Mechanics of balsa (Ochroma pyramidale) wood

Balsa wood is one of the preferred core materials in structural sandwich panels, in applications ranging from wind turbine blades to boats and aircraft. Here, we investigate the mechanical behavior of balsa as a function of density, which varies from roughly 60 to 380 kg/m3. In axial compression, bending, and torsion, the elastic modulus and strength increase linearly with density while in radial compression, the modulus and strength vary nonlinearly. Models relating the mechanical properties to the cellular structure and to the density, based on deformation and failure mechanisms, are described. Finally, wood cell-wall properties are determined by extrapolating the mechanical data for balsa, and are compared with the reduced modulus and hardness of the cell wall measured by nanoindentation