A Design Methodology for Thick Advanced Composite Structures
Tarih:
Konum: 241
Dr. K. Levend Parnas Department of Mechanical Engineering Middle East Technical University Time : 18 February 2015, Wednesday at 10:00 Place : Room 241 Abstract Structures made of thick composites have been attracting a wide interest with an increase in demand for lighter and stronger parts in especially aerospace, wind and automotive industries. While the replacement of thin metal parts with composite counterparts is becoming an aged story, relatively thick parts however emerge as a new challenge. Their design requires the development of new methods and approaches. The presentation will address some of these issues and summarize the results of a recent study completed recently. Demands for higher energy efficiency and performance enhancement driven by today’s markets of extreme competition dictates a shift in paradigms in the design of advanced composite structures. With these influences, even critical structural parts are forced to be replaced by thick composite ones which require a different approach both in terms of design and manufacturing. A study was initiated to establish a design methodology for such parts. The aim is to reduce experiments and accelerate the design process as much as possible in order to attain lighter and more reliable advanced composite parts. The method developed in this study is planned to be used in thick parts including rotor blades of helicopters and wind energy systems, and aerospace industry. The study is basically composed of 3 phases. In the first phase, a material characterization study is conducted in the form of an extensive test program. It consists of standard and non-standard tests on specimens to determine mechanical and thermo mechanical properties including failure behavior of the materials. In addition to in-plane properties, 3D out-of plane properties are also obtained. In the next phase of the study, an extensive finite element analysis program is conducted for the root section of a helicopter blade to create a specific approach for thick composites. These studies are conducted in 3D by considering the geometric non-linearity due to large displacements. Various progressive damage models based on a number of 3D failure theories are also utilized in this program. The progressive failure behavior of models are obtained and results are compared with experimental studies. In the structural test program as the final phase, models developed in the analytical program are verified by providing similar loading and constraint conditions. Displacement, load, and strain data at various locations on specimens are recorded. Specimens are loaded up to the load carrying limit of structures. Some structures are tested under fatigue load representing the service conditions. By using the experimental findings, the results obtained in the analytical program are verified and then the design package is given the final configuration in the form of a set of design guidelines. Biography Dr. Levend Parnas received his B.S. degree in Mechanical Engineering from the Middle East Technical University in 1982. He received his M.S. degree from the same department in 1985. He then moved to Georgia Institute of Technology for a Ph.D. study in Aerospace Engineering with a scholarship and obtained the degree on Failure Mechanisms in Advanced Composite Structures in 1990. He stayed in Georgia Tech for a Post Doctoral position for a year before joining to the Department of Mechanical Engineering, Middle East Technical University as Assistant Professor in 1992. He has been Professor in the same department since 2003. During his tenure, he was involved in many research projects and served as a consultant to a number of institutions in the defense industry in various R&D projects. His research interests include computational and experimental investigation of mechanics of advanced composite structures, biomechanics, impact mechanics, and manufacturing of composite structures.