Wood Material Behavior During Drying: Moisture-Dependent Tensile Stiffness and Strength of Radiata Pine at 70–150°C

Abstract

Improvements in kiln-drying efficiency and dried timber product quality are difficult to realize given the current lack of knowledge as to how in-kiln conditions impact wood basic properties such as strength and stiffness. In the last decade at Scion, significant effort has been invested in an initiative to evaluate the instantaneous stress-strain, time-dependent creep, and mechanosorptive behavior of radiata pine. The strength and stiffness of longitudinal specimens of radiata pine wood from the inner and outer portions of the stem have been evaluated across a range of low to high moisture contents at temperatures from 70 to 150°C. Results show expected decreases in both yield stress and MOE with increasing temperature and increasing moisture. Inner-wood is generally less rigid and strong than outer-wood. This article will review methodology and experimental results in addition to discussing trends in MOE and yield strength with temperature, moisture content, and sample type.

Keywords:

• Drying stress
• High-temperature drying
• Viscoelasticity

ACKNOWLEDGMENTS

This work has been financially supported by the Australian Forest and Wood Products Research and Development Corporation (FWPA) and by the New Zealand government through the Foundation for Research Science and Technology. The efforts of Scion staff, namely Hamish Pearson, Ian McElroy, and Steve Riley, have been essential in developing the novel material testing equipment and protocols employed herein.

Notes

^a Nominal moisture content.

^a Nominal moisture content.

^a Nominal moisture content.