碳纤维复合材料自行车前叉冲击-疲劳测试的声发射研究

Acoustic emission study on impact-fatigue test of carbon fiber composite bicycle front fork

为建立碳纤维复合材料自行车前叉的可靠性检测评价方法,采用声发射(Acoustic Emission,简称AE)方法研究了前叉在冲击-疲劳过程中损伤的萌生和扩展。采用落锤冲击模拟前叉在役过程产生的缺陷,采集循环加载疲劳实验过程中的AE撞击数、峰值振幅、持续时间等AE信号;通过AE线性定位图判断前叉内部损伤产生的位置,并利用AE频域波形快速傅里叶变换(Fast Fourier Transform,简称FFT)分析损伤特征。结果显示:落锤冲击载荷下,前叉会产生基体开裂、分层等微观损伤,且发生在前叉叉骨部位;疲劳实验中,前叉的损伤破坏经历了初始阶段、平稳扩展期和最终阶段,各阶段分别出现基体破坏、界面分层、纤维破坏等损伤模式,损伤演化呈渐进式增长;当AE峰值振幅和能量同时达到100dB和7.73×10^(10)eu时,复合材料中的碳纤维有32.36%发生断裂而导致前叉彻底失效。研究结果表明,在CFRP复合材料的冲击-疲劳过程中,AE参数的响应和损伤的形成与发展有密切关系,AE信号特征规律能够被用来指导碳纤维自行车前叉的结构设计,也能对在役前叉部件的健康状态进行监测以便及时修复受损伤部位。

In order to establish a reliable evaluation method for bicycle front fork made of carbon fiber composite,the Acoustic Emission(AE)method was used to investigate the damage initiation and propagation in front fork during impact-fatigue test.The front fork was subjected to drop hammer impact and cyclic loading fatigue tests,and the corresponding AE hit number,peak amplitude,duration and other parameters were detected in real time.The AE linear location maps were used to locate the position of internal damage,and the Fast Fourier Transform(FFT)diagrams of AE frequency domain waveform were used to analyze the damage characteristics.The results show that the matrix cracking and delamination will generate in the wishbone part of front fork during the hammer impact test.During the fatigue test,the damage will experience three stages(initial stage,smooth extension stage and final stages),which correspond to the matrix failure,interfacial stratification and fiber failure,respectively.The damage development of front fork is a gradual growth process.When the peak amplitude and energy of AE reach to 100dB and 7.73×10^(10) eu,32.36%of the carbon fibers in the composite were broken,resulting in the complete failure of the front fork.The response of AE parameters is closely related to the formation and development of damage in the impact fatigue process of CFRP composites.This AE method could not only provide basic data for structural design of bicycle front fork but also monitor the health status of in-service front fork components,which is convenient to take timely repair work.