摘要
纤维增强树脂基复合材料(Fiber reinforced plastic,FRP)具有强度高、密度低、抗疲劳、可设计性强等优点,自被开发以后便迅速在航空航天等现代工程领域得到广泛应用。随着对FRP失效机理研究的深入及工程设计水平的提高,工程中FRP材料的设计许用值逐渐提高,FRP材料的疲劳问题变得不容忽视。尤其是高铁、飞机结构中的FRP材料,常常由于气动原因承受着高频振动载荷,从而引发FRP材料的超高周疲劳(Very high cycle fatigue,VHCF)失效问题。对FRP材料的超高周疲劳问题的研究主要分为四个方面:(1)FRP超高周疲劳试验方法;(2)FRP超高周疲劳损伤机理;(3)FRP超高周疲劳性能曲线特征;(4)FRP超高周疲劳寿命预测方法。其中疲劳试验方法为研究提供基本试验数据,是所有研究中最基础的部分。FRP超高周疲劳试验技术主要沿用金属材料的超高周疲劳试验方法,但由于FRP材料阻尼大、导热性差且对温度敏感,难以直接提高试验的加载频率。目前,主要采用减小试验件厚度、间歇加载以及强制冷却等手段来控制试验件温度,从而提高加载频率,缩短FRP超高周疲劳试验时间。超高周疲劳与常规疲劳的本质差别在于疲劳损伤机理的差异。超高周疲劳载荷下,FRP材料的基体裂纹损伤可能转变为局部点蚀,并且分层损伤可能先于基体裂纹萌生,这与典型的“三阶段”损伤演化过程有所不同。超高周疲劳载荷下,FRP材料的S-N曲线也表现出三种不同形式,分别对应存在疲劳极限、疲劳强度持续下降以及疲劳强度阶梯式下降三种情况。FRP超高周疲劳寿命预测方法主要沿用FRP常规疲劳寿命预测方法,其中基体裂纹密度方法可以降低对超高周试验数据的依赖程度。目前对FRP超高周疲劳损伤演化及性能曲线等问题的研究停留在对试验结果的观察阶段,缺乏系统的总结与研究。本文回顾了FRP材料超高周疲劳问题的研究进展,对FRP超高周疲劳研究的四个方面的内容进行了详细介绍。通过对现有研究成果进行对比分析,提出了FRP超高周疲劳需要深入研究的问题。
Since the early development,fiber reinforced plastic(FRP)materials have been widely used in aerospace and other modern engineeringfields due to their advantages of high strength,low density,anti-fatigue property and excellent designability.With the in-depth study of FRPf ailure mechanism and the improvement of design level,the design admissibility of FRP materials in engineering has been gradually enhanced,and the fatigue problem of FRP materials can not be ignored anymore.In particular,the FRP materials in high-speed railway and aircraft structures often bear high-frequency vibration load due to aerodynamic force,which leads to very high cycle fatigue(VHCF)failure of FRP materials.The research on very high cycle fatigue of FRP mainly focuses on the four aspects,VHCF test methods,VHCF damage mechanism,the characteristics of VHCF performance curve and VHCF life prediction methods.Among them,the fatigue test methods provide basic test data,which is the most fundamental part of the research work.The VHCF tests of FRP mainly adopt the VHCF test methods of metallic materials.However,due to the large damping,poor thermal conductivity and high temperature sensitivity of FRP materials,it is difficult to directly increase the load frequency in FRP VHCF tests.At present,it is mainly by reducing the thickness of the specimen,applying intermittent load and cooling that the control of specimen temperature is carried out,with the load frequency increased and the test time of VHCF shortened.The essential difference between VHCF and conventional fatigue lies in the difference of fatigue damage mechanism.Under very high cycle fatigue load,the matrix crack damage of FRP materials may be transformed into local pitting corrosion,and the delamination damage may initiate before the matrix crack,which is different from the typical three-stage damage evolution process.Under the very high cycle fatigue load,the S-N curve of FRP materials also shows three different forms,respectively corresponding to the existence of fatigue limit,continuous decrease of fatigue strength and step-like decrease of fatigue strength.The VHCF life prediction methods of FRP mainly follow the conventional non-VHCF fatigue life prediction methods,in which the matrix crack density methods have a reduced dependence on the very high cycle fatigue experiment data.At present,the research on damage evolution and performance curve of FRP materials under VHCF is limited to the observation-dominant methods,which lacks systematic research and summary.In this paper,the recent research of very high cycle fatigue of FRP is reviewed,and the above-mentioned four aspects have been introduced in detail.Based on the comparative analysis of existing research results,the problems of very high cycle fatigue of FRP that need to be further studied have been put forward.
作者
吴涛
姚卫星
黄杰
WU Tao;YAO Weixing;HUANG Jie(Key Laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle,Nanjing University of Aeronautics and Astronau-tics,Nanjing 210016,China;State Key Laboratory of Mechanics and Control of Mechanical Structures,Nanjing University of Aeronautics and Astronautics,Nanjing 210016,China)
出处
《材料导报》
EI
CAS
CSCD
北大核心
2022年第6期210-218,共9页
Materials Reports
基金
国家自然科学基金(52002181)。
作者简介
吴涛,2015年9月毕业于南京航空航天大学,获得工学学士学位。2021年6月毕业于南京航空航天大学,获得工学博士学位。目前于南京航空航天大学能源与动力学院从事博士后研究工作,主要研究领域为飞行器结构设计及先进复合材料结构设计;姚卫星,1982年5月毕业于西北工业大学,获得工学学士学位。1984年5月毕业于西北工业大学,获得工学硕士学位。1988年5月毕业于西北工业大学,获得工学博士学位。目前任南京航空航天大学教授、博士研究生导师。主要从事复合材料结构制造⁃工艺一体化设计、飞行器的总体⁃气动⁃结构的综合设计技术、结构抗疲劳设计等领域研究。共发表学术论文150多篇,出版专著、教材3部。wxyao@nuaa.edu.cn。
