Traction-separation relations can be used to represent the interactions between two surfaces during separation. In the past, characterizing these interactions, particularly under mixed-mode conditions has been tedious. In this paper, a direct method is proposed to simultaneously determine the normal and shear components of traction-separation relations at any mode-mix, based solely on measurements of the initial crack length, load and load-line displacement and rotation of each adherend in a laminated beam configuration. An analysis of laminated beam configurations that accounts for the normal and shear tractions between two layers is used to establish how the differential equations for the normal and shear separations can be decoupled, even under mixed-mode conditions. Interestingly, the decoupled configurations do not hinder the ability to provide a range of mixed-mode conditions via asymmetries in the mechanical properties and thickness of the layers.
A series of experiments were conducted to extract the vector traction-separation relations between silicon and epoxy over a wide range of mixed-mode conditions for positive and negative shear. A custom-built loading device was developed to provide the measurements alluded to above. Since the vector traction-separation relations are extracted in a direct manner with no a priori assumptions as to their form, it was possible to examine the applicability of potential versus non potential representations of mixed-mode traction-separation relations for this interface.
About the Speaker
Kenneth M. Liechti is the Zarrow Centennial Professor of Engineering at the University of Texas at Austin, where he is a member of the faculty of the Department of Aerospace Engineering & Engineering Mechanics. He is the University Education Director for the NSF Nanosystems Engineering Research Center (NERC) for Nanomanufacturing Systems for Mobile Computing and Mobile Energy Technologies (NASCENT). He received his PhD in Aeronautics from the California Institute of Technology. Professor Liechti has made contributions to interfacial fracture mechanics, nonlinear viscoelasticity and the mechanics of contact, adhesion and friction at increasingly smaller scales. Dr. Liechti is a coauthor with Dr. Bedford on the textbook "Mechanics of Materials". He is a Fellow of SEM, ASME, AAM, the Adhesion Society and an Associate Fellow of AIAA. He was the 2015 recipient of the Adhesion Society’s Award for Excellence in Adhesion Science, sponsored by 3M. He recently received the Murray Medal from the Society of Experimental Mechanics. Dr. Liechti was Chair of the Executive Committee of the Applied Mechanics Division of the American Society of Mechanical Engineers and served on the Executive Board of the Adhesion Society.
Host: Professor Yuhang Hu