Effect of shear deflection on vibrational properties of compressed wood

In this paper, we have investigated vibrational properties of compressed Japanese cedar (Cryptomeria japonica D. Don). The test specimens were compressed in the radial direction at 180degreesC for 5 h. Compression ratios (the ratio of deformation to the initial thickness) were 33% and 67%, and the vibrational properties were measured by free-free flexural vibration test. The contribution of shear deflection was large when the length-to-depth ratio was small and the Young's modulus to shear modulus ratio was large. The Young's to shear modulus ratio increased as the compression ratio increased and was larger under vibration in the radial than in the tangential direction. The loss tangent increased when the contribution of shear deflection to total measured flexural deflection increased.