Displacement Fields of Wood in Tension Based on Image Processing: Part 1. Tension Parallel- and Perpendicular- to-Grain and Comparisons with Isotropic Behaviour

Displacement fields for tensile loaded rubber and wood in paralleland perpendicularto-grain were obtained from digital image correlation. The results showed that the digital image correlation can reveal fine details of the nature of displacements in both rubber and wood. It was found that when load is perpendicular-to-grain, the lignin matrix produces uniform displacement fields similar to that of isotropic rubber. Uniform displacement fields also observed when lignin is involved in contraction due to Poisson effect in parallel-to-grain tension. However, when tracheids carry the load in parallel-tograin loading, or are compressed in perpendicular-to-grain loading, a complex displacement pattern distorted by internal shear stress and slippage is produced.