Electrorheological Material-Based Smart Structures

Vibration of structures and structural components, such as helicopter blades, fuselage skins for airplanes and panels of submerged vehicles, can cause fatigue and eventual failure of the structure, acoustic radiation (sound) from it, and in some cases, alter the mean performance characteristics. Due to these types of vibration problems, the noise in the passenger compartment of a helicopter can become intolerable and, furthermore, for a wide range of commercial and military vehicles, noise reduction due to structural vibration is a major concern. Rather than accepting the vibration of the structure, it is now possible to sense either the vibration or radiated acoustic wave and change the structural response in real-time. This is done, for example, by changing the actual properties of the materials comprising the structure, such as an electrorheological (ER) material. The concept of an ER material is indicated in the schematic below. A suspension of dielectric particles in a liquid takes the form of a random, non-polarized matrix. When a voltage is applied across the plates, the dielectric particles form a chain, thereby changing the material of properties. Taken as a whole, this configuration of the particle suspension in the liquid between two plates is a form of an adaptive structure.

This concept of smart structures and their control is interdisciplinary, and includes principles of solid mechanics and control theory using neural networks. I became involved in this area when I was working for Lord Corporation. We obtained a patent on using electrorheological suspensions for the control of structures. After joining the faculty at Lehigh, funding from the National Science Foundation and the Army Research Office allowed us to establish research programs in this area. Melek Yalcintas has focused on development of a better theoretical understanding, backed by experiments, of how these electrorheological materials can change the characteristics of structural response.

We are, of course, interested in active involvement with industrial concerns. Lord Corporation, Lubrizal Corporation, Allied Signal, and other industrial groups have visited us recently. Our interactions have also extended to the United Kingdom, where there is considerable interest in ER materials, especially at Sheffield University, and to The Heat and Mass Transfer Research Institute in Minsk, Belarus. We are currently exploring possibilities for more formal collaborative programs with these groups.

I try to meet with Melek and other students in my group on an individual basis at least once a week. In addition, we hold group meetings every week to discuss collaborative and interdisciplinary issues. We find that this frequency of interaction allows us to progress aggressively or consistently towards our research goals.

I became interested in the general area of solid mechanics and vibrations during my graduate research at Middle East Technical University and the University of Arizona. When I arrived at Lehigh, I found Professor Coulter’s project to be particularly interesting, because it incorporated a diversity of engineering disciplines, including solid mechanics, dynamics, and fluid mechanics, not to mention the area of control systems involving neural networks. Once I became involved in the research program, I found that there were a number of possibilities for publishing jointly with not only Professor Coulter, but also Professors Voloshin in our Department and Burke in Industrial Engineering in the areas of fiberoptic detection and neural network modeling respectively. These articles have appeared in journals such as the Journal of Intelligent Materials and Structures and the American Society of Mechanical Engineers' Journal of Vibrations and Acoustics and related publications. Moreover, Professor Coulter and I have alternated in presenting our work at national meetings. I have enjoyed hosting visits from representatives of Lubrizal Corporation, Allied Signal, and other firms who have taken an interest in our work here at Lehigh. The opportunity to formulate presentations, conduct tours of our laboratories, and related activities in communicating our results to those outside Lehigh have been an important part of my graduate study.

My communication with graduate students in our group, as well as other groups in the department, is also important. The frequent meetings with Professor Coulter serves as a stimulus for new research directions and joint involvement of members of our research group.

Melek Yalcintas, Ph.D. Candidate