This thesis deals with matrix-cracks in fiber reinforced plastics, their effect on strength and life expectancy as well as the nondestructive evaluation of the cracks. In most long fiber reinforced plastics inter-fiber-cracks occur at an early stage. About their formation, their growth and increase profound knowledge exists. The increase in crack density shows a typical chronological sequence. This can be used to represent the damage state by non-destructive test methods. One elegant and easy method for the monitoring of degradation is to directly evaluate the transparency of glass-fiber-reinforced-plastic-specimen. With Fatigue tests including this method it could be shown, that the evaluation of light transmission allows good conclusions about the damage state. This easy to handle method, however, is limited to transparent laminates in laboratory scale. Below a strategy is investigated, to transfer the advantages of direct evaluability and straightforwardness of this approach to other non-transparent laminates. An indicator layer of glass fiber fabric can make the crack density evolution in the course of material fatigue visible. The interaction between such layer and the base laminate is examined and it is found that the fine structure of the fabric layer plays an important role in the representation of cracks in the substrate by well-reflective micro-delaminations. Fatigue tests show comparable sequences of reflectivity. This encourages the use of this principle as a simple, straightforward structural health monitoring method. The results of the investigation suggest to further develop the use of a thin glass-fiber layer as a utilizable method for the early identification of crucial developments in inter-fiber failure. The uncomplicated principle allows examination of big surfaces and further evolution will allow automatic recording in difficult to access places as well as partly automated evaluation at low extra structural weight.


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    Title :

    Eine transparente Deckschicht als visueller Indikator für die Rissentwicklung in CFK


    Additional title:

    A transparent top-layer as visual indicator for crack development in CFRP


    Contributors:

    Publication date :

    2016



    Type of media :

    Miscellaneous


    Type of material :

    Electronic Resource


    Language :

    Unknown



    Classification :

    DDC:    387 / 620 / 542






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