航空复合材料孔隙率的超声波衰减法检测

Estimation of Aeronautical Composite Porosity by Using Ultrasonic Wave Attenuation

以国内自主研制的首款全机身复合材料某型号飞机使用的复合材料板试件为试验样品,采用超声脉冲回波法对其进行孔隙率无损检测。对采集的超声回波射频信号进行希尔伯特变换(Hilbert Transform),并进一步滤波后得到一次底波和二次底波的包络信号,进而计算相应的声衰减系数;结合金相法抽检获得实际的孔隙率含量,标定得到超声波衰减系数与孔隙率含量之间的经验公式;利用该经验公式对余下的同一批复合材料进行孔隙率检测,并将预测结果与随后进行的金相法检测结果进行对比。试验表明,这些结果具有很好的一致性,说明该方法具有一定的实用性。

Ultrasonic techniques for measuring void content were discussed and the composites used for the whole fuselage composite aircraft developed independently in China were chosen as experimental specimens, including 10 unidirectional carbon fiber laminates and 10 textile glass fiber sheets. The ultrasonic RF signals were processed using Hilbert transform and spectral-filter and then used to calculate the acoustic attenuation. The relationship between attenuation coefficient and porosity was calibrated by sampling experiment based on metalloscopy. The calibrated relational expression was then used to estimate the porosity of the rest specimens. The experimental data showed that the ultrasound testing results were in agreement with the metallographic detection.