Pushing the Limits of Acoustic Emission for the Benefit of Performance of Engineering Materials

Acoustic emission (AE) is used for characterization of materials condition. Detection of cracks, localization, fracture mode determination is conducted in laboratory conditions, while certain features are applicable in-situ. It is established that the dominant damage mechanism emits signals with distinguishable characteristics allowing its identification. This has been verified in all types of cementitious media (mortar, concrete, steel fiber- or textile- reinforced matrices) as well as in polymer composites and masonry. However, the sensitivity of AE allows conclusions earlier than the moment of damage manifestation and well before cracks become measurable in any way. Recently, AE was shown sensitive to the strain field, as this is expressed by the ratio between shear over normal strains in the material, allowing projections to the final damage. Results show repeatable, monotonic relations between AE parameters and strain field even at small fractions of the ultimate load. This contributes to the real-time assessment of the condition of the material, before the load-bearing capacity is compromised, while being also very promising for in-situ application. This study highlights the new trends showing the potential of using AE complemented with other techniques, like digital image correlation and ultrasound, to adequately monitor and predict the behavior of structural materials.