The project “Non‑invasive acoustic Structural Health Monitoring System for PUR‑based coating systems” was carried out within the MegaYachtSchaum consortium (FKZ 03SX440E) from 1 January 2019 to 30 September 2022. The consortium was funded by the German Federal Ministry of Education and Research and included the Institute for Sensor and Actuator Technology (ISAT) at the Hochschule Coburg as the lead partner, together with several other academic and industrial collaborators. Prof. Dr. Klaus Stefan Drese served as project leader. The final report was issued on 27 March 2023 and documents the technical achievements and the collaborative framework of the effort.
The core objective of the sub‑project was to develop a robust, non‑destructive, online‑capable Structural Health Monitoring (SHM) system that can be applied to large areas of a ship hull. The system is specifically adapted to the sprayable hard polyurethane (PUR) foam coating that is used in the MegaYachtSchaum programme. Guided acoustic waves – a specialised form of ultrasound that propagates along the hull surface – were chosen as the sensing modality because of their sensitivity to changes in material thickness, stiffness and the presence of fluids. Sensors were mounted on critical internal hull locations to monitor, in real time, the separation of the hard foam layer from the steel substrate and the ingress of water. In parallel, the project investigated whether the same acoustic technique could detect hair‑line cracks in the outer paint, delamination of the PUR foam from the deck laminate, and the presence of air pockets within the deck laminate. The ultimate goal was to provide a quasi‑continuous, high‑resolution monitoring solution that would enable early detection of damage and thereby support quality assurance during operation at sea.
During the three‑year period the team designed and fabricated a sensor array that integrates piezoelectric transducers with a custom signal‑processing chain. The array was calibrated on laboratory specimens that mimicked the ship‑hull geometry and the PUR coating. The final results section of the report presents quantitative performance data: detection sensitivity, spatial resolution, and false‑alarm rates for each damage mode. While the exact numerical values are not reproduced here, the report confirms that the system can reliably identify delamination and water ingress at distances of several centimetres from the sensor, and that it can resolve hair‑line cracks on the outer paint layer with a spatial resolution better than 5 mm. The acoustic signatures of air pockets in the deck laminate were also successfully distinguished from other defects, demonstrating the versatility of the guided‑wave approach.
The collaborative effort was structured around regular workshops and data‑exchange sessions. ISAT provided the core expertise in guided acoustic wave physics and sensor fabrication, while partner institutions contributed test vessels, industrial‑scale coating facilities, and expertise in maritime structural analysis. The consortium’s joint milestones were tracked against the project schedule, and the final report documents that all deliverables were met within the allocated timeframe. The funding from the BMBF covered research and development costs, equipment procurement, and personnel expenses. The consortium plans to further develop the technology for deployment on commercial vessels, and the report outlines a strategy for transferring the system to industry partners, including plans for standardisation and integration into existing ship‑maintenance workflows.