Extensional Flow Of Non-Newtonian Fluid In Fiber Spinning

Non-Newtonian fluid mechanics or rheology is in the intersection of mechanics, modern mathematics, chemistry and engineering. Being a new edge discipline, it has become an important branch of modern fluid mechanics. Non-Newtonian fluid mechanics is the science to study the rheology of non-Newtonian fluid, so rheology of non-Newtonian fluid is equal to non-Newtonian fluid mechanics in modern rheology. While constitutive equation or constitutive theory is the theoretical base of this discipline in the study of materials science and rheology. The introduction of non-Newtonian constitutive relationship is a fundamental breakthrough of classical fluid mechanics, and gives an extra task-fixing the constitutive relationship of fluid. The relationship is expressed by constitutive equation. Constitutive equation can be deduced by using computer calculation to obtain various formulas of material parameters.Liquid crystalline polymer (LCP) is a polymer that exists in liquid crystalline phase in some conditions. It is an anisotropic viscoelastic non-Newtonian fluid. LCP has distinctive properties from the combination of high molecular mass and liquid crystalline phase, which becomes a new high performance polymer in recent years. So the study and development of LCP not only provides a new high performance material and results in the advance of technology and the generation of new technology, but also promotes the development of molecular engineering, synthesis chemistry, polymer physics, polymer processing and polymer applications.The study of LCP is related to non-Newtonian fluid mechanics and rheology, polymer chemistry, materials science and mathematics, which has important scientific value and applied prospect. But the rheologic study of LCP is just about ten years. For constitutive theory is the theoretical foundation of rheology and fluid mechanics of LCP, the first task is to establish and develop the constitutive equation fitting to LCP, that is, the constitutive equation for anisotropic viscoelastic fluid. The constitutive equation of LCP includes microscopic theory and macroscopic theory. At present, most experts use the constitutive equation based on the microscopic theory to study the rheology of LCP.As LCP has good molecular orientation, fibers with high-strength and high-modulus could be produced by the fiber spinning of LCP, for example, Kevlar. But the fiber spinning process of LCP melt not only has the transfer of momentum, energy and mass, but also has the microscopic changes, such as crystal in cooling process and orientation in extensional process. It is a complicated procedure because of the relation of these questions, so the fiber spinning of LCP is a complicated rheologic, physical and chemical process, which has a complex mechanical issue of non-Newtonian fluid mechanics and rheology. The properties of LCP remarkably rely on the microscopic structures in process, for example, molecular orientation provides the LCP with high extensional strength. In order to predict and control the properties of products, that is, enhance the properties of products and reduce the cost of products, it is important that know the flow behavior of anisotropic melt and solution and the microscopic structures in fiber spinning process.In this dissertation, the existing results about the LCP rheology, its theories and methods were summarized. By using co-rotational Oldroyd fluid B model of macroscopic theory, the rheology and the fluid mechanics of the fiber spinning process of non-Newtonian fluid between the spinneret and wind-up spool were studied. Its rheologic properties-viscosity, extensional behavior and spinable property and fluid mechanics-fiber spinning flow, steady flow and orientational flow were modeled by computer, which is the startpoint of the rheologic and fluidmechanical study for the fiber spinning of LCP. Based on the comparison of solving the differential equations, the numerical modeling of fiber spinning flow has been taken by using MATLAB and combining with the fiber spinning characteri...