Effect of pre-fatigue on bending behavior of 2.5D C/C composites

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• 作者：Xiao Li^a ; Shu Yu^a ; ^{yushu@csu.edu.cn} ; Yunping Li^b ; Qiang Wu^a ; Zhuan Li^a ; Tao Xiao^c ; Lihong Liu^c ; Xiaoning Guo^c
• 关键词：Bending strength ; Pre-fatigue ; Stress level ; Interface
• 刊名：Materials Science and Engineering: A
• 出版年：2017
• 出版时间：13 January 2017
• 年：2017
• 卷：682
• 期：Complete
• 页码：290-295
• 全文大小：1524 K
• 卷排序：682

文摘

This study investigates the influence of pre-fatigue on the bending behavior of needle-punctured 2.5D C/C composites with density between 1.75 and 1.80 g/cm3 prepared by chemical vapor deposition (CVD). Three-point bending pre-fatigue tests are carried out under applied stress/static flexural strength ratio of 60%, 70%, 80% and 90% up to one million cycles. The results show that except for the 60% sample, flexural bending strength of most samples subjected to pre-fatigue is improved significantly compared with that without pre-fatigue. Detailed investigation indicates that the subsequent bending behavior of sample is closely related to both stress level in pre-fatigue and the resultant microstructure. Under low stress level (60–70%) during pre-fatigue, the composite is characterized by a plastic deformation and a slight enhancement of bending strength ascribed to the weakened fiber/matrix interface after fatigue. After pre-fatigue with high stress level (80–90%), the composite demonstrates brittle failure mode but much higher residual strengths during subsequent bending test. The reason for this is ascribed to the variation of the microstructure in fiber/matrix interface during the pre-fatigue, which strongly affects the subsequent mechanical responses.