Multiaxial Nonlinear Viscoelastic Characterization and Modeling of a Structural Adhesive

[+] Author and Article Information
C. F. Popelar, K. M. Liechti

Research Center: Mechanics of Solids, Structures and Materials, Department of Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin, Austin, TX 78712

J. Eng. Mater. Technol 119(3), 205-210 (Jul 01, 1997) (6 pages) doi:10.1115/1.2812245 History: Received December 26, 1996; Revised April 18, 1997; Online November 27, 2007


Many polymeric materials, including structural adhesives, exhibit a nonlinear viscoelastic response. The nonlinear free volume approach is based on the Doolittle concept that the “free volume” controls the mobility of polymer molecules and, thus, the inherent time scale of the material. It then follows that factors such as temperature and moisture, which change the free volume, will influence the time scale. Furthermore, stress-induced dilatation will also affect the free volume and, hence, the time scale. However, during this investigation dilatational effects alone were found to be insufficient in describing the response of near pure shear tests performed on a bisphenol A epoxy with an amido amine hardener. Thus, the free volume approach presented here has been modified to include distortional effects in the inherent time scale of the material. In addition to predicting the global response under a variety of multiaxial stress states, the modified free volume theory also accurately predicts the local displacement fields, including those associated with a localized region, as determined from geometric moiré measurements at various stages of deformation.

Copyright © 1997 by The American Society of Mechanical Engineers
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