超低温处理对T700碳纤维/环氧复合材料拉—压疲劳性能的影响

Effect of Cryogenic Treatment on Tension-Compression Fatigue Properties of T700 /Epoxy Composite

对T700碳纤维/环氧复合材料在超低温处理前后的拉—压疲劳性能进行了的研究。采用真空袋—热压罐成型工艺,制备了T700碳纤维/环氧复合材料单向板,在液氮中对试样进行超低温浸泡和超低温/室温循环处理,利用光学显微镜观测了试样在超低温处理过程中产生的微裂纹情况,并测试了超低温处理后试样的静强度和拉—压疲劳1000次、10000次及130000次后的剩余强度。对T700碳纤维/环氧复合材料超低温损伤机理进行了分析,并讨论了超低温处理和拉—压疲劳对复合材料剩余强度的影响。结果表明,超低温处理和拉—压疲劳处理都会使试样产生微裂纹,并引起试样内的残余应力释放和试样的剩余强度降低;经历不同的超低温处理之后,试样的剩余强度达到最高值时所对应的拉—压疲劳次数不同;随着超低温处理和拉—压疲劳的作用,试样的剩余强度会经历先升高—再降低的过程。

Tensile-compression fatigue properties of T700 carbon fibers/epoxy composite materials after cryogenic treatment are studied in this paper. The unidirectional T700 carbon fibers/epoxy composite materials are manufactured by using a vacuum bag-autoclave moulding-process. In liquid nitrogen, the samples are treated through cryogenic immersing and cryogenic/room temperature cycling respectively. Microcracks of samples after cryogenic treatment are investigated by using a optics microscope. Both static strength and residual strength after tensile-compression fatigue 1000 times, 10000 times and 130000 times of samples are investigated after the cryogenic treatment. Cryogenic damage mechanism of T700 carbon fibers/epoxy composite material is analyzed. The influence of cryogenic treatment and tensile-compression fatigue on residual strength of the composite material is discussed. As the results shown, microcracks will be presented after the cryogenic treatment or tensile-compression fatigue. And the microcraeks will cause releasing residual stress and reducing residual strength. The times of tensile-compression fatigue is different when the residual strengths come to the maximum for the samples after different cryogenic treatment. The residual strengths of samples will first raise and then lower with different cryogenic treatments and tensile-compression fatigues.