conditioning groups to clearly observe the effects on strength and stiffness properties. The test results were mostly consistent with prior studies indicating that mechanical properties mostly decreased at high moisture content and increased at low moisture content. The impact of temperature on high-temperature properties was more marginal. Overall, the study contributes valuable insights into the behavior of southern yellow pine under different environmental conditions.