I am now a post-doc at MIT. Check my new website.
jmarthel A_T mit.edu
Research interest while at SVI, Saint-Gobain - CNRS and PMMH, ESPCI Paris
Cooperation fracture-delamination : spiral and croissant cracks paths in thin films
Thin film are widely used to functionalize surfaces. During the deposition process, the film usually build residual stresses that could cause the failure of the film by fracture or delamination. We study a new way of crack propagation where delamination and fracture cooperate leading to the failure of films usually considered as stable. The robusteness of the crescent and spirals patterns offer new opportunities to use cracks as a tool to pattern surfaces at small scales.
See also movies of fracture in real time of a crescent alley, a spiral or a competition between a duo of cracks and a following crack.
Self-replicating cracks: A collaborative fracture mode in thin films Phys. Rev. Lett 113, 085502. 2014
Thin film stability on flexible substrate : fracture
Mechanics of stiff coating film deposited on soft plastic substrates have recently gain interest due to the development of stretchable electronics application. When submitted to tensile stress, such films tend to fail with the apparition of arrays of parallel channel cracks transverse to the direction of deformation, with fatal consequenses for electrical conductivity. We study the propagation of such fractures in oxyde monolayers coated on a polymer substrate under uniaxial stretching. We show how the crack density undergoes a transition from a statistic failure distribution of brittle material to a deterministic failure set by the elastic mismatch between the film and the substrate and the substrate ductility.
Thin film stability on flexible substrate : wrinkling and buckling
The mismatch of Poisson ratio between the layer and the substrate lead to compressive strain in the transverse direction. For increasing applied strain, we observe undulations, wrinkles and delamination blisters. We study the interface strengthening by plastic dissipation in multilayer sandwich silver layer.
Janssen effect and gravity driven discharge in a soft silo
with Thomas Cambau and Jérémy Hure
In 1895, Janssen quantified the saturation of the bottom pressure in a granular material contained in a vertical container. He defined a typical pressure saturation length, accounting for friction of the grains on the container’s wall. The practical interest in avoiding the damage and collapse of silos has motivated numerous studies. In those studies, stresses were inferred from the measurement of the apparent mass at the bottom of the column. We directly obtained the stress field all along the column by measuring the displacement field of a soft elastomer silo containing a granular column. We confirmed the validity of Janssen’s description and determine the stress field during the gravity driven discharge of a silo through an aperture.
A new failure mechanism in thin film by collaborative
fracture and delamination: interacting duos of cracks (pdf)
J. Marthelot, J. Bico, F. Melo and B. Roman, JMPS 84, 214–229, 2015
Self-replicating cracks: A collaborative fracture mode in thin films (pdf)
J. Marthelot, B. Roman, J. Bico, J. Teisseire, D. Dalmas and F. Melo, Phys. Rev. Lett 113, 085502, 2014
Local stresses in the Janssen granular column (pdf)
T. Cambau, J.Hure, and J. Marthelot, Phys. Rev. E, 88, 022204, 2013
Rotational dynamics of a soft filament : wrapping transition and propulsive forces (pdf)
N. Coq, O. du Roure, J. Marthelot, D. Bartolo and M. Fermigier, Phys. Fluids., 20, 051703, 2008.
Rupture et délamination de films minces (en français) (pdf)
Thèse de doctorat de l’Université Pierre et Marie Curie, soutenue le 18 juin 2014.