Bamboo is a kind of biologic composite material strengthened by fibers that distribute asymmetrically, and the property of toughness depends on the property of component material as well as the characteristic of meso-structure. The study showed that the whole process of bamboo transverse bending fracture includes the cracking of parenchyma tissue, the layering of interface, the fracture of bamboo fiber bundle and the pull-out of bamboo fiber bundle and other various damage patterns. Different organization structures contribute different toughness to the evolution of damage for different energy wastage. In order to find out the main structure factors that lead to the excellent toughness property, the meso-mechanics method was applied to study the energy absorbing mechanism of parenchyma tissue crack pattern and interface layering pattern during process of bamboo transverse bending fracture. Then the strain energy release rate analysis equation of the two patterns above was obtained and the critical strain energy release rate analysis equation of the bamboo specimens with crack perpendicular to grain loaded with bending load and the transverse crack transforming to initial crack along grain.%采用细观力学方法,研究竹材在横弯断裂过程中基本组织开裂与界面脱粘这2种损伤模式的能量吸收机制,并推导得到这2种损伤模式的应变能释放率解析式,以及含垂直纹理裂纹的竹试件在承受弯曲载荷时、横向裂纹转向顺纹启裂时的临界应变能释放率解析式.
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