INFLUENCE OF MOISTURE SORPTION ON THE COMPRESSIVE PROPERTIES OF HARDWOODS

Samples of nine tropical hardwoods from Peru and sugar maple wood from Quebec were selected to undergo moisture sorption tests associated with either a parallel to grain compression test or a perpendicular to grain tangential compression test at 25 C. Results indicated that, for a given equilibrium moisture content, the transverse strength is lower after desorption than after adsorption. The magnitude of this phenomenon, called second-order effects of moisture sorption, varied with the species and with the mode of measurement of the strain. Hence, it seems that the distribution of deformation influences the second-order effects in tangential compression. Also, it was shown that second-order effects of moisture sorption associated with parallel to grain compression strength are explained by those related to the transverse swelling of wood. These effects are thereby proportionally greater in the perpendicular to grain direction of wood than in the parallel to grain direction.