Mechanical properties and microstructure of Zabelia biflora
Zabelia biflora, a kind of broad-leaved shrub, with six distinct longitudinal furrows and petal-like structure in cross section, belongs to Zabelia and consists of sections interlaced with each other. It is meaningful to focus on the peculiar appearance of Zabelia biflora for the sake of outstanding structures. On the basis of quasi-static experiments of stretching, compression along the grain direction and bending in the tangential direction, dynamic experiments of the wood over its water contents ranging from 9% to 22% have been investigated using the split Hopkinson pressure bar. Combined with the electron scanning, 3D X-ray scanning reveals the microstructure of Zabelia biflora. Results show that the maximum bending force of this wood on the joint is higher than that of wood without the joint. Besides, although the static mechanical parameters of Zabelia biflora are basically the same order of magnitude compared with other hardwoods, the bending strength of the specimen with a joint is significantly improved by contrast with the wood possessing a similar density with it. In addition, it is been proved that there is a symmetrical and glass-like density distribution in the center of the wood. Meanwhile, the density presents a gradient-layer distribution from the up-down view. The dynamic compression strength of the wood will decrease when the water content ascends at every strain rate. When the strain rate is relatively low, the compression strength will rise abruptly with the descent of the moisture content below the fiber saturation point, otherwise, this enhancement will be slower. Moreover, the strain rate exerts a reinforcement effect on the compression strength. It is not until the strain rate exceeds 1000 s-1 that there will be a sudden drop in the stress after the first arrival of the compression strength. The influence of the moisture content on dynamic platform stress of material matters only under low strain rates. Once the moisture content is higher than the fiber saturation point, this effect will also disappear.