Oscillatory Shear Rheology for Probing Nonlinear Viscoelasticity of Complex Fluids: Large Amplitude Oscillatory Shear

Linear and non-linear rheological responses of complex fluids are of great interest. Oscillatory techniques are commonly used to analyze the complex fluid rheological behavior. In this chapter, the approach based on large amplitude oscillatory shear (LAOS) is reviewed. Initially, oscillatory shear based on small strain amplitudes is presented along with a brief discussion on relaxation time spectrum. Subsequently, key observable features of LAOS are shown with experimental observations on selected materials. Various applications for which LAOS is being investigated have been described through these examples. Complex fluids such as polymer solutions and melts, emulsions, blends, biological gels, micellar solutions, etc. are being investigated for their non-linear response at large amplitudes during LAOS. In addition to the general response during LAOS, specific material functions being proposed in the literature are discussed. Finally, an example of bulk oscillatory flow is discussed in the context of LAOS behavior of complex fluids.