Deformation under a repetition of moisturizing and drying of bamboo subjected to a set in bending

Abstract

The aim of this study was to elucidate the mechanisms of deformation change of bamboo set during bending with repeated moisturizing and drying. Deformation was represented by the set ratio, denned as the camber height normalized by the initial value of the fixed set. Susceptibility to deformation from moisture changes was estimated by the slope of the plot of the set ratio versus the moisture content. The set ratio decreased gradually during the repetition of moisturizing and drying, a property consistent with general wood materials. When the specimens were previously extracted in hot water, the set ratio increased but the slope did not change. On the other hand, a previous thermal treatment at more than 230°C or a set at less than 60°C affected both the set ratio and the slope: The set ratio decreased, and the slope increased. It is known that at 60°C hemicellulose starts to soften and at 230°C thermal degradation occurs. Thus, hemicellulose may play a role in the deformation properties of bamboo set during bending.