  As 2D materials such as graphene, transition metal dichalcogenides, and 2D
polymers become more prevalent, solution processing and colloidal-state
properties are being exploited to create advanced and functional materials.
However, our understanding of the fundamental behavior of 2D sheets and
membranes in fluid flow is still lacking. In this work, we perform numerical
simulations of athermal semiflexible sheets with hydrodynamic interactions in
shear flow. For sheets initially oriented in the flow-gradient plane, we find
buckling instabilities of different mode numbers that vary with bending
stiffness and can be understood with a quasi-static model of elasticity. For
different initial orientations, chaotic tumbling trajectories are observed.
Notably, we find that sheets fold or crumple before tumbling but do not stretch
again upon applying greater shear.

Soft Condensed Matter;Fluid Dynamics