竹材层合板弯曲破坏机理的实验研究

Experimental Studies on Bending Failure Mechanics of Bamboo Laminate

竹材层合板是为了满足一定的使用要求,由多层单向板按同一方向整齐排列、胶合、加热固化处理而成的复合结构体。由于竹材层合板的各向异性和非均匀性,它的力学行为十分复杂,特别是弯曲时不仅各个单层产生损伤破坏,而且伴随着层间胶接层的开裂。本文对竹材层合板的弯曲破坏特征进行实验研究;一系列包含变形信息的数字散斑图像被记录;采用数字散斑相关技术(DSCM)提取了三点弯曲变形过程中的面内位移场信息,分析了不同变形阶段的位移场;给出了不同弯曲变形阶段试件的应变场分布和应变集中现象;分析了中性轴在胶层开裂、层内纤维撕裂等复杂应力情况下的演化过程及规律。最终一些宏微观破坏机制被分析,例如基体开裂,界面损伤与撕裂,界面与裂纹作用等。这些研究结果将为竹材层合板的破坏机理等力学行为的研究和工程应用开发提供实验依据。

Bamboo laminate is a kind of composite structures, which is usually made from multi-layer plates by trim arrangement along the fiber direction, gluing, heating and solidifying in order to reach the requirements for use. Due to the anisotropy and non-homogeneity of bamboo laminate, its mechanical behaviors are very complicate. Especially, there is not only the failure of bamboo single layer but also the delaminating between the layers when a bamboo laminate is under bending loading. In this paper, the bending failure characteristics of bamboo laminate were analyzed. A series of speckle images with deformation information were recorded. In-plane displacement field information of bamboo laminate were extracted and analyzed by digital speckle correlation method (DSCM) during the process of three-point-bending test. Both the distribution of strain fields and the strain concentration was determined at every stage of bending deformation. The evolution of neutral axis was analyzed with delaminating of adhesive layers and tearing of bamboo layers. Finally, some macro/microscopic mechanisms are analyzed like matrix cracking, interface damage and delaminating interaction between the interface and crack. All these results will provide a reliable experiment basis for studying mechanical behaviors like failure mechanism and developing engineering application of bamboo laminate.