The Design of Tribological Composites for Multifunctional Applications: Model Development and Topology Optimization

As a result of the significant economic and environmental burdens caused by wear, extensive research has been conducted to understand, predict, and control wear to achieve desired performance and lifetimes for tribological systems. Sliding interfaces in many tribological systems must also be multifunctional, prompting the need to optimize for a range of properties and processes. Composites serve as great multifunctional candidates for targeted properties and performance: including mechanical, thermal, electrical, and chemical. However, current material selection and design processes for tribological composites are often trial-and-error, time-consuming and involve significant material and energy waste. This dissertation presents a new design framework that can direct and accelerate the development of tribological composites for combined wear and thermal performance. The framework integrates three main components: (i) wear models that can predict the evolution of key metrics (surface topography, material loss, contact pressure and temperatures) (ii) wear experiments that are used to evaluate and validate the wear models and (iii) topology optimization tools that control the spatial arrangement of materials in tribological composites to achieve target multifunctional performance. In particular, existing wear models are improved and enhanced for the design of rotary and linear wear systems. One of the major contributions is the development of a thermomechanical wear model that includes frictional heat generation and transfer, along with temperature-dependent wear rates. The model developments are incorporated into several topology optimization protocols, and for the first time, a framework to design tribological composites for enhanced frictional heat dissipation is presented. The material distribution within bi-material composites is optimized to minimize temperatures at sliding interfaces while maintaining target wear performance.