Effects of wet-dry cycling on the mechanical properties of Arundo donax L. used for the vibrating reed in woodwind instruments

摘要

The effects of wet-dry and moist-dry cycling on the mechanical properties of reed (Arundo donax L.) were investigated. Because water-soluble extractives were lost through wetting, the reed shrunk in its tangential direction, and its dynamic Young's modulus and loss tangent decreased during wet-dry cycling. On the other hand, the reed swelled in its radial direction because of the recovery of cell collapse, which had been induced by drying from a green state. Consequently, the resonant frequency of the reed monotonically increased during wet-dry cycling, whereas no clear trend was seen in bending rigidity. During moist-dry cycling, the equilibrium moisture content of reed decreased slightly. Such a reduction in hygroscopicity was attributed to the aggregation of deliquescent extractives. The changes in the dimensions and vibrational properties of the reed specimens during moist-dry cycling were qualitatively similar to those during wet-dry cycling. These results suggest that the practical performance of woodwind reed changes irreversibly during continuous usage.