Composite materials have been widely employed by land transport, aerospace and marine structures as they offer many advantages over metals. However, with this increased use comes a greater need for Structural Health Monitoring (SHM), which can prove difficult for aerospace applications due to the high number of training experiments required for successful fault detection, identification, and localisation.
In order to circumvent this problem, TWI investigated the use of a finite element-based model to simulate these experiments. This provided an accurate replication of the vibration characteristics of both healthy and damaged structures. This modelling also allowed for an insight into the scalability of the results for real-world damage detection and characterisation.
The testing saw the manufacture of 40 carbon fibre / epoxy beams that were then subjected to impact tests with three different energies (5, 10, 15 joules) in three specimens. Infrared Thermography was used to assess the beams both before and after impact, which showed that the impacts had led to delamination.
These tests allowed for the development of an in-flight SHM platform for aerostructures based on a small number of vibration sensors. These sensors are able to provide a positive identification of impact damage as well as locating the damaged area.
Actual aircraft booms confirmed the success of determining damage in real parts and a prototype data acquisition and graphical user interface ensured that engineers would be able to assess the health of aerospace structures in real-time.
As a result of this work, vibration-based SHM methods should be able to provide an assessment of similar structures for both damage detection and localisation.
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