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The fatigue behaviour of quasi-isotropic carbon fibre reinforced epoxy laminates under tension-tension cyclic loading is investigated. The acoustic emission technique is used to monitor the different damage mechanisms activated throughout the fatigue life. Filtering of acoustic emission events is performed to reject the events attributed to friction related mechanisms. After appropriate filtering of the AE data, the fatigue damage process can be monitored in terms of cumulative AE counts. [ABSTRACT FROM PUBLISHER]

Abstract: Acoustic emission (AE) is a useful non-destructive technique to determine whether damage in rock material has occurred, even though the interpretation of AE can be complex. In this paper, two laboratory situations are studied, to investigate the correlation between micro-fractures and AE. In the first case, damage is induced by pure macro-compressive stresses and in the second case by macro-tensile stress (in one direction). The specific evolution of the recorded cumulative AE energy as a function of the applied load leads, in both cases, to a subdivision of the loading in different phases. Thresholds for the transition of these phases are defined. A thorough petrographical analysis of thin slices of samples, damaged to these different thresholds, allows a physical interpretation of damage phases. This methodology leads to a damage evolution model both for macro-compressive and macro-tensile stresses. This paper demonstrates the advantages of the combined use of AE and detailed petrographic study of thin rock slices. Furthermore, insight is provided on the pre-peak damage evolution caused by macro-compressive and macro-tensile stresses in rock material. [Copyright &y& Elsevier]

Sensitivity of the Kaiser effect to the deviations of the directions of σ1-principal stress experienced by rock in successive loading cycles has an important impact on the application of this effect for stress measurements in rocks. The paper presents an analysis of the gradual Kaiser effect degradation with increasing deviation of the principal stress axes between loading cycles in Brazilian experiments. An experimental study was carried out to investigate the Kaiser effect in cyclic loading tests of disk specimens of a brittle limestone in diametrical compression with acoustic emission measurement. Tests were performed in which disks were loaded in two cycles without or with rotations between successive cycles. The rotation angle varied between 0° and 90°. The Kaiser effect became gradually less pronounced with increasing rotation angle, but remained detectable for angles <10°. Rotation by more than 10° resulted in complete disappearance of the effect. These experimental results were confirmed by numerical simulations using the displacement discontinuity method. [Copyright &y& Elsevier]

• AE fracture mode characterization of masonry constituents. • Successful correlation between full-field strain pattern from DIC with AE indices in masonry components. • Shear fracture mode characterization. • FEM numerical simulation. In this paper, an experimental study conducted on Red Clay brick masonry "triplets" built with Cement and Lime-based mortars is presented. Monitoring of fracture is executed by Acoustic Emission (AE) and Digital Image Correlation (DIC). First, for a profound understanding of individual properties, small scale experiments were conducted for characterization of AE signatures of mortar and brick separately. Representative masonry triplet elements are tested in shear for investigation of the fracture mechanisms in relation to the properties of different mortars. Localization of the cracks as well as source identification is performed by means of AE parameter-based analysis. Their correlation with DIC, accurately showed the location of macro cracking and the developing of strain concentrations even before fracture. This is one of the first investigations where full field strain pattern from DIC are successfully correlated with AE indices in masonry. Numerical simulations were also performed for validation and prediction purposes. [ABSTRACT FROM AUTHOR]