Peak frequency analysis via wavelet transform for impact damage mechanisms in woven composites

Abstract

Impact damages have been a major concern in the design of laminated composite structures since the damages mainly occur within the materials in a very short time. In this article, impact induced damage mechanisms of woven composites were investigated by means of novel SHPB-AE coupled tests. A step-consisting new methodology was developed; first, damage mechanisms of woven composites were determined by peak frequency analysis via wavelet transform (WT); second, the extraction of a range of acoustic emission (AE) parameters was achieved from AE energy, duration, and amplitude on the basis of peak frequency analysis; finally, the quantification of damage mechanisms was accomplished through a normalized cumulative AE count. In order to confirm the features of damage, the microscopic characterization of damage mechanisms was performed for the materials. As a result, the determination of impact damage mechanisms in tested composite materials was possible by peak frequency analysis via WT along with waveform and intensity examinations. In addition, the mechanisms could be identified by confirming the progress-based distribution and band formation of peak frequencies. AE parameter ranges were also extracted in terms of amplitude, duration, and energy according to the damage mechanisms. The damage process of the woven composites under impact loading began in the matrix and immediately caused fiber breakage to occur. Subsequently, multiple damage mechanisms were shown, such as fiber-matrix debonding, fiber pull-out, severe deformation and rupture in Kevlar fiber tips. The proposed methodology for the novel SHPB-AE coupled test of woven composites therefore showed an effective way to figure out in situ information on the damage under impact loading.