Concept and Objectives:

The safe use of complex engineering structures such as aircrafts can only be guaranteed when efficient means of damage assessment are in place. Whereas the design of civil structures is nowadays based on a damage tolerance approach and time based inspection cycles, it is envisaged that the large cost associated with this approach can be drastically reduced by switching to a condition based maintenance schedule. Structural health monitoring is a technology where integrated sensors are used to enable continuous monitoring of the structural integrity.

In the last years there is an increasing interest in structural health monitoring systems for aircraft. Beside the expected enhancement of safety and maintenance performance, also economic aspects play an important role. This regards on the one hand the reduction of unnecessary inspection costs and on the other hand, the possible weight reduction of aircraft part at the designing phase of an aircraft. This project wants to continue the project “Aircraft Integrated Structural Health Assessment (AISHA) EU-FP6, priority 4 – STREP project nr. 502907) which was dedicated to the establishment of the basic elements of a health monitoring systems based on ultrasonic Lamb waves.

Lamb waves are guided waves propagating in plate-like structures. Experiments on lab-scale and on selected full-scale parts showed the ability of Lamb-waves to give indications of correlations between acoustic parameters and damage in structural parts. The consortium is aware of the fact that a 42-month project is not sufficient to make the final step for a ready-to-use system. Thus, based on the rich experiences obtained in the running AISHA project which will be finished in June 2007, we want propose a new project with an adapted work plan and additional new partners.

AISHA II Results in brief:

Sensing danger before it strikes

The aerospace sector is committed to reducing costs and enhancing safety. Novel sensor technology for continuous monitoring of structural integrity is making both of these goals possible.

Structural health monitoring (SHM) refers to technologies used to continuously assess the structural integrity of components and systems using integrated sensors. Rather than conduct arbitrarily timed inspections, this condition-based maintenance approach can significantly reduce costs and enhance safety.

SHM has become an important area of research and development in the aerospace sector. The Sixth Framework Programme (FP6) project ‘Aircraft integrated structural health assessment’ (AISHA) established the basic elements of an ultrasonic Lamb wave-based SHM system. To overcome challenges around signal interpretation and durable sensor connections, another EU-funded project called ‘Aircraft integrated structural health assessment II’ (AISHA II) was initiated.

Scientists introduced new methods like percolation conductivity, ultrasonic time-of-arrival methods, non-linear ultrasound, pseudo-defects and electrochemical impedance spectroscopy. A partnership with leading maintenance company made it possible to equip three operational airliners with percolation sensors.

At the International Workshop of Structural Health Monitoring at the University of Stanford, this improved technology earned the ‘Most practical SHM application in aerospace’ award.

AISHA II successfully delivered novel SHM technology for the aerospace community and beyond. Commercialisation will have important impacts on aerospace safety, costs and competitiveness, with applications for other fields also expected.

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