Digital image correlation (DIC) allows 2D mapping of the deformations occurring in a material, by tracking the displacements of a speckle pattern deposited on the specimen surface. The spatial resolution of the strain fields calculated with DIC depends on that of the speckle, and good-quality nanometric patterns are particularly challenging to obtain. By relying on the e-beam evaporation of indium, which has the ability to form discontinuous “islands” onto the substrate material, ultra-fine speckle patterns were successfully deposited in Winfab onto carbon and glass fibre reinforced polymer composite surfaces. In-situ compression testing of the speckled specimens was performed in a SEM in Lacami, and the acquired images enabled the first nanoscale DIC measurements on this type of material. This new method will hopefully help shed light on the local deformation and fracture behaviour of composites at the fibre scale, which is crucial for designing accurate finite element models of these materials throughout the lengthscales.
This achievement was made possible by the team work of two IMAP PhD students, Nathan Klavzer and Sarah Gayot (supervisor : Pr Thomas Pardoen), and a Senior Researcher, Michaël Coulombier. This work was recently presented at the European Solid Mechanics Conference (ESMC) in Galway, Ireland, and received the Euromech Young Researcher Award among 500 candidates.
Photo : Pr. Peter McHugh (president de ESMC 2022), Sarah Gayot and Pr Marc Geers, president d’Euromech (société européenne de mécanique).