Texture evolution of sheared liquid crystalline polymers: Numerical predictions of roll-cells instability, director turbulence, and striped texture with a molecular model

Abstract

In the present work, we study the textural evolution of liquid crystal polymer (LCP) systems under planar shear at high shear rates, based on computational simulations using a recently developed molecular model with distortional elasticity [Feng etal. (2000)]. We concentrate our attention on the final striped texture that is observed in real LCP systems and on the secondary flow instability characterized by the formation of cross-sectional roll cells that is believed to represent the starting point of the orientational evolution. We verify that the theoretical model is capable of predicting a texture evolution that captures many of the essential features of the interplay between shear flow and LCP microstructure that are observed in experiments. We identify the mechanisms at play and the relative roles of the various forces in determining the evolution of texture at moderate shear rates and how they depend on the Deborah number, which is the characteristic parameter that defines the different regimes at moderate and high values of shear rate.