Acoustic emission characterization of damage sources of lightweight hybrid concrete beams

Lightweight hybrid concrete beams are advantageous in terms of installation, but their mechanical behaviour is not easy to predict due to their heterogeneity. In the present study composite hollow beams made of Textile Reinforced Cement (TRC) reinforced with Carbon Fibre Reinforced Polymer (CFRP) strips and a concrete layer are subjected to bending. Their fracture behaviour is complicated as they exhibit multiple failure mechanisms: cracking of the cement matrix, debonding of the CFRP and delamination between successive layers of TRC. Herein, their mechanical performance is evaluated and monitored by Acoustic Emission (AE) and Digital Image Correlation (DIC). AE indices show that beams suffering from one major failure mechanism (matrix cracking) release AE signals with high frequency content while beams suffering from delaminations exhibit longer AE waveforms of lower frequency. These tendencies are obvious even at early loading stage, enabling prediction of the mode of the subsequent failure.