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Description
In this work, we provide the first assessment of the microstructure and mechanical properties of Malouetia Tamaquarina (Aubl.) (Apocynaceae), commonly known as Molongó wood. The timber grows in the Amazonian region in blackwater areas and is employed in arts and crafts by indigenous populations.
The microstructure was characterised via scanning electron microscopy (SEM), X-ray computed tomography (XCT), and mercury intrusion porosimetry (MIP). In particular, XCT scans were performed at two different resolutions (3.1 µm and 0.594 µm) to evaluate the cell wall thickness and pore size at different length scales. The wood exhibits a highly porous cellular structure, with porosity values reaching up to 87.8%, as measured through XCT and MIP. Rectangular cells are observed with walls ranging from 2.6 to 10 µm in thickness and pores diameter between 20 and 80 µm, exhibiting a similar morphology to that of softwood trees (shown in Figure 1). Additionally, pits are observed along the cell walls, which regulate water transport across the cells during the plant's cyclic flooding.
Mechanical testing was employed to assess the response in tensile, compressive, flexural, and Charpy impact loading. A strong anisotropy is observed, where the longitudinal direction exhibits the highest strength and stiffness due to the wood's cellular structure. Tensile and flexural moduli reach 0.85 GPa and 0.82 GPa, respectively. In contrast, the impact resistance is highest in the transverse direction due to the deformation of the pits. The lignin content of the wood is 27.1%, which is in line with that of lightweight angiosperm woods.
The results suggest that Molongó wood combines low density and favourable specific properties, indicating potential for lightweight, sustainable structures.
