摘要
为了研究木基缠绕管用复合板带的偏轴力学性能,按照与复合板带较厚层的顺纹方向成0°,15°,30°,45°,60°,75°和90°制备试样进行拉伸试验,根据是否添加纤维布得到了2种复合板带各7种破坏形式、应力-应变曲线、泊松比、弹性模量和拉伸强度。通过数值拟合、Transformation law公式、Hankinsion公式、最大应力强度准则以及蔡-希尔强度准则对板带力学性能进行分析预测。结果表明:复合板带的破坏形式主要为单板顺纹方向的纤维拉断和横纹方向的剪切破坏,纤维布的加入加剧了剪切破坏;在偏轴应力下,0°到90°复合板带试样的承载力、弹性模量和拉伸强度随偏轴角的增大呈先降低再增大的变化规律,且在47°下取得最低值;泊松比随偏轴角的增大呈先增大后降低的变化规律。未加纤维布复合板带的弹性模量可以通过Transformation law公式准确预测;泊松比可以通过数值拟合的二次函数准确预测;拉伸强度可以通过蔡-希尔强度准则预测。而纤维布加入到复合板带中,会使其受偏轴拉伸载荷时的应力-应变更加复杂,力学性能的试验值与预测结果误差较大。
Usually,water pipes are made from concrete,PVC,ductile iron,polypropylene,which cause the emission of greenhouse gas(GHG)and affect the environments.In order to reduce the GHG emission in China,the fast-growing wood was used to develop green and environmental-friendly wood-based winding pipes.The structural layer of the pipe was formed by the multi-layer winding of poplar veneer strips at a certain winding angle,where the veneer strip was made of two poplar veneer layers of different thicknesses with sound flexibility.The off-axis direction was the main direction for the veneer strips to bear internal pressures.Therefore,it is necessary to study the mechanical properties of the structural layer to reveal the off-axis mechanical properties of veneers.According to whether the fiber cloth reinforcement layer was added,tensile tests were carried out on specimens prepared in the direction of 0°,15°,30°,45°,60°,75°or 90°along the grain direction of the thicker layer of the composite strips.The failure modes,stress-strain curves,Poisson s ratio,Young s modulus and tensile strength of the seven groups of samples were obtained.Through numerical fitting,Transformation law formula,Hankinsion formula,maximum stress intensity criterion and Tsai-Hill strength criterion,the relevant mechanical properties of the veneer strips were analyzed and predicted.The results showed that the failure modes of the veneer strips were mainly the fiber pull-off from the veneer and the shear failure along the grain direction,moreover,the addition of fiber cloth made the shear failure of the veneer strip more serious.Under the off-axis stress,the bearing capacity,the Young s modulus and tensile strength of the veneer strips was reduced firstly and then increased,and reached their minimum value at 47°.The Poisson s ratio of the two veneer strips increased firstly and then decreased with the increase of the off-axis angle.The Young s modulus of the un-fibered veneer strip could be accurately predicted by the Transformation law formula;the Poisson s ratio could be accurately predicted by the quadratic function of the numerical fitting,and the tensile strength of the veneer strip could be predicted by the Tsai-Hill strength criterion,while the maximum stress intensity criterion was accurate only between 0°and 70°.As the fiber cloth was added to the veneer strip,the stress-strain was more complicated when subjected to the off-axis tensile load,and the experimental values of the mechanical properties deviated greatly from the predicted results.
作者
候兴爱
孙丰文
钱曹厉
HOU Xing ai;SUN Fengwen;QIAN Caoli(College of Materials Science and Engineering,Nanjing Forestry University,Nanjing 210037,China)
出处
《林业工程学报》
CSCD
北大核心
2019年第4期22-28,共7页
Journal of Forestry Engineering
基金
“十三五”国家重点研发计划(2018YFD0600305)
关键词
木基缠绕管
偏轴拉伸
弹性模量
拉伸强度
泊松比
wood-based winding pipe
off-axis tensile
Young s modulus
tensile strength
Poisson s ratio
