CAMP March Newsletter: Page 3
Professor Pier Marzocca’s work involves functionally graded materials (FGMs). In recent years, FGMs have gained considerable attention in high temperature environment applications such as spacecraft thermal protection systems (TPS), high speed vehicles, and compressor and turbine blades of jet engines. These materials are microscopically inhomogeneous composites, in which the mechanical properties and volume fraction of constituent materials vary smoothly and continuously in predetermined directions throughout the structure. For example in ceramic-metal FGMs, the ceramic plays the role of a thermal barrier that provides the high temperature resistance which protects the metal from corrosion and oxidation, while the metal adds the high strength needed for specific engineering applications. Professor Marzocca and his team are investigating the aero-thermo-elastic modeling and dynamic response of a rotating blade made of functionally graded ceramic-metal based composite materials. The blade is modeled as non-uniform composite thin walled beams which are rigidly clamped at the hub with a specified setting and pre-twisted angles. See Figure 6. The blade rotates with a constant angular velocity and is exposed to a steady temperature field and external mechanical and/or aerodynamic excitations. The effect of the temperature gradient through the blade thickness is considered by taking into account that the material properties are graded across the blade’s thickness according to the volume fraction power law distribution. The equations of rotating thin-walled blades are based on the assumption that the original cross-section of the beam is preserved. This implies that the in-plane strains are assumed to be negligibly small when compared with the axial strain; transverse shear, warping restraint, non-uniformity of shear stiffness, and the three-dimensional strain effects. The Coriolis effect and centrifugal acceleration are also included in the model. Furthermore, the constituent material of the structure features thermo-mechanical isotropic properties. Numerical investigations have highlighted the effects of the volume fraction, temperature gradient, taper ratio, setting angle and pre-twisted angle on the mechanical response of bending (flapping) - bending (lagging) coupled blade characteristics. See Figure 7.
CAMP Professors Receive Funding from Grants for Growth and the Metropolitan Development Authority
CAMP Professors Richard Partch, Don Rasmussen, Devon Shipp, Ratneshwar Jha, and Narayanan Neithalath have received funding from Grants for Growth and the Metropolitan Development Authority. Professors Partch, Rasmussen and Shipp have received funding from Grants for Growth to collaborate with Otis Technology, Inc. and Professor Jha received this type of funding and money from Magna Powertrain in Syracuse.In addition, Professor Neithalath received funding from the Metropolitan Development Authority (MDA) to carry out work with Taylor Concrete Products, Inc. Details about their projects are included in CAMP’s December 2008 newsletter.
Micromechanics of Skin
CAMP Professor Cetin Cetinkaya’s Photo-Acoustics Research and Nanomechanics/Nanomaterials Laboratory team has initiated an exploratory research project to characterize the micromechanical properties of human skin and to understand the penetration mechanics of micro-needles into the corneum stratum (top layer of the skin). The effort includes both an experimental component and a modeling study. In the experimental investigation, the accurate determination of relevant properties of a micro-needle design for optimal penetration performance is one of the chief objectives. The research team has started fabricating micro-needles by using micro-fabrication techniques. See Figure 5. In addition to the penetration mechanisms, the mechanical properties of micro-needles must be understood for failure-free operations.
A set of experiments are underway to determine the most critical mechanical parameters of micro-needles for failure analysis, and to characterize a set of custom-made micro-needles. The data will be helpful in order to design the next generation of micro-needles for various practical applications, such as drug delivery and blood testing. In the modeling effort, the objective is to develop viscoelastic models for skin compliance and micro-needle penetration to achieve skin piercing with a minimal micro-needle failure risk. Data from the experimental effort will be used in the modeling components of this exploratory project to understand how micro-needles penetrate the skin.
FIGURE 5: SEM image of an experimental micro-needle