Characterization of mechanical performance of concrete beams with external reinforcement by acoustic emission and digital image correlation

Characterization of the damage mechanisms of a structure in real time is a challenging engineering task. Several nondestructive testing techniques have been used according to their capabilities and the target problem. Acoustic emission (AE) is one of them, enabling to record the elastic waves due to propagating cracks and to evaluate the criticality of the condition. Information on the location of the cracking sources, their mode and severity can be supplied by proper analysis of AE parameters and trends. However, in certain cases assumptions are inevitable and many times the experience of the user is essential in order to explain the AE trends according to the actual damage mechanism occurring at the moments when AE changes are registered. In the present case AE is used for monitoring the bending failure of concrete beams reinforced by external layers of different composite materials. The monitoring is complemented by Digital Image Correlation (DIC) which gives a clear depiction of the surface strain field and its transient changes according to stress redistribution which occurs after fracture moments. Results of AE are thus benchmarked and certain trends reliably attributed to specific processes. Conclusions on the mechanical performance of the different reinforcing materials on the beams, which is another major aim of the study, are also drawn.