College of Engineering
Materials Engineering Department
BS in Materials Engineering
Dr. Trevor Harding, Dr. Thomas Mackin
Polymer foams are the material of choice for applications that require comfort, cushioning, and high energy absorption. While popular, the relationship between their microstructure and their mechanical properties is not yet strongly predictable. The aim of this project is to look at the different relationships between the area or volume occupied by pores compared to the amount of solid material and determine which method of quantifying this relationship will provide the best prediction of mechanical properties. To examine this relationship, foams of various densities made from either ethylene-co-vinyl acetate or thermoplastic polyurethane were first physically characterized through three methods: (1) density measurements, (2) calculating the area occupied by pores compared to the overall area of the cross-section, using scanning electron microscope (SEM) images, and (3) using SEM images to develop a representative cell for each polymer at each density. Next, compression tests were performed to characterize the elastic, plastic, viscoelastic, and anelastic properties of the foams. Statistical models were used to relate physical characteristics to mechanical properties, and they showed that density provides accurate predictions of the Young’s modulus for EVA and TPU, yield strength for EVA and TPU, and area of hysteresis for EVA. Future work can focus on determining whether the final results can be extended to account for viscoelastic behavior and higher strain rates.