Viscoelastic properties of hardwood from the Congo Basin

Abstract

This study explores the viscoelastic behaviour of six tropical hardwood species from the Congo Basin: Azobé, Okan, Padouk, Sapelli, Fraké and Ayous, through dynamic mechanical analysis. These woods, commonly used in structural, furniture and outdoor applications, are subjected to thermal and mechanical stresses that significantly influence their long-term performance. Tests were carried out under controlled temperature and frequency conditions to evaluate the evolution of three key parameters: storage modulus (E′), loss modulus (E″) and loss factor (tan δ). Results reveal that the mechanical response of these materials is strongly dependent on temperature, frequency and wood density. Dense species such as Azobé and Okan exhibit higher stiffness and thermal stability, while lighter species like Fraké and Ayous show greater sensitivity to thermal softening and energy dissipation. The microstructural differences between species, such as cell wall thickness and porosity, are found to directly influence their viscoelastic properties. These findings highlight the need to consider both anatomical structure and operating conditions when selecting wood for applications exposed to varying thermal environments.