Topics in Designing Low Thermal Expansion Lattices at the Microscale

Topics in Designing Low Thermal Expansion Lattices at the Microscale John Chu Master of Applied Science Graduate Department of Aerospace Science and Engineering University of Toronto 2011 Microscale bi-material lattices with near zero thermal expansion are designed to create a thermally stable optical surface for applications in a space telescope. To facilitate the design, the thermal expansion of a unit cell with spacers is derived analytically and validated via finite element studies. Predicting the lattice behaviour also requires knowledge of the constituent properties. To this end, molecular dynamics simulations are performed to determine the thermal expansion and recrystallization behaviour of aluminum and titanium thin films, and nanoindentation experiments are conducted to extract their elastic-plastic properties. Unit cell configurations giving near zero thermal expansion are obtained through iterative analysis. The resulting designs are analyzed and validated via finite element simulations and shown to exhibit long term stability.