EFFECT OF THERMO-HYGROMECHANICAL BEHAVIOUR AT MACROSCALE OF WOOD UNDER COMPRESSION PERPENDICULAR TO THE GRAIN IN NANOMECHANICAL PROPERTIES OF CELLULAR STRUCTURE

Daniela Sepúlveda, Cecilia Bustos, William Gacitúa, Peter Dechent, Alain Cloutier

Abstract


The objective of this study was to evaluate and correlate at macroscale the thermo-hygromechanicaleffect of on the nanomechanical properties of Pinus radiata D. Don and Eucalyptus nitens(Deane& Maiden)evaluated in the S2 layer of the cell wall and in the middle lamella of specimens undercompression perpendicular to grain and under cyclic environmental conditions. At macroscale, 4 stresslaminateddeck specimens without preservative treatment were studied for both species and 4 deckspecimens of radiata pine treated with creosote. The nanomechanical properties of the cellular structurewere determined using nanoindentations. The results showed that the thermo-hygromechanical effectat macroscale induced a significant increase of elastic modulus and hardness of the cellular structureduring the summer season and during the second environmental cycle, with respect to the winter season and the first cycle. On the other hand, it was shown that the application of long-term compressive loadslead to a significant decrease of the elastic modulus and hardness of the cellular structure of wood andan increase in the relaxation factor, compared to the pieces submitted to free deformation.

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