三种典型竹质工程材料纵向弹性模量评价

Evaluation of Longitudinal Modulus of Elasticity of Three Typical Bamboo-based Engineering Materials

以重组竹、竹束单板层积材(BLVL)、竹集成材为代表的竹质工程材料受到越来越多的关注和应用。文中采用超声波法、自由横向振动法和力学法分别对上述3种典型竹质工程材料的纵向动态弹性模量(MOE)进行评价比较,结果表明,横向自由振动法能较为快速、准确和无损地评价出竹质工程材料的MOE,MOE的变异系数与其自身铺装结构有关;重组竹、BLVL和竹集成材的一阶共振频率分别为455.73、380.41和487.62 Hz;超声波在竹集成材的纵向上传播速度最快,重组竹其次,BLVL最慢;三点弯曲力学测试发现3种竹质工程材料的断裂模式不同,全顺向的重组竹为竹纤维拉断和界面剪切破坏,纵横组坯的BLVL为横向竹束拉断以及竹/木复合界面分层,而更多体现实竹性能的竹集成材为底层竹材维管束拉断和拔出破坏,其断裂载荷为重组竹>BLVL>竹集成材,而断裂位移为竹集成材>BLVL>重组竹。

Bamboo-based engineering materials such as bamboo scrimber,bamboo bundle laminated veneer lumber(BLVL)and glued laminated bamboo have attracted more and more attention and have been increasingly applied.The paper evaluates and compares the longitudinal dynamic modulus of elasticity(MOE)of the above three typical bamboo-based composites using ultrasonic method,free transverse vibration method and mechanical method,respectively.The results showed that,compared with other methods,the transverse free vibration method can evaluate the longitudinal dynamic elastic modulus of bamboo engineering materials more quickly,accurately and nondestructively.The coefficient of variation of MOE is related to its own pavement structure of the bamboo-based composites.The first-order resonance frequencies of bamboo scrimber,BLVL,and glued laminated bamboo are 455.73 hz,380.41 hz and 487.62 hz,respectively.Ultrasonic wave travels the fastest in the longitudinal direction of glued laminated bamboo,followed in bamboo scrimber and BLVL.3-point bending tests show that the fracture modes of the three types of bamboo engineering materials are different.Bamboo scrimber assembled all in longitudinal direction is fibers tensile and interfacial shear failure.Transverse bamboo bundle pulling and the delamination between bamboo/wood composite interface are the main fracture model for BLVL made of vertical and horizontal bamboo bundle layers,while the glued laminated bamboo,whose performance is similar to bamboo timber,presents the bamboo bundle pulling and fracture on the underlying layer.The fracture load is ordered as bamboo scrimber>BLVL>glued laminated bamboo,and the fracture displacement as Glued Laminated Bamboo>BLVL>Bamboo scrimber,respectively.