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The Sandwich Bending Specimen for Characterizing Adhesive Properties

Published

Author(s)

Donald L. Hunston, Z Z. Miyagi, Carl R. Schultesiz, S Zaghi, H Binson

Abstract

Techniques to characterize the mechanical properties of adhesives in a bond geometry are important because the behavior can differ from that of bulk adhesive samples. Although there are a number of such tests, the simplicity of the sandwich beam specimen makes it attractive. This test involves 3-point bending of a beam made by bonding together two metal strips with the adhesive. For linear elastic materials, the shear modulus of the adhesive can be calculated from the bending stiffness of the beam with either of two published analyses. This paper conducts experiments to examine the sandwich test and the potential to extend it to viscoelastic adhesives since standard viscoelastic test equipment can easily measure 3-point bending. The results show that the stiffness of the sandwich beam is sensitive to the presence of the adhesive throughout most of the interesting range for adhesive properties. Second, when tested as a function temperature and time (or frequency), the stiffness of the beam behaves like a classic viscoelastic property. Finally, in the rubbery, elastic range, the shear moduli calculated from beam tests with thick bonds agreed very well with those obtained from tests on bulk samples for adhesives. In the temperature range where the adhesive is hard (glassy behavior), however, problems were observed for the geometries tested here. Some of these may be attributable to assumptions made in the analyses, and this suggests the need for a new analysis that addresses these limiting assumptions and extends the test to viscoelastic materials.
Citation
Mechanics of Time-Dependent Materials
Volume
7

Keywords

adhesives, bending, epoxy, shear modulus, superposition, viscoelasticity

Citation

Hunston, D. , Miyagi, Z. , Schultesiz, C. , Zaghi, S. and Binson, H. (2003), The Sandwich Bending Specimen for Characterizing Adhesive Properties, Mechanics of Time-Dependent Materials, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851820 (Accessed May 26, 2024)

Issues

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Created December 31, 2002, Updated October 12, 2021