竹单层顺纹拉伸性能测试与分析

Examination of bamboo single layer linear tensile property

竹材中纤维束密度从竹黄到竹青沿径向逐层增加,为了获得竹材任意单层的顺纹拉伸性能,基于竹材的层合特性,提出从竹青、竹黄两面逼近的削减法。从竹青、竹黄两侧按一定厚度依次削减至竹片中心层以获得不同厚度的测试试件,并测得其顺纹拉伸性能。研究建立竹单层与削减后试件的拉伸力学关系模型,获得相应竹单层的顺纹弹性模量及拉伸强度。通过对毛竹顺纹拉伸试验及计算分析,获得了沿径向弹性模量、拉伸强度的数学表达式;各单层的弹性模量与拉伸强度的计算式分别为E=5.86+34.02/[1+(x/1.34)^(2.21)]和σ=86.21+505.2/[1+(x/1.34)^(2.19)]。结果表明:毛竹的各层力学性能从竹青层至竹黄层逐渐递减;单层计算式误差随分层数增加而减小,当取单层厚度为0.5 mm(16等分)时,其竹材弹性模量与拉伸强度计算值与试验值的误差分别为2.41%,4.26%。本研究获得了毛竹顺纹弹性模量及拉伸强度沿径向的变化规律,对竹单层计算精度高,为竹材力学性能分析及利用提供了一种有效的方法。

As one of the important forest resources,bamboo has advantages of excellent mechanical properties,environmental-friendly,short growth cycle,widespread distribution,and long service life,having a wide range of application value and sustainable development.It has been widely used in construction,furniture,textiles,and other fields.However,in the process of bamboo and the preparation of bamboo fiber,it is necessary to understand the linear tensile properties of materials at different thickness positions to improve the utilization rate and product quality of bamboo.In order to obtain the tensile properties of any single layer of bamboo along its grain direction,a cutting method that approaches from both the green and yellow sides of bamboo based on its laminated characteristics was proposed.From both sides of bamboo green and bamboo yellow,a certain thickness was cut to the center layer of bamboo sheet to obtain test specimens of different thicknesses,and their smooth tensile properties were measured.The tensile mechanical relationship model between the bamboo monolayer and the reduced specimen was studied,and the elastic modulus and tensile strength of the corresponding bamboo monolayer were obtained.By conducting tensile tests on bamboo along its grain direction and analyzing the results,mathematical equations for estimating the elastic modulus(E)and tensile strength(σ)of each single layer of bamboo were obtained.The calculation formulas for the elastic modulus and tensile strength of each single layer were E=5.86+34.02/[1+(x/1.34)^(2.21)]andσ=86.21+505.2/[1+(x/1.34)^(2.19)],respectively.The results showed that the mechanical properties of each layer of moso bamboo gradually decreased from the green layer to the yellow layer.The error of the calculation formula for each single layer decreased as the number of layers increased,when the thickness of each single layer was 0.8 mm(10 equal parts),the error between the calculated values of elastic modulus and tensile strength of bamboo and their experimental values were 10.97%and 10.68%,respectively.When the thickness of each single layer was 0.5 mm(16 equal parts),the error between the calculated values of elastic modulus and tensile strength of bamboo and their experimental values were 2.41%and 4.26%,respectively.This study obtained the variation law of the elastic modulus and tensile strength along the radial direction of moso bamboo,which has high accuracy in calculating single-layer bamboo,providing an effective method for mechanical property analysis and utilization of bamboo.