Differences in dry shrinkage of bamboo rings with multiple heights and radians based on vascular bundle group

Abstract Moso bamboo is widely used in production due to its high strength-to-weight ratio, fast growth and renewability. Meanwhile, bamboo’s dimension is highly sensitive to moisture, resulting in cracking and other defects easily. This study aimed to investigate the changes in cracks, bamboo ring shapes, fiber sheath area and volume fraction, and vascular bundle group shapes from the green state to the absolute-dry state, using the target detection model and Python fitting technique. The results showed that the radius of the vascular bundle group increased while its radian and arc length decreased with a decrease in the moisture content. The decrease in the cross-sectional area was greater than that in the wall thickness and arc length. The dry shrinkage of the fibers was greater than that of the rest tissues, which was an important part of the shrinkage of bamboo rings. Obvious cracks mainly appeared in the bamboo ring with a complete radian of 2π, while almost no or very limited cracks were seen in other rings with incomplete radians. This study further elaborated on the dry shrinkage changes and differences in bamboo rings, which might be beneficial to restrain the deformation and cracking of bamboo products effectively.