Effect of shear deflection on bending properties of compressed wood

We investigated the bending properties of compressed Japanese cedar ( Cryptomeria japonica D. Don). The specimens were compressed in the radial direction under 180°C for 5 h. Compression ratios (the ratio of deformation to the initial thickness) were 33% and 67%. Young's modulus was measured by flexural vibration test and static bending test. As a result, the Young's modulus obtained by loading in the radial (R) and tangential (T) directions approached the value without shear influence as the length-to-depth ratio and the span-to-depth ratio increased. In the same compression ratio, the Young's modulus was closer to the value without shear influence in loading in the T-direction than in the R-direction. This is because the Young's modulus to shear modulus ratio of the tangential section was smaller than that of the radial section. In the static bending test, the Young's modulus at the span-to-depth ratio of 14 used in major standards was not appropriate.