Measuring the Damping Performance of Gradient-Structured Bamboo Using the Resonance Method

Abstract

Bamboo has natural damping properties, but, due to the obvious gradient differences in bamboo walls, the damping properties of different layers may vary. Using bamboo slivers as the research object, this study investigated the underlying mechanism of the effect of microstructural and chemical components on the damping properties (η, damping ratio) of bamboo using the resonance and nonresonance methods. The damping ratio decreased on L3 (inner layer), L2 (middle layer), and L1 (outer layer) due to lower microfibril angles, increased crystallinity of cellulose, and decreased hemicellulose content. All of these limited the motion of the bamboo’s molecular chains. The damping ratio successively increased in the oven-dried, air-dried, and water saturated states because water acted as a plasticizer. The damping ratio of L1, in the oven-dried state, was slightly higher than that of the air-dried state because L1 had the lowest water content. This allowed less water to escape during drying, which intensified the molecular distortion. The initial tan δ (tangent of the loss angle) decreased successively on the L3, L2, and L1 layers of the bamboo, and the tan δ of L3 was lower than that of L2 due to changes in the temperature sensitivity of hemicellulose.