High-resolution renders of wood tracheid (left). One-dimensional parametrization of wood rays (right)
Source: Sergio J. Sanabria et al.
From the cellulose fibrils to the cell wall and the arrangement of the early and late wood cells in a growth ring up to the beam by nature wood is an optimized high-performance material that fascinates and inspires craftsmen, architects, engineers, and scientists. In the digital age, beside standard laboratory experiments, models and simulations are increasingly utilized to better understand and predict the behaviour of the material exposed to various stress. For this purpose, numerical values of deformations at subcellular scale are required, which could now be obtained in experiments carried out at the TOMCAT beamline (TOmographic Microscopy and Coherent rAdiology ExperimenTs) of the SLS (Swiss Light Source): Wood samples made of spruce (Picea abies Karst.) with a test cross-section of at least 1 mm² were exposed to tensile or compressive stress. The structural changes at cell level were recorded using computer tomography. For post-analysis of the 3d microstructure of wood, an approach was developed that allows tracking individual cells detected within several tomograms of different load states. By doing so, the cell geometries and the subcellular deformation behaviour were quantified. Under tensile load, for example, the cell wall thickness narrows by around 0.8%, which is around 28 nm for the measured average cell wall thickness of 3.5 µm. These and other findings now provide a direct numerical linkage between deformations of the wooden microstructure and its resulting macroscopic behavior.
In‑situ quantification of microscopic contributions of individual cells to macroscopic wood deformation with synchrotron computed tomography
S. J. Sanabria, Franziska Baensch, M. Zauner, P. Niemz
published in Scientific Reports, Vol. 10, page 21615 et seq., 2020
BAM division Sensors, Measurement and Testing Methods