PhD Progress Seminar - Elli Bellou

In the past years, 2D materials are a pole of interest for numerous applications, owing to their unique optoelectronic and mechanical properties. However, these properties can be affected by the presence of defects, which can be either inherently present or externally induced. In regard to the mechanical properties, defects act as regions of increased stress concentration which can ultimately lead to the fracture of the material. Therefore, the study of both the stress distribution at the vicinity of a defect (such as a hole, notch, or crack) and the fracture toughness of a material are important to predict its failure. In this study, graphene is produced either by chemical vapor deposition (CVD) or by mechanical exfoliation.  Firstly, Raman spectroscopy combined with in-situ tensile testing is adopted to assess the stress concentration in a CVD graphene-polymer model composite containing a circular hole. Also, the fracture toughness of CVD graphene/PMMA nanolaminates, which bear similar defects, is investigated using micro-tensile testing. Lastly, Atomic Force Microscopy is used to examine the stress-induced change in morphology (such as wrinkling or cracking) of defected graphene, which is obtained by mechanical exfoliation.