Acoustic emission characterization of failure modes of single-lap joints in glass/epoxy specimens

Abstract

The main objective of this study is to predict the joint strength and frequency ranges for failure modes on single-lap joints of glass fiber/epoxy specimens under tensile loading, without causing much damage to the lap joint specimen. To design structural components using composite materials, a deep understanding about the material behavior and its failure modes are necessary. To create a better understanding of the adhesive failure, unstable growth and failure process monitoring during mechanical loading is important. Parametric analysis and multistage approach appears to be an efficient tool to correlate the mechanical behavior of composite single-lap joints namely bonded joint, riveted joint, and hybrid joint with acoustic response. The dominant failure modes and their characteristic frequency ranges are assigned to the different acoustic emission (AE) signal levels on the basis of AE waveform in the time domain using fast Fourier transform (FFT) analysis. FFT analysis is performed for the peak frequency ranges and the results are interpreted with respect to the amplitude and duration hit activity for each failure mode. The results obtained from AE parametric analysis are compared with FFT analysis results to find the peak frequency ranges for each failure mode. Scanning electron microscopy was used to categorize the defects in the post-test specimen, and AE data were correlated to the damage events.