Manufacture and Characterization of Nanocomposites: (1) Synthesis, characterization and modeling of porous nanostructured materials, including organic, polymer crosslinked silica aerogels. This is a class of strong lightweight materials with superior thermal insulation, acoustic attenuation, energy absorption and structural load carrying capabilities. It has potential for use as multifunctional materials in lightweight vehicles; and (2) Manufacture and characterization of carbon nanotube sheet reinforced polymer matrix composites.
Viscoelasticity: (1) Long-term durability of polymers and composites under quasi-static and fatigue loading conditions; (2) Dynamic behavior of materials at high strain rates using split Hopkinson bars and ultra-high speed photography and ultra-high speed photography (62 color frames, up to 4 million frames per second); (3) Mechanical behavior of plastic foams, and fiber reinforced plastic foams under quasi-static loading, and dynamic loading conditions using digital image correlation, micro-computed tomography; and (4) Nonlinear constitutive modeling of polymers under multiaxial loading conditions.
Experimental Techniques: (1) Measurements of large nonlinear surface deformations using digital image correlation with the implementation of second order displacement gradient terms (strain gradients), as well as third-order displacement gradients ( in addition to the first order displacement gradient terms); (2) Development of highly sensitive miniature split Hopkinson tension/compression bars for sensing small force for measurements of complex modulus in the auditory frequency range for soft tissues such as human tympanic membranes; (4) Nanoindentation for measurements of both bulk and shear relaxation functions using both Berkovich and spherical indenters.
Nanomechanics: (1) Methods for measurements of linear viscoelastic functions in both time- and frequency-domains using nanoindentation; and (2) Determination of the mechanical behavior of single crystals at microscale using nanoindentation and simulations using crystal plasticity.
Computational Simulations: (1) 2D and 3D structured mesh refinement, and parallel processing techniques for Material Point Method (MPM); (2) Simulation of dynamic problems with complex contact surfaces, such as compaction of bulk metallic glass foam involving large nonlinear deformations and complex contact surfaces using MPM under parallel processing; (2) Simulation of dynamic crack growth using MPM and normal/tangential cohesive laws; (3) Seamless coupling between molecular dynamics (MD), discrete dislocations and continuum.
Ear Biomechanics: (1) Measurement of the viscoelastic properties of tissues in human ears such as tympanic membrane (eardrum) using nanoindentation; (2) Measurement of viscoelastic properties in the frequency domain; (3) Measurement of nonlinear mechanical properties of ear tissues under overpressure using full-field non-contact optical techniques.
Mechanics of Granular Materials: (1) Characterization of mechanical behavior (stress-strain relationship, fracture toughness) of individual grains by nanoindentation; (2) Deformation and fracture behavior at mesoscale, including characterization of force chains using incremental digital volume correlation analysis of in-situ µ-CT volumetric images; (3) Dynamic behavior of soil (sand, clay, and synthetic “natural soil”) using 85-ft long split Hopkinson pressure bar and ultra-high speed photography.
Manufacturing Processes: (1) Development of an innovative sheet metal slitting/cutting technique using shear slitting/cutting when two rotary blades forming a rake angle are not in contact. The new method produces clean edge without burr/debris formation, while extending the service life significantly; (2) Modeling stress/strain distribution in 3D winding of viscoelastic films to determine the film flatness upon unwinding.