Characterization of the dynamic and viscoelastic behavior of Pinus radiata wood impregnated with a bio-based organic phase change material (bio-PCM)

This study examines the impact of bio-based phase change material (bio-PCM) impregnation on the dynamic and viscoelastic properties of Pinus radiata wood. Specimens were impregnated with PlusICE Organic A26 through a controlled vacuum-pressure process, and their microstructure, dynamic properties, and time-dependent mechanical response were analyzed using X-ray micro-computed tomography, the Impulse Excitation Technique, and uniaxial stress relaxation tests fitted to a generalized Maxwell model. PCM impregnation resulted in a 24.7% reduction in volumetric porosity, an increase in the flexural complex modulus (E_flex^∗), and a decrease in the loss factor (tanδ), indicating a stiffer and less damped response in all anatomical directions. Moreover, stress-relaxation tests showed higher residual stress ratios (σ_∞/σ₀) in impregnated wood, indicating reduced viscoelastic relaxation capacity across different strain levels. These findings indicate that bio-PCM impregnation increased the stiffness and long-term stability of Pinus radiata while limiting energy dissipation. Such modifications provide a mechanical reliability assessment of PCM-impregnated Pinus radiata wood, which is required when phase change materials are incorporated into construction systems for thermal energy storage.