Research Overview

Efforts to increase fuel efficiency and reduce CO2 emissions are driving increases in the temperature at which gas turbine engines operate. Our group is exploring the mechanisms by which current coatings function and eventually fail as the operating temperature rises. It is developing and exploiting state of the art deposition techniques such as electron beam directed vapor and coaxial plasma deposition and plasma spray processes to create coatings that provide much better protection.

Nature makes pervasive use of cellular materials for our bones, tree trunks, insect exoskeltons, etc. Our group is developing synthetic, topologically optimized cellular materials from high performance materials such as carbon, silicon carbide and aluminum oxide fibers using state of the art polymers and light metallic alloys to interconnect them. These materials/structures have very high specific compressive strengths and offer many opportunities to make lighter structures for automobilies, planes, ships and space vehicles.

 

The sudden localized application of a stress to a structure by explosively created shock fronts sets into motion a comlex sequence of processes active across multiple length and time scales. We and our collaborators are investigating these phenomena and using our emerging fundamental insights to motivate the development of materials that provide much better protection. Examples include impact energy absorbing materials with cellular structures that compress when inpulsively loaded. These materials reduce impuse transfer for shocks propagated in water (and to lesser exten air). When configured as the cores of sandwich structures, dynamic deflections can be reduced greatly for all types of shock loading.

 

 

The impact of a projectile with a material suddenly creates very large stresses in both the material and the projectile. These stresses then activate mechanisms of deformation (such as dislocation motion and twinning) and fracture in metals and ceramics, and various molecular sliding and chain scission processes in polymers. These are rate dependent and therefore the material and projectile responses are a function of the impact velocity. Our group brings this mechanistic perspective to the design of novel material systems and multi component cellular topologies that impede pentration in light weight configurations.

 

Cellular materials are widely used for thermal management. Those made from good thermal insulators (such as polymers) with a closed cell morphology have extremely low thermal diffusivity. Those made from high conductivity metals with a lattice (open cell) topology have attracted significant interest for heat exchangers. These structures can simultaneously support large bending stress while also enabling large thermal fluxes to be dissipated to a cooling flow. They are an example of a multifunctional structure. Our group also investigates multifunctional applications of cellular structures configured as heat plates for the leading edges of hypersonic vehicles and for controlling jet engine exhaust plumes.

 

The emergence of increasingly mathmetical descriptions of the interatomic forces between atoms in materials, combined with rapid increases in computation capabilities now allow realistic atomistic sacle simulations of their structure and its evolution. Our group has applied this approach to understand the atomic assembly of thin films and coatings by vapor phase processes. These fundamental insights have been used to design new thin film deposition processes which use low energy ion beams to accelerate low temperature atomic assembly.