Light weighting vehicles, infrastructure, and products not only maintain or even enhance performance, but promise to positively impact energy sustainability with numerous potential applications in both defense and civilian sectors. Consequently, the design and production of lightweight metals and reinforced composites with superior combinations of properties in the finished product are of utmost importance, particularly in the transportation and energy sectors. Georgia Tech faculty employ an integrated approach that brings together expertise in materials science, manufacturing, product design, systems engineering, and data/information sciences to address this challenge. Capabilities include:
- The Mechanical Properties Research Laboratory at Georgia Tech is a leading US university laboratory in experimental studies of deformation, fracture and fatigue of structural materials, as well as coupling such experiments with mulitiscale modeling and simulation.
- A broad suite of experimental facilities and customized protocols that allow high throughput acquisition of multiscale multi-modal measurements (e.g., microscopy, orientation image mapping, indentation, strain mapping, residual stress measurements, non-destructive imaging techniques).
- A broad suite of experimental facilities for manufacture of polymer composites including a unique custom-made SMC production line which allows for high throughput manufacture of SMC composites at small scale but of industrial specifications that can produce composites that cover a large design space in terms of material composition and micro-structure and processing conditions.
- A broad suite of multi-physics multiscale modeling approaches that span a wide range of length and time scales (e.g., atomistics, dislocation dynamics, phase-field, Monte-Carlo, crystal plasticity, finite element).
- Novel analytic tools for extracting property-structure-property linkages from large experimental and simulation datasets and presenting them in forms that are easily accessible by design tools.
The image at right illustrates microstructure evolution in static recrystallization of AZ31 (a Mg alloy) using electron back-scattered diffraction (EBSD). Colors in this image are associated with specific crystal lattice orientations. Observe the preferred nucleation of recrystallization in compression and double twins (produced in the prior deformation) and their subsequent slow growth.
An example is shown below of how spherical nanoindentation combined with EBSD may be used to quantify the role of grain boundaries in the plastic deformation of polycrystalline metals. In the top image, the deformed coarse-grained sample is shown with the specific grain boundary regions studied. For each grain boundary studied, the local percentage increase in critical resolved shear stress is measured as a function of the distance from the grain boundary (on both sides). Each point in these plots represents a measurement from one indentation. Consequently, the plot on the left shows indentation measurements from a very large array of indentation measurements. The plot, bottom, summarizes the measurements in the top image in a specific low-dimensional representation that aims to quantify the size and amount of strain hardening in the transition region as a function of the difference in Taylor Factors (computed for grain orientation on either side of the boundary based on the macroscopic deformation imposed on the bulk sample). A limited number of observations indeed show an insightful trend.
As fuel costs and environmental concerns continue to mount, so does the demand for composite materials for aerospace and transportation applications. Polymer composites are inherited lighter than their metallic counterparts resulting in significant weight reduction of the aircraft/vehicle which means improved fuel efficiency, less air pollution and smaller carbon footprint. In addition, composites allow for easy manufacture and assembly of geometrically complex components, do not fail catastrophically and offer improved resistance to corrosive environments. Research at Georgia Tech focuses on overcoming these challenges. Out-of-autoclave processes are used such as vacuum assisted resin transfer molding (VARTM) and SMC (sheet molding compound) method, using a lab scale pilot SMC line, in combination with compression molding. Fiber wetting by the resin and interfacial strength are improved by introducing nanomaterials such as carbon nanotubes or graphite nanoplatelets at the fiber-polymer interface using special compounding methods.