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Output-only modal-based structural health monitoring in composite beams

Ruben Teunis – University of Twente (December 2014 – August 2015)
Complete version


Composite materials are frequently used in airplanes and aviation applications, like helicopters. Damages in composite materials are in most cases complex and hard to detect. To obtain the real condition of the blades, structural health monitoring technology can be applied. In the way, the composite materials can be used more safely and effectively.

Figure 1: Picture of the experimental setup

Figure 2: Zoomed SolidWorks render of the test setup

Experimental work is performed on an in-house developed test setup, see figure 1 and 2. Point masses are added to simulate different damage cases. The modal strain energy damage index and modal curvature damage index are applied. Only the first method gave satisfying results. Two example cases are shown below. The arrow indicates the damage location.


  • A properly working test setup, showing a flapping motion, is obtained. (See figure 1 and 2)
  • Output blade vibrations are used to detect damage of several damage scenarios.
  • Single damages can be identified in all considered cases. (See figure 3)
  • Multiple damage cases were very hard to identify with the applied method. (See figure 4)

Figure 3: Example case for a single damage.

Figure 4: Example case for multiple damages.