3:30–4:30 pm Maria Goeppert-Mayer Lecture Hall, KPTC 106
Fractured Flows
Irmgard Bischofberger, MIT
Faculty Host: Sidney Nagel
Particle suspensions can fracture into intricate patterns when driven out of equilibrium. We investigate fracture and relaxation in dense aqueous cornstarch suspensions exhibiting discontinuous shear-thickening behavior. Air injection into three-dimensional bulk suspensions can lead to smooth bubbles that rise upwards under the action of buoyancy or to sharp fractures that remain attached to the injection nozzle. We relate the shape and the relaxation dynamics of the air cavity to the suspension rheology. As bubbles reach the free surface, they exhibit distinct bursting modes, suggesting that their rupture dynamics may provide a probe of the rheology of thin suspension films. In a second example, we discuss the crack dynamics and morphology occurring as drops of aqueous nanoparticle suspensions evaporate on a glass substrate and leave behind a solid particle deposit. Stresses in the deposit generated during the final drying stage are relieved through two distinct mechanisms: out-of-plane bending of the deposit or the formation of a secondary generation of cracks.