时间 : 2020年01月09日 10时00分
地点 : 重庆大学A区理科楼010
主办单位 : 工程学部
协办单位 : 航空航天学院
REVERSE ENGINEERING OF THE SHELLS OF MOLLUSKS: AN EXAMPLE OF BIOINSPIRED DESIGN
主讲人 : Roberto Ballarini
Natural composite materials are renowned for their mechanical strength and toughness; despite being highly mineralized, with the organic component constituting not more than a few percent of the composite material, the fracture toughness exceeds that of single crystals of the pure mineral by two to three orders of magnitude. The judicious placement of the organic matrix, relative to the mineral phase, and the hierarchical structural architecture extending over several distinct length scales both play crucial roles in the mechanical response of natural composites to external loads. In addition, natural composites are capable of repairing significant levels of damage that they may experience.
In this talk experimental and theoretical results are first used to show that the resistance of the shell of the conch Strombus Gigas to catastrophic fracture can be understood quantitatively by invoking two energy-dissipating mechanisms: multiple cracking in the outer s at low mechanical loads, and crack bridging in the shell’s tougher middle s at higher loads. Both mechanisms are intimately associated with the so-called crossed lamellar microarchitecture of the shell, which provides for tunnel cracking in its outer s and uncracked structural features that bridge crack surfaces at multiple scales, thereby significantly increasing the work of fracture of the material. Despite a high mineral content of about 99% (by volume) of aragonite, the shell of Strombus Gigas can thus be considered ‘ceramic plywood’ (albeit plywood fails in a different manner than the shell), and can guide the bioinspired design of tough, lightweight structures.
Dr. Roberto Ballarini is Thomas and Laura Hsu Professor and Chair of the Civil and Environmental Department at the University of Houston. He formerly served as James L. Record Professor and Head of the Department of Civil Engineering at University of Minnesota. Ballarini’s multidisciplinary research focuses on the development and application of theoretical, computational and experimental techniques to characterize the response of materials to mechanical, thermal, and environmental loads. He is particularly interested in formulating analytical and computational models for characterizing fatigue and fracture of materials and structures. Ballarini’s research has been applied to problems arising in civil engineering, mechanical and aerospace engineering, materials science, microelectromechanical systems, biological tissues and prosthetic design. He has published more than one hundred papers in refereed journals, including Science and Nature, and several of his research projects have been featured in the popular press, including the New York Times Science Times, American Scientist, Business Week, Financial Times, and Geo. Ballarini is Past-President of the ASCE Engineering Mechanics Institute and currently serves as Editor of ASCE Journal of Engineering Mechanics. He is the recipient of the 2019 ASCE Raymond D. Mindlin Medal.