Several types of flaw can occur during the layup process of prepreg composite laminates. Quality control after the production process checks the end product by testing the specimens for flaws which are included during the layup process or curing process, however by then these flaws are already irreversibly embedded in the laminate. This paper demonstrates the use of a laser displacement sensor technique applied during the layup process of prepreg laminates for in-situ flaw detection, for typical flaws that can occur during the composite production process. An incorrect number of layers and fibre wrinkling are dominant flaws during the process of layup. These and other dominant flaws have been modeled to determine the requirements for an in-situ monitoring during the layup process of prepreg laminates.
This paper demonstrates that existing Structural Health Monitoring (SHM) techniques have potential during the
production phase in addition to their application for maintenance and for in-flight monitoring. Flaws occur during
composite fabrication in industry, due to an imperfect process control and human errors. This decreases production
efficiency and increases costs. In this paper, the monitoring of Lamb waves in unidirectional carbon fibre (UD-CFRP)
prepreg material is demonstrated using both Fibre Bragg Gratings (FBG)s and piezolectric acoustic sensors, and that
these SHM sensors may be used for flaw detection and production monitoring. The detection of Lamb waves in a one ply
thick sheet of prepreg UD-CFRP material is demonstrated for an FBG sensor aligned with the carbon fibre orientation
and bonded to the surface of the prepreg, Furthermore, the velocity of Lamb waves in prepreg UD-CFRP in different
orientations is investigated. Finally the successful detection of a material crack in a prepreg UD-CFRP sheet using the
Lamb wave detection method is demonstrated.
Research on extrasolar planets is one of the most rapidly advancing fields of astrophysics. In just over a decade
since the discovery of the first extra-solar planet orbiting around 51 Pegasi, 289 extrasolar planets have been
discovered. This breakthrough is the result of the development of a wide range of new observational techniques
and facilities for the detection and characterisation of extrasolar planets. In Utrecht we are building the Extreme
Polarimeter (ExPo) to image extra-solar planets and circumstellar environments using polarimetry at contrast
ratio of 10-9.
To test and calibrate ExPo, we have built a laboratory-based simulator that mimics a star with a Jupiter-like
exoplanet as seen by the 4.2m William Herschel Telescope. The star and planet are simulated using two single-mode
fibres in close proximity that are fed with a broadband arc lamp with a contrast ratio down to 10-9. The
planet is partially linearly polarized. The telescope is simulated with two lenses, and seeing can be included
with a rotating glass plate covered with hairspray. In this paper we present the scientific requirements and the