This project will conduct experiments on “low-wear polymer composite” materials. These materials consist of particles in a polymer matrix. They are often used to reduce friction and mechanical damage (called “wear”) between sliding surfaces. During sliding, low-wear composites form protective films on the sliding surfaces. The project will investigate how polymers, particles, and opposing surface interact to create these protective films. Results will advance predictive design of polymer composites which decrease friction and wear. Friction wastes energy, while wear causes mechanical failures. Therefore, improvements in low-wear materials will benefit a wide range of manufacturing applications. These include bearings in cars, gears in machinery, or hip implants. Further benefits will come from educational activities developed during this project. These include training undergraduate students in advanced materials testing and teaching middle and high school students about the science and engineering of materials, friction, and wear. This research will develop cause-effect relationships between composite structures and their properties. It will focus on how the wear behavior depends not just on the mechanical properties of the filler particles, matrix, and counterface material, but also chemical properties. The novelty of proposed research is that interactions between particles, matrix, and the counterface will be investigated across a wide range of length scales. This work will be conducted on model thermoplastic polymers and a select range of filler/counterface chemistries that promote low and high wear. These measurements will be enabled through custom macroscale tribometry, nanoscale mechanics using scanning probe microscopy, as well as multi-length scale spectroscopic characterization. The scientific outcome of the proposed research will be predictive design rules for mitigating wear in polymer composites. This project represents a transformative step toward p