A measurement framework for quantifying thermally induced combustion-front progression in wood using time-resolved X-ray computed tomography

Abstract

Non-destructive quantification of the internal progression of thermally induced degradation in wood using X-ray imaging is challenging because the material is inherently heterogeneous and the resulting intensity changes are small, spatially variable, and influenced by acquisition noise and partial-volume effects. A measurement framework was developed for quantifying combustion-front penetration in wood using time-resolved X-ray computed tomography (CT) during controlled one-sided heating. The focus was on defining and measuring the combustion front in CT data rather than detailed physical interpretation of underlying material transformations. A CT-compatible heating arrangement enabled repeated volumetric scanning without interrupting thermal exposure. An automated voxel-wise analysis pipeline was implemented, including baseline normalisation using robust median-based statistics, formation of depth-dependent profiles along the heating direction, and threshold-based front detection with sub-voxel interpolation. Measurements were evaluated within a fixed three-dimensional region of interest located approximately 10 mm inside the specimen boundaries to reduce edge effects and ensure reproducible spatial sampling. Validation against post-exposure visual assessment showed reliable front detection only when a statistically coherent volumetric signature was present. Application to a dynamic experiment enabled extraction of a representative propagation rate of 0.92 mm min ⁻¹ .