Structural Mechanics and Materials Behavior
Introduction
August 1, 2003
Aerospace vehicle applications have always been at the cutting edge of structures and materials research because of the increased demand for lightweight construction as well as the need to combine safety with performance. New, advanced materials are constantly proposed, such as composites with toughened thermosetting matrices, thermoplastic composites, and metal-matrix or ceramic-matrix composites. The challenge of new materials notwithstanding, many active research issues remain regarding the conventional metallic aero-structures, such as life extension in aging aircraft and proper methods of vibration control.
Georgia Tech offers graduate studies and research in structural mechanics and material behavior (SMM) of aero-structures. Specific areas include computational mechanics, composite structures, fracture and fatigue, damage tolerance and failure prediction, experimental mechanics, thermal and environmental effects and non-destructive evaluation, structural stability (buckling/postbuckling), adaptive structures, structural health monitoring, and system identification. The sructures faculty actively participate in this ever-evolving field through their sponsored research. They direct research grants from ONR, ARO, AFOSR, the National Rotorcraft Technology Center (NRTC), and numerous industrial sponsors.
Graduate research and education challenges in aero-structures and materials are demonstrated by the many structural parts of commercial and military airplanes and space vehicles now being made of new, advanced materials. Examples of primary carbon-epoxy structures include vertical tails of the Airbus A300-340 series, the Boeing 777 transports and the wings and fuselages of the B-2 military aircraft, almost the entire Comanche helicopter, and satellites and various components of the space shuttle (especially the new X-33 version). Structural design criteria for these aero-structures include damage tolerance requirements specifying the ability of a structure to operate safely with initial defects or in-plane damage. Defects such as porosity, delamination, lack of bond between co-cured parts, and wrinkles in fibers can develop when composite materials are processed. Low-velocity impacts can cause damage that may not be readily visible. High-velocity impacts from parts of rotating machinery that fail and penetrate the skin and supporting structure, or from ballistic damage, can have even more serious airworthiness implications. New concepts in design, such as sandwich or hybrid material construction, new manufacturing techniques (which may introduce undesirable residual stresses and deformations) and new material developments requiring new methods of analysis and testing make advanced education in structures and materials even more necessary and rewarding.
Research in active and passive control of structural systems is also being applied to the design of earthquake and wind resistant structres under the Mid-America Earthquake Center, one of three U.S. centers funded by the National Science Foundation in this research area.
Some of the areas of intense activity in which graduate students participate as research assistants include: damage tolerance/fatigue/fracture; airworthiness; impact-resistance; efficient and accurate computation tools (finite elements, etc.); modeling of the mechanics of manufacturing; new structural design concepts (ply drop-off, sandwich construction, elastic tailoring); advanced topics in structural mechanics such as anisotropic elasticity and plate/shell higher order or asymptotic theories; and diagnostic methods including C-scan, acoustic emission, and X-ray.
The Structures Laboratory is well-equipped with advanced test frames and optical equipment for the remote monitoring of cracks, as well as a variety of non-destructive testing equipment and related computerized data acquisition systems. An exclusive facility is available for manufacturing of composite specimens; this facility includes a filament winder and an autoclave,. Dedicated computer workstations can be used for large-scale computational research and stress analysis. Furthermore, interdisciplinary research and education opportunities exist through the Center for Composites Education and Research (CERC), offering a graduate certificate in composites and the Center of Excellence for Rotorcraft Technology (CERT), offering opportunities for involvement in advanced rotorcraft structures.
