8 – Acoustic emission in delamination investigation

Publisher Summary Acoustic Emission [“AE―] testing is based on analyzing acoustic waves caused by rapid stress changes in many materials. As a highly sensitive, quasi-nondestructive test method, AE has been successfully applied to in-service inspection, integrity and proof testing of components and structures, as well as materials characterization. AE requires only a limited number of surface mounted sensors for volumetric monitoring. In Fiber-Reinforced, Polymer-matrix [“FRP―] composites stable propagation or unstable growth of delaminations are the important macroscopic mechanisms which lead to damage and reduce the strength of FRP composites. Delamination propagation or growth involve a large number of microscopic damage events such as intra- or inter-ply matrix cracking, fiber breakage, and secondary effects such as rubbing between surfaces. All these mechanisms cause AE. In structures manufactured from FRP composite materials, impact is one of the main causes for delaminations. Impact damage inside may be much more severe than its appearance on the surface, and detecting delaminations is hence crucial for ensuring safe operation or use of FRP composite elements and structures. AE has been shown to be a useful method for detection of damage accumulation in FRP composites.