落叶松结构用胶合木层板指接工艺参数对力学性能的影响

Effects of Finger-jointing Parameters on Mechanical Properties of Dahurian Larch Laminate for Structural Glulam

以兴安落叶松刨光锯材制作胶合木指接层板,探讨指榫参数、指接压力和不同规格尺寸对锯材指接层板抗弯性能的影响。结果表明：指榫工艺参数对指接层板抗弯弹性模量影响较小,而对抗弯强度影响较大。当选用12.7、19mm和25mm指榫长度及其相应的指接工艺参数时,层板抗弯强度平均值和5%分位值均能达到国家标准GB/T 26899-2011《结构用集成材》目测分等Ⅰ_d等级和机械分等M_E14等级规定值,对于中小截面胶合木层板,尽可能考虑选用12.7~19mm范围内较小的指榫长度进行指接加工以利节材。在指接过程中应选用合适的指接压力,指接压力过大或过小都会对指接层板抗弯性能尤其强度造成不利影响,指接层板抗弯强度的尺寸效应与非指接锯材相似。

Samples of Dahunan Larch（Larix gmelini） saw timber were selected in this study to examine the influences of finger-jointing parameters,finger-jointing pressure and size of laminates on the bending properties of finger-jointed laminate.The results show finger-jointing parameters have much more effect on bending strength（MOR）but less effect on bending modulus（MOE）.When 12.7,19mm and25mm of finger joint length are used,and other parameters are reasonable,the average test value and5-percentile characteristic test value of MOR can reach the requirements on visual grade Id and MSR grade M_E14 specified in GB/T 26899-2011《Structural Glued Laminated Timber》.For glulam with medium and small cross section,12.7~19mm of finger joint length should be used.Also,finger joint pressure should be reasonable because either too large or too small pressure can cause adverse impact on bending properties.For the finger jointed laminates of Dahurian Larch with cross section of 40mm×90mm and 40mm×65mm,their size effect on bending properties is similar to that of non-finger jointed lumber.