Micromechanical damage detection in fibre reinforced materials using ultrasonic birefringence

在这个项目中，我们打算发展超声波双折射方法作为一种无损检测方法来检测纤维增强材料材料结构中的损伤和机会。为此，我们对CFRP材料进行了系统性损伤，导致纤维和基质脱粘、宏观分层和微观裂纹的产生。我们使用超声双折射来检测这种不同类型的损伤。利用新发展的双折射效应模型，我们可以从超声结果中计算出弹性常数G13和G23。然后，这些研究结果被转移到微观机械模拟中，以模拟不同载荷分布下的零件行为。这样，我们就可以将微裂纹对CFRP参考样品的弹性常数和相应的力学性能的影响联系起来。要解决这类逆问题，首先必须用标准的有限元程序和新发展的双折射模型求解正解问题。这里必须考虑铺层不同层中的反射和散射效应。该项目的目标是开发一种新的测试方法，以确保快速决定部件是否可以在特定时间段内进一步操作或必须更换。

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.