压前含水率对杉木间伐材压缩木性能的影响

通过对杉木间伐材压缩密化的水分和物理力学性能进行分析,并观察木材微观结构的变化,可得出以下结果：1)压缩木各方向的水分分布不均匀,容易翘曲变形；2)水分对压缩木的物理力学性能有影响,压前含水率50％左右,压缩木硬度、抗弯弹性模量和抗弯强度最大,但冲击韧性随着压前含水率的增加呈下降趋势。从微观结构的观察可知,杉木间伐材压缩木的细胞只是被挤压,细胞腔变小而细胞壁未受到破坏。为了降低压后含水率,使水分分布均匀,可以采取两种办法：一是使初始含水率尽可能低,二是热压时间尽可能长。

Influence of Initial Moisture Content on Mechanical Properties of Compressed Chinese Fir Thinnings

Through analyzing the moisture distribution, physical and mechanical properties of compressed Chinese fir thinnings,following conclusions are drawn; 1) Moisture distribution in different directions (longitudinal, radial and tangentia) of the compressed wood is uneven,which leads to wrap and distortion;2) Initial moisture content (before compression) has influence on mechanical properties of the compressed wood: the hardness, MOE and MOR of the compressed wood with initial moisture content being about 50% are the best,but impact strength shows a tendency to drop with increase of initial moisture content. By observing microscopic structure of the compressed wood, it is found that only cell cavity of Chinese fir has been compressed, but cell wall has not been destroyed. In order to reduce moisture content of compressed wood and improve its moisture distribution, two methods can be adopted,one is to lower down initial moisture content of thinnings to be compressed,the other is to extend the hot press time.