Woodruff School of Mechanical Engineering
COE/Structural Mechanics Seminar
An overview of durability challenges for fiber-reinforced polymer composite structures
Prof. Valeria La Saponara
Department of Mechanical and Aerospace Engineering Advanced Composites Research, Engineering and Science (ACRES) Research Group University of California, Davis
Tuesday, September 3, 2013 at 3:00:00 PM
MRDC Building, Room 4211
Fiber-reinforced polymer composite structures have been introduced since the 1970s in applications where weight is a major design parameter. They have been gaining much recent attention because of their extensive use in new aircraft (Boeing 787, Airbus A350, F-35), wind turbine blades, new pedestrian and vehicular bridges, retrofitting of structurally deficient bridges, new ships, trains, cars, etc. Composites exhibit complex damage modes such as delamination, fiber cracks, matrix cracks, fiber/matrix interface debonding, etc. In service, these modes may be triggered by many factors, e.g. thermo-mechanical fatigue, impact, environmental and chemical damage, manufacturing defects, overloads, and a combination of all of the above. This presentation is an overview of three diverse research topics related to the durability of composite structures, and their challenges. 1) Improvements of crashworthiness and energy absorption with a material-based mechanism, a bistable structure. Such a structure is composed of materials that have appropriate trade-offs between strength and elongation to failure, resulting in a fail-safe mechanism under static tension. Bistable structures may be tuned to achieve desired energy absorption per weight. Also, a successful design inspired to bistable structures has been devised for impact loading. 2) Investigation on smart composite structures, where structural health monitoring is carried out either with off-the-shelf embedded piezoelectric transducers, or with sprayed carbon nanotube-based conductive films. An overview of the methods used (Gabor wavelet transform, Electrical Impedance Tomography), benefits and drawbacks will be discussed. 3) Study of thermo-chemical degradation of structural epoxy-based adhesive and polymeric composites due to contaminants typical of aerospace operations. We have shown that common operational fluids (hydraulic fluid, unmixed jet fuel additive, common aircraft cleaning compounds) represent a significant risk to these materials. Results from experiments and two conventional (Fickian and Langmuir) diffusion models are shown.
Dr. Valeria La Saponara received her B.Sc. degree summa cum laude in aerospace engineering from the University of Naples, Italy. She worked for two years as a research fellow at the MARS Center, Italy, a subcontractor of NASA and the European Space Agency. She received her Ph.D. in 2001 in Aerospace Engineering from the Georgia Institute of Technology. After working as instructor in Civil and Environmental Engineering at Georgia Tech for one year, she became an assistant professor in Mechanical Engineering at the University of Utah. In July 2005, she joined the faculty of Mechanical and Aerospace Engineering at the University of California, Davis, where she was promoted to the rank of associate professor with tenure, effective July 2011. In 2007 she received a CAREER Award from the National Science Foundation. Dr. La Saponara’s research focus is to improve the durability of composite structures for aerospace, mechanical, civil and wind engineering applications.
Refreshments will be served.