Innovation Coffee

The opening scene of the animated film Ice Age provides an extreme example of brittle fracture: the sabre-toothed squirrel's attempt to bury an acorn triggers an ever-widening crack that ends up splitting the entire iceberg. However, there is a grain of truth in this dramatically exaggerated movie scene, namely the fundamental properties of these brittle materials such as glass or ceramics. A breakage is almost always triggered by small “defects” (pores, cracks, inclusions, etc.) that can hardly be avoided during production.

This problem can have dramatic consequences for technical components. If, for example, a ceramic mirror holder in a satellite breaks under the stress of a rocket launch because such a defect was found at a critical point, this means a loss running into the millions. Until now, to remedy the situation, complex mechanical tests (proof tests) had to be carried out on each individual component in order to detect faulty components before they were used.

In recent years, the Fraunhofer Center for High Temperature Lightweight Design HTL has developed cheaper alternatives to this. The basis in each case is an imaging process such as computer tomography (for volume defects) or laser scanning microscopy (for surface defects). The relevant inhomogeneities/defects are extracted automatically, in some cases with appropriately trained AI algorithms, and their individual influence on fracture behavior is evaluated with the help of FE simulations. The resulting classification of defects with regard to their effects on the fracture strength of a material can be used for targeted material development in the field of brittle materials such as ceramics of all kinds. Another exciting area of application for these non-destructive test methods is to use them as a fast and cost-effective replacement for proof tests. The basic feasibility has already been demonstrated in a project commissioned by the ESA.

The presentation will give an overview of how the methods work and what advantages they offer in application either as an alternative to - or in combination with - classic mechanical testing methods.