Soft elasticity and microstructure in smectic C elastomers

Smectic C elastomers are layered materials exhibiting a solid-like elastic response normal to the layers and a rubbery response in the plane. The set of strains K C minimizing the elastic energy contains a one-parameter family of simple stretches associated with an internal degree of freedom coming from the in-plane component of the director. We investigate soft elasticity and the corresponding microstructure by determining the quasiconvex hull of the set K C and use this to propose experimental tests that should make the predicted soft response observable.