FIBER STABILITY ANALYSIS FOR IN-SITU LIQUID-CRYSTALLINE POLYMER COMPOSITES

We present a simple mathematical model based on classical theories of macroscopic elasticity that provides a fundamental description of the liquid crystal polymer (LCP) fiber break-up instability that is observ ed during the annealing of in-situ liquid crystal-thermoplastic polyme r composites. The thermodynamic model is solved using a number of cons istent simplifying assumptions, and is restricted to thin liquid cryst al polymer fibers. A significant feature of the liquid crystal surface energy incorporated in the model is the elastic storage due to deviat ions of the macroscopic orientation and of the orientational order fro m the preferred equilibrium values. The model predicts that thin LCP f ibers are unstable to periodic surface perturbations that eventually w ould produce fiber break-up and lead to an array of LCP droplets, as i n the case of Rayleigh's fiber instability. The additional liquid crys talline elastic storage modes incorporated in the model, but not prese nt in isotropic melts, tend to increase the magnitude of the critical wave-length for fiber break-up over that given by the Rayleigh criteri a (i.e., fiber circumference) by a relatively small factor that depend s on the ratio of the interfacial tension and the nematic anchoring en ergy.