Composite Materials Research Progress

216
W. Van Paepegem, I. De Baere, E. Lamkanfi et al.
composite specimen. The frequency inverter reads the signal from the rotary encoder and can
stop and hold the motor at a predetermined angular position of the encoder.
Figure 7. Test set-up for cantilever bending fatigue [28].
A digital photograph of the out-of-plane displacement profile is taken from the side view.
To enhance the contrast, the edge of the composite specimen has been painted white. An
example of such a digital photograph is given in Figure 8. When the number of pixels for a
known distance is counted, the out-of-plane displacement profile can be calculated. Thereto
an edge-detection algorithm is used which detects the edges of the composite specimen on the
digital photograph. Figure 8(right) shows an example of the edge detection algorithm. Of
course, the calculated out-of-plane displacement profile applies to the deformation of the
specimen surface, not to the out-of-plane displacement of the midplane of the laminate.
Figure 8. Use of image processing algorithms to track the out-of-plane displacement profile in
cantilever bending fatigue.