Micromechanical damage detection in fibre reinforced materials using ultrasonic birefringence

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In this project we intend to develop the ultrasonic birefringence method as a nondestructive testing method to detect damage and chances in the material structure of fiber reinforced materials. For this purpose we damage CFRP materials with a systematic damage degree to generate debonding of fibers and matrix, macroscopic delaminations and the generation of micro cracks. We detect this different types of damage by using ultrasonic birefringence. By using a new developed model for the birefringence effect we can calculate from the ultrasonic results the elastic constants G13 and G23. This findings is then transferred to a micromechanical simulation, to model the part behavior under different load profiles. In doing so we can correlate the influence of the micro cracks on the elastic constants and the corresponding mechanical properties of the CFRP reference samples. To solve the kind of inverse problem, we first have to solve the straight forward problem by using both standard FEM packages and new developed model of the birefringence. Here the reflection and scattering effects in different layers of the ply has to be taken into consideration. The objective of the project is the development of a new testing method to ensure a fast decision whether a component can be further operated or must be replaced within a certain time period.