Biomaterials heterogeneous displacement, strain and swelling under hydric sorption/desorption: 2D image correlation on spruce wood

Abstract

Spruce wood, as all biosourced materials, is very sensitive to relative humidity changes, which can cause dimensional variations. In some cases, it leads to eccentricity, degradation and deterioration of the wooden structures. The 3D methods of evaluation of the spruce wood hydric behavior needs important financial resources and investigation. That’s why, the main objective of this study is to develop the technics of 2D digital image correlation to estimate the local displacements and strains values under hydric solicitations and to follow the hysteresis phenomenon, anisotropy and swelling coefficient. In this context, cycles of sorption - desorption for relative humidity that vary from 0 to 100% were applied. Results represent swelling coefficients for early- and latewood as a function of wood directions. A particular attention was devoted to the uncertainty of the 2D digital image correlation technics for both earlywood and latewood. This study provides the literature and future research with promising results especially concerning the evolution of the microscopic morphology of biosourced materials when exposed to relative humidity variations, which can significantly affect their macroscopic behavior.