ANISOTROPY IN THE THERMAL EXPANSION AND COMPRESSION STRENGTH OF THREE WOOD SPECIES FROM PLANTATIONS

Abstract

The objective of this study was to evaluate the anisotropy on dimensional changes and the compression behavior of three wood species from commercial plantations (Eucalyptus nitens, Tectona grandis and Gmelina arborea) generated by a thermal treatment. To accomplish the goal, dilatometric tests and compression tests were performed in the three main directions of wood: tangential, radial and longitudinal. It was found a high anisotropy on coefficients of linear thermal expansion (CTE) and on compression tests for the three main directions considered of the wood. The values in the longitudinal direction were close to zero. The values in the tangential direction were higher than in the radial direction. In terms of mechanical resistance, the longitudinal direction showed the highest strength. The radial strength was slightly higher than the tangential. Thermal treatment increased the strength to compression and the resistance to deformation in the elastic region. The modulus of elasticity increased up to 30.9%, the stress at proportional limit up to 27.3% and the modulus of rupture up to 30.3%, in the longitudinal direction. It was found that thermal treatment had a higher effect on the mechanical properties of lower density wood. Contrary, the mass loss increased for this wood, finding values around twice than those obtained for the denser wood.