MECHANO-SORPTIVE BEHAVIOUR OF <em>EUCALYPTUS</em> <em>PELLITA</em> DURING INTERMITTENT AND CONTINUOUS DRYING

Abstract

Intermittent drying can reduce collapse shrinkage rate and decrease internal checks within certain timbers. This study was aimed at investigating and comparing mechano-sorptive behaviour, which explained the stress/strain formation of Eucalyptus pellita during intermittent and continuous drying regimes. The study applied 50 °C for the heating phase of one continuous and two intermittent regimes. One intermittent regime had its temperature raised to 55 °C when the samples reached below fibre saturation point. The study showed that the intermittent regimes reduced shrinkage strains in E. pellita by 0.004–0.031. The instantaneous strain in the surface of E. pellita boards exposed to intermittent regime was 0.001–0.007 smaller than those in the continuously dried boards. Nevertheless, the selected regimes caused viscoelastic and mechano-sorptive strains as large as or much larger than those in the continuous regime. Compressive stress was a dominant stress causing the shrinkage strain formation in E. pellita boards exposed to both drying regimes. Other strains were affected by the combination of compressive and tensile stress developed in the middle and/or surface of the boards. Statistical tests confirmed the significant effect of the drying technique applied, not the provenance factor, on mechano-sorptive behaviour of E. pellita.