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Failure Mechanisms of Sandwich and Cellular Materials

August 30, 2013 | 11:00 AM – 12:00 NOON
Nedderman Hall 108 | Seminar Flyer

Seminar Speaker

E.E. Gdoutos

Full Member, Academy of Athens; Adjunct Professor, Northwestern University; Distinguished Clark Millikan Visiting Professor, California Institute of Technology

Abstract

Sandwich structures consisting of strong and stiff facings and light weight cores offer improved stiffness and strength to weight ratios compared to monolithic materials. Under flexural loading the facings carry almost all of the bending, while the core takes the shear loading and helps to stabilize the facings. Facing materials include metals and fiber reinforced composites. The latter are being used in advanced applications due to the large strength-to-weight ratio. The core materials mainly include honeycombs, cellular foams and wood. In the present seminar the failure behavior of composite sandwich beams subjected to three- and four-point bending will be presented. The beams were made of unidirectional carbon/epoxy facings and various core materials including PVC closed-cell foams, a polyurethane foam and an aluminum honeycomb. Various failure modes including facing wrinkling, indentation failure and core failure were observed and compared with analytical predictions. It was established that the initiation, propagation and interaction of failure modes depend on the type of loading, constituent material properties and geometrical dimensions. The crack growth behavior of polymeric foams under mixed-mode loading conditions will also be presented. Polymeric foams are anisotropic materials and crack kinking occurs even though the applied load is perpendicular to the crack plane. The stress analysis of the plate was performed by finite elements. Crack trajectories for various angles of the orientation of the axes of orthotropy of the material with respect to the applied load were obtained.

Bio

Dr. Emmanuel E. Gdoutos is Full Member of the Academy of Athens, the most prestigious academic institute in Greece. He served as Professor of Theoretical and Applied Mechanics of the Democritus University of Thrace, Greece and is Adjunct Professor at Northwestern University, and Distinguished Clark Millikan Visiting Professor at California Institute of Technology.

He is member of the European Academy of Sciences and Arts, of Academia Europaea, of the European Academy of Sciences, Foreign Member of the Russian Academy of Engineering, the International Academy of Engineering, and the Russian and Bulgarian Academies of Sciences. He is Fellow and honorary member of many international societies. He was awarded a Doctorate Honoris Causa from the Russian Academy of Sciences and from the University of Nis, Serbia and received many international awards He is Honorary Citizen of the Prefecture of Lesvos, Greece.

He served as President of the European Structural Integrity Society, the European Society for Experimental Mechanics and the Society for Experimental Mechanics. He taught in many universities in Greece and USA. His research interests include: experimental mechanics, fracture mechanics, advanced composite materials, sandwich construction and nanotechnology. He authored/co-authored more than 300 papers in refereed journals and conference proceedings and 40 books.