Dresden 2026 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 32: Topical Session: Advanced Nanomechanics – Accelerating Materials Physics from the Bottom I
MM 32.6: Talk
Thursday, March 12, 2026, 12:30–12:45, SCH/A251
The Fracture toughness of thin films — •Mathias Göken1, Benoit Merle2, and Jun Lou3 — 1Department of Materials Science & Engineering I, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany — 2Materials Science and Engineering, Universität Kassel, Germany — 3Department of Materials Science and NanoEngineering, Rice University, Houston, Texas, USA
The mechanical properties of thin films play a pivotal role for applications either as freestanding films or as coatings. So far, the understanding of the fracture toughness of very thin films and especially of their thickness dependence is limited. Bulge testing is a very reliable technique for characterizing the mechanical properties of thin films, where a freestanding film is subjected to a controlled pressure from underneath and the deflection of the film is recorded. Bulge tests have shown that the fracture toughness of ductile and soft Au drops down to extremely low values of only 2 MPam1/2 if the film thickness is reduced to 100 nm. On the other hand, single layer graphene has shown a fracture toughness of around 4 MPam1/2. In this paper the thickness dependence of the fracture toughness is discussed based on an old and simple basic fracture mechanics concept derived by Bluhm and Knott in the 1960th. It is shown, that based on this model it is easy to predict the fracture toughness of thin films and their thickness dependence. The results agree surprisingly well with the experimental data on graphene and Au thin films.
Keywords: graphene; fracture toughness; bulge test; nanomechanics; thin films