In-situ quantification of microscopic contributions of individual cells to macroscopic wood deformation with synchrotron computed tomography

Abstract

Wood-based composites hold the promise of sustainable construction. Understanding the influence on wood cellular microstructure in the macroscopic mechanical behavior is key for engineering high-performance composites. In this work, we report a novel Individual Cell Tracking (ICT) approach for in-situ quantification of nanometer-scale deformations of individual wood cells during mechanical loading of macroscopic millimeter-scale wood samples. Softwood samples containing > 104 cells were subjected to controlled radial tensile and longitudinal compressive load in a synchrotron radiation micro-computed tomography (SRµCT) setup. Tracheid and wood ray cells were automatically segmented, and their geometric variations were tracked during load. Finally, interactions between microstructure deformations (lumen geometry, cell wall thickness), cellular arrangement (annual growth rings, anisotropy, wood ray presence) with the macroscopic deformation response were investigated. The results provide cellular insight into macroscopic relations, such as anisotropic Poisson effects, and allow direct observation of previously suspected wood ray reinforcing effects. The method is also appropriate for investigation of non-linear deformation effects, such as buckling and deformation recovery after failure, and gives insight into less studied aspects, such as changes in lumen diameter and cell wall thickness during uniaxial load. ICT provides an experimental tool for direct validation of hierarchical mechanical models on real biological composites.

Using In Situ Synchrotron‐Radiation‐Based Microtomography to Investigate 3D Structure‐Dependent Material Properties of Tension Wood

“…[23][24][25] More recent studies on softwood have demonstrated the disintegration of the wood structure under load (compression load). [26,27] Experiments performed with the load frame at the IBL should be considered exploratory, and consequently, the number of samples evaluated was comparably small. Nevertheless, our results show how high-resolution imaging of load sequences and the subsequent localization of strain can be applied to reveal functional relationships with sample morphology.…”

“…[ 23–25 ] More recent studies on softwood have demonstrated the disintegration of the wood structure under load (compression load). [ 26,27 ]…”

Bamboo’s tissue structure facilitates large bending deflections

“…In situ micro-CT studies are very powerful for investigating the local deformation behavior of tissues and cells upon external loading of bulk samples. To study wood structure and mechanics, sophisticated testing devices were built and cell deformations were studied with high resolution [30][31][32][33]. Figure 6 shows micro-CT images of bamboo slivers loaded in a simple testing setup, which were analyzed at the three different levels of span length reduction to measure the area change of PCs during the bending deflection.…”

A macroscopic Washburn approach of liquid imbibition in wood derived from X-ray tomography observations

“…For the same reason, water uptake occurs preferentially only in latewood in the case of heartwood 48 . Synchrotron facilities, which are capable of combining very high resolution with short acquisition times, have been successfully applied to the study of lignocellulosic products 58 – 60 .…”