结构用平压毛竹集成材单轴本构关系研究

Research on constitutive relationship of flat-pressure laminated moso bamboo lumber for structural application

为研究平压毛竹集成材单轴拉压状态下的应力-应变本构关系,以5年生毛竹的根部、中部和稍部为原料按照1∶1∶1的比例制备的毛竹集成材试件为研究对象。探讨了毛竹集成材受拉和受压状态下的破坏模式及应力-应变全过程曲线。研究结果表明:毛竹集成材的受拉破坏表现出典型的脆性拉断破坏;毛竹集成材的受压破坏属于延性破坏,具体表现3种典型破坏模式:纤维纵向撕裂、竹片层间开裂和褶皱破坏,经历了3个破坏阶段,即线弹性阶段、弹塑性阶段和加速破坏段。对于毛竹集成材单轴受拉应力-应变关系,提出了线弹性模型;对于毛竹集成材单轴受压应力-应变关系,提出了三折线模型和多项式模型,理论模型结果和试验结果吻合较好,为毛竹集成材结构有限元分析提供研究基础。

To study the stress-strain constitutive relationship of the flat-pressure laminated moso bamboo lumber(LBL) under the condition of uniaxial tension and compression, the bottom, middle and top of moso bamboo culms, aged 5 years old, was selected as raw material to fabricate LBL specimen according to the weight ratio of 1∶1∶1 as the research object. The failure mode, stress-strain curve of the whole process of LBL in tension and compression was discussed. The results show that the LBL in tension is featured by brittle failure, while ductile failure for compression. It is observed that there are three main failure modes: longitudinal fiber tearing failure, end cracks and central cracks between bamboo layers, and surface folding. The whole damage process can be divided into three stages, the linear elastic stage, the elastic-plastic stage and accelerated failure stage. For the uniaxial tensile stress-strain relationship of LBL, a linear elastic stress-strain model is suggested. For the uniaxial compressive stress-strain relationship of LBL, the trilinear and polynomial models are proposed, and the results obtained by the theoretic models are in good agreement with experiment results. The results provide a research foundation for the finite element analysis design of LBL structures.