不同端压下杨木指接质量的分析

Effects of end pressures on the finger-joint quality of poplar wood

以力学性能测试和指榫显微分析相结合的方法,评价不同端压下杨木的指接质量,并分析最佳端压;利用端压-位移曲线,得到了杨木指接的理论端压范围。在此基础上,从3.0～16.5 MPa范围内选取5个端压水平进行指接实验及质量分析。结果发现,端压对指接材的抗弯弹性模量无显著影响,但对抗弯强度和抗拉强度影响显著。显微分析显示,当端压小于最小临界压力Pmin时,指榫不能完全嵌合,胶层含有气泡;当压力超过7.6MPa时,指榫纤维严重扭曲,压溃和劈裂现象明显,两种情况都无法获得最佳的力学性能。综合分析可得,在实验齿榫参数条件下,杨木指接的理想端压为7.0 MPa,约为材料抗压强度的20%。

Finger-joint quality is one of the key factors to the performance of wood products.The aim of this research was to evaluate the effect of end pressure on the quality of finger-joint of poplar and find the best end pressure by mechanical property test and microscopic analysis.The theoretical range of end pressure was firstly determined by examining load-displacement curves,and then five end pressure levels ranging from 3.0 MPa to 16.5 MPa were investigated based on the the theoretical range of end pressure.Test results showed that the end pressure did not affect on the modulus of elasticity.However,the effects on the modulus of rupture and tensile strength were significant.When the pressure was lower than critical pressure Pmin,finger tip could not contact with finger root completely.Meanwhile,the crush and crack of joints increased markedly as the pressure exceeded 7.6 MPa.Both of the two situations were unable to obtain the best finger joint strength.It can be observed that the best end pressure for finger jointed poplar is about 7.0 MPa in this experiment,which is about 20% of the compressive strength of the material.