落叶松和桦木木材切面的剖切方向对胶接性能的影响

Effects of Grain Orientation of Larch and Birch on Bonding Properties

研究了落叶松和桦木木材切面的剖切方向对胶接性能的影响 ,试验结果表明 :落叶松径切板的干状压缩剪切强度比弦切板的大 ,而湿状压缩剪切强度径切板的比弦切板的要小 ;而对于桦木 ,径切板的干状压缩剪切强度比弦切板的小 ,而湿状压缩剪切强度径切板的比弦切板的要大。文中还分析了造成这些现象的原因 ,造成落叶松径切板的干状压缩剪切强度比弦切板大的原因主要是落叶松木材早晚材间的差异大 ,造成落叶松径切板的湿状压缩剪切强度比弦切板小的原因主要是落叶松早晚材的湿涨率不一样以及有纹孔的作用 ;造成桦木径切板的干状压缩剪切强度比弦切板小的主要原因是弦切面是横断木射线 ,因此 ,在弦面上留下射线管胞的孔隙 ,在胶接时胶粘剂渗入就形成了更多的胶钉 ,而在湿状时这种孔隙成为了水分的通道 ,因而使而桦木湿状压缩剪切强度径切板的比弦切板的要大。

Effects of grain orientation of larch and birch on bonding properties were studied in this paper. The results show that quarter-sawn board of larch has greater dry compressing shear strength than flat-sawn board in normal conditions, Whileas quarter-sawn board of larch has smaller wet compressing shear strength than flat-sawn board for repeatedly boiling samples; quarter-sawn board of birch has smaller dry compressing shear strength than flat-sawn board of birch in normal conditions. Whileas quarter-sawn board of birch has greater wet compressing shear strength than flat-sawn board for repeatedly boiling samples. The reasons which cause those phenomena were also analysed in this paper. The main reason for which quarter-sawn board of larch has greater dry compressing shear strength than flat-sawn board of larch in normal conditions is great differences between springwood and summerwood of larch. The reasons for which quarter-sawn board of larch has smaller wet compressing shear strength than flat-sawn board of larch for repeatedly boiling samples are as follows: first of all, antiswelling efficiency between springwood and summerwood of larch is different; secondly, pits of larch have great effect on this aspect. The reasons for which quarter-sawn board of birch has smaller dry compressing shear strength than flat-sawn board of birch in normal conditions is that xylary rays in flat-sawn board are transversely cut and leave a lot of pore in the flat-sawn board, so, adhesive can enter these pore and turn into adhesive nail. While these pores provide a kind of tunnel for water, thereby cause this phenomenon that wet compressing shear strength of flat-sawn board of birch is smaller than that quarter-sawn board of birch.