Empirical Data for Modeling: Methodological Aspects in Experimentation Involving Hygromechanical Characteristics of Wood

Abstract

Realistic modeling of hygromechanical behavior of wood and wood-based composites undergoing moisture changes is an essential for optimization of drying processes as well as fordevelopment of design code provisions that account for long-term deformations in structures exposed to climate variations. Accurate prediction of such behavior requires not only mathematical models capable of describing multi-physics phenomena of transfer of heat and moisture, hygro-expansion, creep as well as thermo-mechanical and mechano-sorptive effects as they develop in time under changing external conditions, but also, clearly defined, meaningful, and reliable material data. Although numerous mathematical models and detailed theoretical descriptions have been proposed over time, the advance was not matched by development of adequate empirical procedures to determine the necessary material-level characteristics. It is clear that the experimental determination of basic hygromechanical characteristics of wood on a material level remains a serious challenge.

Progress in this area requires better understanding and cooperation between the communities of modelers and experimentalists. New quality may be achieved when development of advanced modeling techniques, which are better suited to deal with heterogeneous and anisotropic nature of wood and wood-based materials, is combined with experimental techniques utilizing advanced full-field imaging measurement techniques (e.g., optical techniques for measurement of deformations and stains based on digital image correlation; high-resolution x-ray tomography) and inverse problem methodology.

Keywords:

• Advanced/integrated testing protocols
• Digital image correlation (DIC)
• Empirical methods
• Finite element method (FEM)
• Full-field imaging techniques
• Material point method (MPM)
• Mechanical characteristics
• Modeling
• Wood
• Wood-based composites
• Computed tomography (CT)

ACKNOWLEDGEMENTS

This article summarizes some conclusions emerging from a project supported by the National Research Initiative of the USDA Cooperative State Research, Education and Extension Service, grant number 2001-35103-10048. The author also expresses special thanks to Dr. R. Lagana (Technical University of Zvolen, Slovakia), H.L. Frandsen (Ph.D. candidate from Alborg University, Denmark), Dr. S.M. Shaler (professor and associate director of the Advanced Engineered Wood Composites Center, University of Maine), and Dr. W. Davids (associate professor, University of Maine).