Aircraft maintenance involves periodic inspections after a certain number of flights or amount of time. Airframe structures are generally made damage tolerant by means of redundant (fail-safe) designs for which the inspection intervals are set to provide at least two inspection opportunities in the number of fights it would take for a visually detectable crack to grow large enough to cause a failure in flight. You can find detailed information about our research related to this theme in our Green Aviation Booklet.
Damage tolerant structures
Research at Imperial has developed improved models for predicting the behaviour of flaws in aircraft structures (both metallic and composite) and by incorporating variability data, the probablity of failure can also be accurately estimated.
Runway stones thrown up by aircraft tyres can lead to considerable damage to aircraft structures and so is an important consideration in the design of a damage tolerant airframes, yet until recently there was limited understanding of the stone lofting mechanisms. Research in the Department of Aeronautics has identified these mechanisms and developed a model which enables quantification of the impact threat from runway debris.
Morphing and adaptive concepts to allow large shape changes are increasingly being investigated for aerodynamics improvements. They can also reduce maintenance costs as with fewer parts inspections are much easier. One concept being investigated by our researchers has utilised carbon fibre/polyurethane composite to fabricate a corrugated morphing wing. The aim is to optimise the shape and geometry of the corrugated skin such that the lift to drag ratio of the morphing wing is maximised.
Structural health monitoring
Senorised structures for the purpose of damage detection is of growing interest. Researchers in the Department of Aeronautics have been developing computational tools to model structural health monitoring systems and these tools are being used to predict the effectiveness of the system in detecting damage (e.g. due to impact) and to optimise the positioning of the sensors in the system.