Fatigue damage monitoring in carbon fiber reinforced polymers using the acousto‐ultrasonics technique

Abstract This study focuses on the nondestructive monitoring of damage developed in carbon fiber reinforced polymers during fatigue loading via in situ acousto‐ultrasonics (AU) measurements. Carbon nanotubes (CNTs) were used as modifiers of the epoxy matrix of quasi‐isotropic carbon fiber reinforced laminates and consequently two composite material systems (one with matrix doped with CNTs and one with nondoped matrix) were manufactured and tested. The AU technique is utilized toward the monitoring of damage development, evolution, and accumulation during the fatigue tests. The AU waveforms acquired are processed using conventional (both in time and in frequency domain) as well as innovative wavelet‐based signal processing techniques to extract parameters‐indicators capable of monitoring and quantifying the damage accumulation into the test coupons. Based on the analysis of AU monitored signals, critical descriptors (parameters) were identified that show significant variation and monotonic behavior throughoutthe tests and thus can be proposed as potential candidate parameters for monitoring the damage development in composite materials. POLYM. COMPOS., 31:1409–1417, 2010. © 2009 Society of Plastics Engineers