Alan Taylor Zehnder
Alan Zehnder received his doctorate in mechanical engineering with a minor in materials science from the California Institute of Technology. He stayed on as a postdoctoral research fellow for one year, and joined the Cornell faculty in 1988.
In 1993 he was the faculty member in residence in Hamburg, Germany, for the Cornell Engineering Abroad program. He was a visiting Professor at Caltech in the 1996-97 academic year. In summer of 1998 he served as a Senior Faculty Fellow at the Naval Surface Warfare Center in Carderock, Maryland. In 2004 he was a Guest Professor at the Vienna University of Technology.
Zehnder is a member of the American Society of Mechanical Engineers, and the Society for Experimental Mechanics.
My current research focuses on the fracture of nanoscale systems, nonlinear dynamics of nanomechanical oscillators and damage tolerance of polymer matrix composite materials.
Nanoscale systems, although still large enough to obey the laws of continuum mechanics, show surprising effects due to their small size. For example, the nanomechanical oscillators can interact with light through heating and optical interference to become self oscillating. This nonlinear dynamical system exhibits a rich range of behavior including multiple limit cycles, entrainment of limit cycles to small amplitude forcing, and other phenomena.
Nanoscale structures can have strengths close to the theoretical strength of the material. Although this strength degrades after extended exposure to air, we found that by coating surfaces with a self-assembled monolayer high strengths are maintained. Research is underway to fully explore the effects of surfaces on the strength of nano-scale systems.
Composite laminate sandwich panels are well known for their high specific strength and stiffness. However a concern is low energy impacts that may compromise strength. An integrated experimental and numerical study is underway to provide design guidelines and predictive models for assessing the damage resistance and tolerance of sandwich structures. Working with colleagues in MAE and CEE I am beginning to work on structures and materials research with applications to utility scale wind energy systems.
Past research topics include dynamic fracture, development of a million frame per second infrared imaging system, fracture in plates and shells, high speed metal cutting, metal-ceramic interface fracture, fault propagation folding modeling and the use web-based tools in undergraduate engineering education and failure and damage tolerance of high temperature properties of polyimide matrix composites (PiMC's).
I have a broad range of teaching interests in undergraduate mechanics, and engineering mathematics. At the graduate level I teach solid mechanics, fracture mechanics and experimental mechanics.
- 2012. "Damage Characterization of Quasi-Statically Indented Composite Sandwich Structures." Journal of Composite Materials . .
- 2012. "Anchor deformations drive limit cycle oscillations in interferometrically transduced MEMS beams." Finite Elements in Analysis and Design 49 (1): 52-57. .
- 2010. "Delamination of Moisture Saturated Graphite Polyimide Composites Due to Rapid Heating." Composites - Part B 17: 568-577. .
- 2009. "Blistering of Moisture Saturated Graphite/Polyimide Composites Due to Rapid Heating." Journal of Composite Materials 43 (2): 153-174. .
- 2006. "Methyl Monolayers Improve the Fracture Strength and Durability of Silicon Nanobeams." Applied Physics Letters 89 (23). .
Selected Awards and Honors
- Rudolf Kingslake Medal and Prize (Society of Photographic Instrumentation Engineers) 1988
- Charles Lee Powell Fellow 1985
- TRW Advanced Technologies Fellow 1984
- BS (Mechanical Engineering), University of California- Berkeley, 1982
- MS (Mechanical Engineering), California Institute of Technology, 1983
- Ph D (Mechanical Engineering), California Institute of Technology, 1987