Mechanical Response of a Glass

Because of their disordered structure, the glasses are expected to have a very different mechanical response from that of a crystal. For the latter, the elastic response is controlled by the vibrational properties of the crystal and the plastic response is understood by the presence of defects in the crystal structure.

On the one hand, we have probed the response to pure static shear of a granular glass close to jamming. The shear strain is induced by the inflation of an intruder at the center of the packing. On the other hand we have characterized the intermittent dynamics of an intruder pulled within the glass at constant force. In the first case, it was impossible to achieve a linear regime. However small is the deformations we could impose, the mechanical response of the glass was weaker than elastic : one speaks of "shear softening". In the second case we have shown that the very intermittent dynamics of the intruder proceeds by successive avalanches from which we have extracted the statistical characteristics.

We are currently developing a device that will allow us to probe the entire response range, elastic if it exists to plastic.

Coulais, C., Seguin, A., & Dauchot, O. (2014). Shear Modulus and Dilatancy Softening in Granular Packings above Jamming. Prl, 113(19), 198001.

Candelier, R., & Dauchot, O. (2009). Creep Motion of an Intruder within a Granular Glass Close to Jamming. Physical Review Letters, 103(12).