Detecting and fixing aircraft defects in situ

Typically, more than 30 % of an aircraft's average life-cycle cost is due to inspection and repair. This does not include lost profits during grounding for scheduled replacements of parts, with profit losses around EUR 250 000 per day for a grounded commercial plane.

Scientists are developing state-of-the-art non-destructive inspection technology and new self-healing materials with EU funding of the project ALAMSA (A life-cycle autonomous modular system for aircraft material state evaluation and restoring system). Continuous monitoring of structural integrity in situ will enable self-repair at an early stage, minimising lost hours on the ground. The innovations support smart aircraft maintenance and an important step on the path toward maintenance-free planes.

The non-destructive monitoring exploits cutting-edge non-linear elastic wave spectroscopy techniques, an innovative class of vibro-acousto-ultrasound techniques. They have higher sensitivity and the ability to image internal areas not accessible with conventional methods. Further, they are able to detect a variety of defects in structural integrity, including microcracks, delaminations and adhesive bond weakening. Several different types of non-linear imaging methods (surface or subsurface imaging, tomography and time reversal) were developed, improved and tested on a variety of composite samples and components.

Self-healing capabilities focus on thermally activated materials and magnetically activated ones. The intrinsic self-healing (thermally activated) materials were obtained by inclusion of liquid healing agents in a compartmented thermoset polymer matrix. They promise the ability to restore mechanical properties more than once through reversible processes. The extrinsic self-healing materials consist of magnetic nano- and/or microparticles embedded in a thermoplastic polymer stabilised by ionic cross-linkages (ionomer).

Numerous models are supporting development of the innovative technologies. They will be a lasting legacy for future projects, providing important insight into non-linear interaction of waves with defects for aviation applications and composites in general. The project has been widely publicised via a strong presence at numerous international conferences and exhibitions as well as publications in peer-reviewed scientific journals.

Quality control, inspection and maintenance technologies under development within the ALAMSA project will increase the competitiveness of Europe's aerospace industry while enhancing the safety of its passengers.