Non-contact femtosecond laser-based methods for investigating glass mechanics at small scales

With the progress made in miniaturizing systems over the last decades, understanding materials’ behavior at small scales has become a necessity. In this context, glass behavior has remained largely unknown, partly for technological reasons and partly due to the inherent difficulties associated with its brittle fracture behavior. Despite their importance for technological implementation, questions such as its failure statistics or its behavior under constant load remain unanswered. This thesis aims at filling the gap of the available methodologies and instrumentation for the mechanical testing of glass at the micro-/nano- scale. Until recently, suitable methods for manufacturing arbitrary shapes in glass were missing, hampering the implementation of appropriate testing methods. Fortunately, recent progress in the field of femtosecond laser processing has opened new opportunities for designing specific tools adapted to the investigation of glass micromechanics. In addition, the careful observation of nanoscale self-organization processes taking place during laser exposure offers a novel means for observing fracture statistical behavior. Here, we use this novel glass processing method to introduce two novel experimental approaches: one based on novel concept of contactless micro-/nano-monolithic tensile tester, and a second one, based on statistical observations of an intermittent behavior occurring during laser exposure. Using these two approaches, we are able not only to load the material to unprecedented high level of stress and this, in a pure tensile mode, but also to study stress relaxation effects and finally, to explore its fracture statistical behavior. From the technology development perspective, this thesis offers an experimental framework for contactless testing of glass materials that, in particular for silica, set guidelines for microsystems designers. In parallel, this work demonstrates the use of unconventional methods, inherited from other scientific disciplines, as a means for extracting relevant brittle fracture parameters, usually difficult to obtain at the microscale and requiring extensive numbers of experiments.

Bellouard, Yves
Lausanne, EPFL

 Record created 2018-04-03, last modified 2019-05-09

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