Materials with Controlled Microstructural Architecture

     Optimizing material properties by iterating through a series of experiments - fabricating, characterizing, and repeating - can be time consuming and expensive. Here we propose to develop novel structural materials in a far more rapid and efficient manner using topological optimization methods to predict ideal material architectures and novel textile processing to fabricate those architectures.

     Compared to foams, tubes, or truss architectures, which are common porous structures, we believe 3D weaves offer superior properties such as permeability, specific stiffness, heat transfer, damping, and bioactivity.

Figure 1. Schematics of "standard" weave architecture


                

Figure 2. 3D weaving machine showing bobbins and wires

Heat Transfer Applications

Figure 3. Three flow patterns are explored, with Y as the heating direction. Axial: X direction in and X direction out has the best heat transfer. Birfurcated (fully or focused) both use Y direction in and X direction out, and offer the most uniform surface temperatures.

      Heat transfer properties of Cu weaves were investigated using axial, bifurcated, and distributive flow patterns and heat transfer coefficients, surface temperature distributions, and pressure drops were quantified. Both fluidic and thermal properties are better than those of common porous materials such as foams, fins, and truss architectures.

Damping Properties

      In this research, dynamic mechanical analysis experiments are employed to quantify the damping properties of the woven lattices. The results show that the damping loss coefficients of the woven lattices are comparable to many polymers, but have maximum use temperatures that are far higher than those of polymers.

Figure 4. Loss factor vs maximum service temperature: the high maximum service temperature of NiCr weaves make them s trong candidate materials for damping in extreme environments (Ryan, Stephen M. Szyniszewski et al, Damping behavior of 3D woven metallic lattice materials, Scripta Materialia)

Bio-Scaffolds

      This research is focused on developing the next generation of bio-scaffolds that combine biologically activated coatings with porous scaffolds that possess fluidic permeabilities and mechanical properties that mimic those of native tissues.

      The architectures of the 3D weaves are designed to optimize a combination of fluidic permeability and mechanical stiffness. The 100 to 150 micron diameter 304 Stainless steel or Ti6Al-4V wires are coated with hydroxyapatite after weaving to improve bioactivity and osteointegration.

          

Figure 5. Left: Microscope picture of hydroxyapatite on 304 stainless steel weave. Right: SEM micrograph of hydroxyapatite on 304 stainless steel plate.

     The hydroxyapatite coatings are electrochemically deposited onto the weaves using a phosphate salt aqueous solution containing Ca(NO3)2, NH4H2PO4 and NaNO3. The coating temperature and the applied voltage were varied to maximize the uniformity and adhesion of the coating.