The radial differences in the tangential free shrinkage of Moso bamboo

In order to explore the causes of severe cracking, high drying stress in the drying process of bamboo, the characteristics of free drying shrinkage of bamboo (Phyllostachys edulis) were studied. The drying shrinkage behaviors of the intact and layered specimens were compared under drying conditions at 45°C. The key results are as follows: The drying rate of layered specimens was higher than that of intact specimens. Above fiber saturation point (FSP, MC ≥ 25%), the MC of the layered and intact specimens showed a gradient distribution, the MC gradient decreased with the decrease in MC. Below FSP (MC < 25%), the free drying shrinkage of the layered specimens decreased from T1 (bamboo outer skin) layer to T5 (bamboo inner skin) layer. The drying shrinkage coefficient (K) of the intact specimen (16%) was lower than that of the layered specimen (21%), and the maximum dry shrinkage (ymax) of the intact specimen (2.9%) was lower than that of the layered specimen (4.0%). The K and ymax of the layered specimens decreased from T1 to T5 layer, and the overall degree of decline continued to decrease. The FSP of the T5 layer is significantly greater than that of the other layers.