摘要
目的针对碳纤维增强树脂基复合材料(CFRP)在长期服役过程中的老化损伤导致的构件承载性能下降,严重威胁航空大型构件的服役可靠性,探索早期老化损伤的无损评价方法。方法以T300/AG-80热氧老化为对象,基于材料分析方法研究性能变化规律,结合超声脉冲回波方法研究了声学特性响应。结果150℃热氧老化后,样品质量损失率迅速上升,后缓慢增加,据此将整个老化过程分为老化初期、中期和后期3个阶段。提取不同老化阶段对应纵波声速、时域和频域声衰减系数发现,不同测试频率下,纵波声速均呈先下降、后升高、再下降的趋势,一次底波中心频率(约6 MHz)和二次底波中心频率(约4 MHz)对应频域声衰减系数与声速变化趋势呈负相关关系,时域和低频(约2MHz)声衰减系数变化不明显。结论结合微观组织和结构分析探讨了热氧老化及其声学响应机制,发现3个老化阶段分别对应水分子等低分子量物质挥发、树脂基体后固化、界面损伤和分子链断裂等物理化学演变,孔隙、界面裂纹等老化损伤及树脂的后固化作用综合影响超声波传播行为。研究结果为复合材料早期老化损伤的无损评价提供了参考。
The damage of carbon fiber reinforced plastic(CFRP)during long-term aging would lead to the deterioration of mechanical properties of large components,which seriously threatens the service reliability of large components.The thermo-oxidative aging of T300/AG-80 was studied based on material analysis and ultrasonic pulse-echo method and the evolution of acoustic properties was analyzed to explore the feasibility of nondestructive evaluation of early-stage damage.When the environmental temperature was 150℃,the weight loss ratio of the CFRP laminate increased rapidly first,and then increased slowly.Accordingly,the whole process was divided into three stages:initial,middle and later stages.The corresponding longitudinal wave velocity and attenuation coefficients in time and frequency domains were extracted.It was found that the velocity decreased first,then increased and finally decreased.The attenuation coefficients corresponding to the center frequencies of the first bottom echo(about 6 MHz)and the second bottom echo(about 4 MHz)were negatively correlated with the wave velocity,while the attenuation coefficients in time domain and low frequency(about 2 MHz)did not change significantly.The mechanism of thermo-oxidative aging and the corresponding acoustic response are discussed in combination with microstructure analysis.It is found that the three stages respectively correspond to volatilization of low molecular weight substances such as water molecules,post-cure effect of resin matrix,interfacial damage and fracture of molecular chain.As a consequence,damages such as pores,interfacial cracks and post-curing of resin result in comprehensive effects on ultrasonic propagation behaviors.The results would provide a reference for nondestructive evaluation of early-stage aging damage of composites.
作者
李云鹏
徐振业
邹野
金士杰
罗忠兵
LI Yunpeng;XU Zhenye;ZOU Ye;JIN Shijie;LUO Zhongbing(NDT&E Laboratory,Dalian University of Technology,Liaoning Dalian 116024,China;The Aeronautical Science Key Lab for High Performance Electromagnetic Windows,The Research Institute for Special Structures of Aeronautical Composite AVIC,Jinan 250023,China)
出处
《装备环境工程》
2025年第3期18-25,共8页
Equipment Environmental Engineering
基金
国家自然科学基金(52375527,52275520)。
关键词
CFRP
复合材料
热氧老化
微损伤
超声
无损评价
CFRP
composite
thermo-oxidative aging
microdamage
ultrasonic
nondestructive evaluation
