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RESEARCH INTERESTS
Nanomechanics of surfaces and interfaces. Theoretical mechanics related to the microstructure of materials. Defect mediated thin-film growth. Theoretical and numerical studies of overlayer/substrate systems that exhibit a form of thin-film growth involving a layer-by-layer mode, subsequently switching to a three-dimensional growth (Stranski-Krastinov). Study of surface defects corresponding to adatoms, vacancies and steps, as well as misfit dislocations; evaluation of their interaction and its influence on relevant kinetic processes. Investigation of adatom effects on the underlying surface using various lattice systems. Interaction between steps and adatoms and the Schwoebel barrier.
- Vibroacoustic absorbing composites.Effects of reinforcing particles on the damping treatments used in automotive structures. Constrained and unconstrained layer systems. Parameters that we will explore along the way will include (but are not limited to) the following: (a)effect of distributed particles on the mechanical properties of a viscoelastic matrix; (b) optimum volume fraction of particles, their distribution and their relation to damping characteristics; (c) preferred geometry of the particles (hollow vs. solid, shape); (d) importance of the particle-matrix interface (perfect bonding vs. frictional sliding); (e) variation of properties with temperature and frequency.
- Mechanisms of failure in composites. Design and reliability analysis. Development of micromechanical models that relate damage to mechanical properties of the individual constituents and their interfaces. Design of composite systems with optimum interfacial properties. Effects of debonding and crack bridging on the overall strength. Weak versus strong interfaces in brittle and intermetallic composites under monotonic and fatigue loading. Transverse failure mechanisms in unidirectional composites. Analytical solutions for the stress field in the vicinity of closely spaced fibers. Micromechanical measurements using a high accuracy strain mapping facility. Characterization of interfacial contact and modeling frictional resistance along interfaces. Voids and microcracks and their influence on the effective material properties.
- Synthesis and characterization of bi-material interfaces. Solid state reactions during processing and their influence on the interfacial bond strength. Effects of the processing and service temperature on the matrix phase distribution and local composition. Synthesis of model composite interfaces of simple geometry using materials of engineering interest with closely controlled and characterized chemistry and microstructure. Planar composite interfaces made in situ by ultra high vacuum diffusion bonding of two substrates. Characterization of interfaces after synthesis and deformation by utilizing transmission electron microscopy methods.
Micromechanics of defects in solids. Inhomogeneities in the context of full and half space geometries. Thermal loading and residual stress analyses using the concept of eigenstrains. Mechanical loading of inclusions near a free surface; effects of the boundary on the local stress field. Imperfect interfaces and their influence on the stress concentration. Random distribution of inclusions and macroscopic mechanical properties. The inclusion method as a tool for modeling fibrous composites. Eshelby's results and the sliding inclusion model.