Nonlinear Oscillatory Shear Mechanical Responses

Abstract

Mechanical dynamic oscillatory shear test is generally used to characterize and investigate mechanical properties of complex fluids or soft matters. Especially, small amplitude oscillatory shear (SAOS) tests are the canonical method for probing the linear viscoelastic properties of complex fluids because of the firm theoretical background and the ease of implementing suitable test protocols. Material functions of SAOS tests are analogous with dielectric functions from dielectric spectroscopy. However, recently nonlinear responses under large amplitude oscillatory shear (LAOS) flows are also under the spotlight due to usefulness to characterize complex fluids. In this chapter, LAOS tests are reviewed. The key to successful LAOS test is the analysis and fundamental understanding of the nonlinear mechanical responses. To analyze nonlinear responses, there are several analyzing methods and various nonlinear material functions suggested by several researchers. Among the several methods available, FT (Fourier transform)-rheology is intensively reviewed. Finally, several applications to investigate complex fluids (polymer melt and solution, polymer composite and blend, emulsion and block copolymer, and so on) are introduced.