In-situ 4D XµCT investigation of anatomy-dependent deformation and damage evolution in wood under radial compression

Transverse compression is critical for engineered wood applications, including bearing zones, structural connections, and compression-based densification treatments. However, conventional macroscopic testing cannot fully capture how different wood anatomical features mediate yield localization, lumen closure and damage evolution. In this study, in-situ 4D X-ray micro-computed tomography (XµCT) was used to investigate radial compression across eight anatomically diverse wood species up to 40% strain. The time-resolved datasets enabled direct observation of deformation from the elastic stage through initial yielding to densification within the same specimens. Initial yielding localized in regions of anatomical instability, including tracheid buckling in softwood and vessels collapse in hardwood. During post-yield compression, deformation pathways differed depending on anatomical organization and deformation compatibility. Species with coordinated cellular deformation show efficient lumen closure and density accumulation, whereas limited deformation compatibility between anatomical components leads to stress localization, structural disruption, and crack-driven strain dissipation. The findings provide direct in-situ evidence relevant to compressed wood, densified wood products and engineered timber design, and offer an experimental basis for future image-based modelling of compression-induced deformation.