碳纤维/双马来酰亚胺复合材料的拉-拉疲劳性能

 <正> 复合材料的疲劳性能数据比一般金属材料都要更加分散,通常采用威布尔分布进行统计处理。金属材料的疲劳研究也已提出了许多有用的研究方法,得到许多广为采用的疲劳性能表达式。但这些方法和公式是否能用于任何复合材料的研究是引人注意的问题。

FATIGUE BEHAVIOUR OF CARBON/BISMILIMIDE COMPOSITE UNDER TENSION-TENSION LOADING

In the present study a formula is proposed to predict the fatigue life of the composite which is made of the matrix of bismi-limide and unidirectionally reinforced by 66% T-300 carbon fibre by volume. All fatigue tests were carried out at stress ratio R=0.1 and f=5 Hz and the endurance limit was determined by up-down method. Test results show that the fatigue life of this composite approximately follows log-normal distribution and that the endurance limit is about 70% of the ultimate stress. The fatigue life test results can be well expressed by the follwing expression: Nt = A' (σmax -σc)-2, where A' may be referred as the fatigue resistance coefficient approximately equal to the square of ultimate stress of this composite? A' = 1.78×106 MPa, and σc may be defined as the theoretical endurance limit, σc=922MPa. Besides, the mechanism of fatigue damage of this composite was also observed and analysed.