Study of FRP bars under tension using acoustic emission detection technique

Acoustic emission (AE) signal has proved to be a useful tool for monitoring structures reinforced with FRP composites such as Fiber Reinforced Polymer (FRP) reinforced beams, carbon FRP (CFRP) sheets, or steel fiber reinforced concrete. This work focuses on studying the behavior of pultruded FRP bars, which have been manufactured using continuous fibers. Different configurations of CFRP and glass FRP (GFRP) bar specimens subjected to tensile load were monitored using AE technique. Several algorithms were used for signal processing to analyze AE signals in the time domain and in the time–frequency domain. The signal processing techniques extracted the amplitude, cumulative events, duration, energy, rise time, number of counts, cumulative counts, and frequency peaks of the acoustic signals. The frequency maxima were determined for different amplitude signals using short-time Fourier transform (STFT). Cumulative counts of AE signals showed significant changes in the slope during the tension test, while the stress–strain relationship of the FRP rods showed virtually no deviation from linearity. CFRP bars recorded higher amplitude signals and lower duration, than GFRP bars. The acoustic emission characteristics presented in this work show strong correlations with ultimate load and may prove useful for damage prediction.