Enabling design with rheological complexity: intuition and optimization of viscoelastic materials

Abstract

In this thesis, we seek to outline a methodology to enable engineering design based on rheologically complex materials. Traditionally, engineers choose hard materials or simple fluids for design. Complex materials (soft solids and non-Newtonian fluids) greatly increase the design space. Additionally, these materials add functionality (viscoelasticity, nonlinearity) that can achieve diverse performance objectives (user experience, vibration isolation, etc.). Here, we focus on a specific rheological complexity: viscoelasticity. Viscoelasticity introduces a material time dependence, often referred to as memory. The design process with these materials is presented as a multi-step inverse problem that begins with identifying optimal target rheology to meet specified performance objectives. This target rheology remains material agnostic, to be achieved through the design of the viscoelastic material microstructure. A survey of material structures to achieve viscoelastic timescales is reviewed, outlining several design strategies for viscoelastic target properties.