竹材宏观微观力学性能试验与数值模拟

Experimental study and numerical simulation on the macro and micro mechanical properties of bamboo

竹材是一种力学性能优异、可再生和环保的结构性材料,具有广阔的工程应用前景。准确掌握竹材各组分的力学性能参数对于竹材的工程应用具有重要意义。结合细观力学和材料力学方法得到了一种确定竹材纤维和基体材料力学性能参数的计算方法:首先通过竹材试件的准静态压缩、拉伸和弯曲试验,获得了竹材在不同加载条件下的宏观力学性能;然后结合细观力学和材料力学分析方法,得到了竹材纤维和基体的力学性能参数;在此基础上,建立了竹材的有限元分析模型并进行数值模拟。结果表明,顺纹压缩时,竹材屈服后经历了一个强化段,然后由于纤维的屈曲失稳导致压缩应力发生下降,降至一个较低值后再次升高,并逐渐被压实;而横纹压缩表现出的力学性能与普通泡沫材料较为相似,在弹性段之后进入线性弱强化阶段,随后进入致密化阶段。竹材的顺纹拉伸过程为典型脆性材料断裂过程。受弯曲载荷作用时,在达到最大荷载前变形可近似视为线弹性过程,达到最大荷载之后随着位移的增加荷载逐渐下降。根据对试验结果分析所得到的竹材微观力学性能,仿真计算应力-应变曲线和试验结果误差在10%以内,验证了以上分析方法和模型的有效性。

With the increasing scarcity of natural resources and human beings’emphasis on the ecological environment,bamboo is a type of renewable and environmentally friendly structural material with excellent mechanical properties,which has the characteristics of fast growth,high yield,and excellent mechanical properties,so that it has wide engineering application potential.It is of great significance to accurately obtain the mechanical properties of each component of bamboo structure because its mechanical properties and failure rules depend on its mechanical properties.In this study,a calculation method for determining the mechanical properties of bamboo fiber and matrix material was presented by combining the methods of meso-mechanics and material mechanics,and the macroscopic mechanical properties of bamboo specimens under different loading conditions were obtained by quasi-static compression,tension and bending tests.Then,the mechanical properties of bamboo fiber and matrix were obtained by means of the meso-mechanical and material mechanical analysis.Based on the macroscopic tests and mechanical properties of the bamboo fiber and matrix,the finite element analysis model was established,and numerical simulations for the compression and tensile tests were carried out.The results showed that the bamboo underwent a strengthening period after yielding du-ring the longitudinal compression,and then the compressive stress decreased due to the buckling instability of the bamboo fibers,and then increased again after decreasing to a low value,and was gradually compacted.The mechanical properties of the transverse compression were similar to those of ordinary foam materials,which entered the linear weak strengthening stage after the elastic stage,and then into the densification stage.The tensile process of bamboo was a typical brittle material fracture.Under a bending load,the process could be approximated as the linear elastic process until the maximum load was reached,after the load decreased gradually with the increase of displacement.Based on the mechanical performance tests of the macroscopic compression,tension and bending,the mechanical performance parameters of each component of the bamboo specimens were obtained by combining the methods of micromechanics and mechanics of materials.According to the characteristics of bamboo,the finite element model of the bamboo compression and stretching was established,and the mechanical parameters of fibers and matrix materials were used for the simulation process.The simulation results were compared with the experiments,the errors of the stress-strain curve between simulation and test results were smaller than 10%,which verified the validity of the numerical simulation method and material parameters,and provided a reference for future research.