Preliminary applications of acoustic emission detection systems on composite structures
Year: 2025
Type: article
Abstract: Acoustic emission (AE) is a phenomenon that follows the initiation of a crack in structural materials, i.e. after a loading sequence particularly intense. This phenomenon is strictly related to fatigue, intended as the creation of microcracks that, bit by bit, threaten the material and therefore the structural resistance. Since 1950, this crack generation has been demonstrated to be linked to acoustic waves travelling in the material. Therefore, AE shall not be confounded with sound emission. The research aims at detecting this kind of waves directly in the material and not after the very high frequency waves they can produce in the air, with the related losses in terms of travelling energy, eventually too small to be easily detected. The sensors that aim at detecting these waves, are called Acoustic Sensors, and shall not be confused with microphones, aiming at detecting sound pressure, travelling in the air. AE is currently getting new attention from the scientific and technological community for a number of applications that need a prompt identification of the health status of a certain structure. For instance, they allow getting info on the released energy after a crack event, making it possible to extrapolate indications on its residual life and support other structural health monitoring (SHM), systems to identify maps of the existing, current damage easily. Such potentialities are particularly interesting for critical structures, like the hydrogen tanks, recently recognized as a novel component on-board commercial aircraft, following the greening wave that is investing all the means of transport, and even all-day life. In this perspective, the widely used piezoelectric ceramics, excellent for their very large bandwidth, are hard to use for the possibility of spark insurgence after being exposed to strain fields. In this view, optical sensors could be a viable means for overcoming those limitations. Within the H2ELIOS, an EU Clean Aviation Project, CIRA is starting to develop its expertise, with the support of the consortium, to deploy a suitable AE sensor network for SHM purposes. In this activity, preliminary results are shown, mainly dealing with the characterization of typical crack signals by a common piezoelectric sensors network for individuating its main features, in view of replacing it with an optical acoustic system. Different coupons have been tested on a standard mechanical rig. At first, a simple growing damage was imposed, and the strain history was recorded and post-processed in detail, highlighting some peculiar properties of the acquired signal. In a second case, the signals were detected at the event insurgence, irrespective of the magnitude and variability of the quasi-static load therein applied, in the perspective of a full real-time application. A correlation analysis was then performed among the successive acquisitions, and some preliminary conclusions were drafted. Preliminary evidence of the equivalence between optical and piezoelectric systems was explored.
Source: Smart Materials and Structures
Institution: Italian Aerospace Research Centre
Language: English
Subfield: Mechanics of Materials
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,325
Funder: Clean Aviation
Award: G1396919804
OpenAlex ID: W4414192767