竹材Ⅲ型层间的断裂韧性

摘要

采用改进设计的端部切口悬臂梁(SCB)装置,试验测试毛竹(Phyllostachs pubescens)Ⅲ型层间断裂性质,并分别用柔度法和面积法计算其Ⅲ型层间断裂韧性值.结果表明:(1)采用柔度法和面积法得到的Ⅲ型层间断裂韧性,分别为2.38 N·m-1(标准差0.74 N·m-1)、2.20 N·m-1(标准差0.36 N·m-1),前者略高于后者,但方差分析差异不显著;(2)二种方法测得的Ⅲ型层间断裂韧性,基本上与裂纹尺寸无关,说明层间断裂韧性是竹材的一种基本性质;(3)对竹材断面的观察发现,Ⅲ型层间裂纹在未木质化的短型基本组织细胞中的扩展是伴随着胞壁的撕裂,但在已木质化的长型基本组织细胞之间和纤维束之间,裂纹是沿胞间层扩展的.%A modified split cantilever beam (SCB) equipment was employed to test fracture toughness of the moso bamboo (Phyllostachs pubescens) Ⅲ mode interlaminar.The moso bamboo Ⅲ mode interlaminar fracture toughness was calculated and analyzed by compliance and area method.The fracture toughness tested by compliance and area method was 2.38 N ·m-1 with standard deviation of 0.74 N · m-1 and 2.20 N · m-1 with standard deviation of 0.36 N · m-1,the former was 8.18％ higher than the later,and the variance analysis results were not significant.The interlaminar fracture toughness tested by the two methods was basically unrelated with the crack size,which indicated that the interlaminar fracture toughness of bamboo was the basic property of material.By analyzing the interlaminar fracture characteristics and fracture surface,Ⅲ mode crack propagation accompanied with the tearing of long cell and the cracking of short cell in basic tissues,and the cracking of fiber bundles was wrapped by basic tissues and the interlaminar of fiber bundle and vascular bundle with the interfaces of basic tissue.