ABSTRACT

The increasing use of honeycomb structures in the aircraft industry has demonstrated the need for the development of more effective evaluation methodologies. In recent years, thermography has received vast and growing attention as a reliable technique for non-destructive testing and evaluation of composite materials due to its remarkable advantages of non-contact, full area coverage, high speed, safe and convenient operation, qualitative and quantitative inspection capabilities. In this paper, Lock-in thermography is employed to inspect water ingress in aircraft honeycomb structures, and an investigation into the effect of water content on the quantitative estimation has been carried out. A square-shaped composite honeycomb panel of dimension 300 × 300 mm with four equal size defective areas of 50 × 50 mm as the groups of cells filled with water by 25%, 50%, 75% and 100% of the cell volume was considered as a test sample. The sample was excited at multiple modulation frequencies, viz., 0.5 Hz, 0.2 Hz, 0.1 Hz, 0.05 Hz, 0.02 Hz, and 0.01 Hz. Three Lock-in thermography algorithms, namely, Fast Fourier transform, Harmonic approximation, and Principle component analysis, are discussed for quantitative assessment; and their performance is compared in terms of Signal to noise ratio.

摘要

飞机工业中蜂窝结构的使用越来越多，这表明需要开发更有效的评估方法。近年来，热成像技术以其非接触，全覆盖，高速，安全，方便，定性和定量的显着优势，作为一种可靠的复合材料无损检测和评估技术，受到了越来越多的关注。检查功能。本文采用锁定热成像技术对飞机蜂窝结构中的水分进入进行了检查，并研究了水分含量对定量估计的影响。考虑了尺寸为300×300 mm的方形复合蜂窝板，其中四个相等尺寸的缺陷区域为50×50 mm，这是单元格中充满水的单元格，分别填充了单元格体积的25％，50％，75％和100％作为测试样本。以多个调制频率，即0.5 Hz，0.2 Hz，0.1 Hz，0.05 Hz，0.02 Hz和0.01 Hz激发样品。讨论了三种锁定热成像算法，即快速傅里叶变换，谐波近似和主成分分析，以进行定量评估；并根据信噪比比较它们的性能。讨论了快速傅里叶变换，谐波近似和主成分分析以进行定量评估；并根据信噪比比较它们的性能。讨论了快速傅里叶变换，谐波近似和主成分分析以进行定量评估；并根据信噪比比较它们的性能。