Investigation on Fructure Phenomena of Large Wood Construction Menber using a Measurment Technique of Crack-Propagation

研究了粘接线对复合木材弯曲疲劳裂纹扩展的影响。胶粘剂有间苯二酚树脂胶粘剂和聚合物异氰酸酯水性胶粘剂。样品取自直径约90 cm的Agathis原木。对试样施加了完全相反的弯矩。应力循环的频率为每秒30次。所得结果如下：(1)有粘结线的试件在裂纹扩展曲线第二阶段（稳定阶段）区域影响较大。在第二阶段，最大的影响出现在约20%的试样宽度。(2)两条粘接线比一条粘接线的失效循环次数要多得多。(3)得到了裂纹扩展线跨越粘接线的状态。(4)水性聚合物异氰酸酯胶粘剂与间苯二酚树脂胶粘剂的循环失效次数基本相同。

The effect of adhesive line on the bending fatigue crack-propagation for laminated wood was investigated. Kinds of adhesive were Resorcinol resin adhesive and Aqueous Polymer isocyanate adhesive. Specimen were prepared from Agathis log about 90 cm in diameter. A completely reversed bending moment was applied to the specimen. The frequency of the stress cycles was 30 cycles per second. The results obtained are as follows.(1)Specimens having the adhesive line show the large effect in the region of the second stage (the stable stage) of the crack-propagation curve. In the second stage, the maximum effect appears on about 20 % of the specimen width.(2)Two adhesive line shows much more in number of cycles to failure than one adhesive line.(3)The state of the crack-propagation line across adhesive lines is appear.(4)Aqueous polymer isocyanate adhesive shows much the same as Resorcinol resin adhesive in number of cycles to failure.