AVS 58th Annual International Symposium and Exhibition
    Advanced Surface Engineering Division Thursday Sessions
       Session SE-ThM

Invited Paper SE-ThM2
Tensile Testing of Substrate for Fracture Toughness of Thin Films

Thursday, November 3, 2011, 8:20 am, Room 104

Session: Nanostructured Thin Films and Coatings
Presenter: Sam Zhang, Nanyang Technological University, Singapore
Authors: S. Zhang, Nanyang Technological University, Singapore
X. Zhang, Nanyang Technological University, Singapore
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Measurement of fracture toughness for bulk materials is a routine but extremely difficult and still not standardized for thin films (or coatings). The difficulties in clamping a freestanding thin film and the requirement of a critical dedicate loading system are the main obstacles. In this talk, a method is proposed to carry out tensile loading of the substrate to avoid both problems. The film is deposited on a rectangular silicon wafer on which an edge crack is fabricated beforehand. The film is then “micromachined” into microbridges perpendicular to and ahead of the initial substrate crack. A displacement controlled tensile force is applied to propagate the substrate crack and fracture the "microbridges". The critical fracture strain of the microbridge is measured through measuring the strain of the substrate at the respective location of the microbridge. The fracture toughness of the film is thus obtained in between the un-fractured and the last fractured bridge. A case study is also presented.