research

Our Group of High Performance Materials in Enviormental & Civil Engineering Department at Michigan State University has an openings for PhD positions to work on Multiscale Modeling of Soft Materials starting sSummer  or Fall 2015.

This paper computationally investigates the effect of martensitic variant strain accommodation on the formation of microstructural and topological patterning in zirconia. We used the phase-field technique to capture the temporal and spatial evolution of embryonic formation of the monoclinic phase in tetragonal single crystals. The three-dimensional simulations were able to capture the formation of all the possible monoclinic variants. We used the multivariant single embryo as an initial condition to mitigate the lack of nucleation criteria at the mesoscale.

Two solids can adhere to each other in the presence of a liquid bridge between them, which is called wet adhesion. When the solid is soft, the liquid bridge can cause deformation in the material, and in turn, the deformation may have dramatic effects on the wet adhesion. To investigate the effect, in this article, we calculate the deformation in two soft layers with different separations and connected by a liquid bridge. We illustrate the effect of deformation in the soft layers on the adhesive force.

Cavitation can be often observed in soft materials. Most previous studies were focused on cavitation in an elastomer, which is under different mechanical loadings. In this paper, we investigate cavitation in a constrained hydrogel induced by drying. With taking account of surface tension and chemo-mechanics of gels, we calculate the free energy of the system as a function of cavity size. The free energy landscape shows double-well structure, analogous to first-order phase transition.  Above the critical humidity, a cavity inside the gel is tiny.

Dislocations are topological line defects in three-dimensional crystals. Same-sign dislocations repel according to Frank’ s rule . This rule is broken for dislocations in van der Waals (vdW) layers, which possess crystallographic Burgers vector as ordinary dislocations but feature “ surface ripples”  due to the ease of bending and weak vdW adhesion of the atomic layers. We term these line defects “ ripplocations”  in accordance to their dual “ surface ripple”  and “ crystallographic dislocation” characters.