Mechanics of Time-Dependent Materials

, Volume 7, Issue 1, pp 71–88 | Cite as

The Sandwich Bending Specimen for Characterizing Adhesive Properties

  • Donald Hunston
  • Zenichi Miyagi
  • Carl Schultheisz
  • Shahrooz Zaghi
Article

Abstract

Techniques to characterize the mechanical properties ofadhesives in a bonded geometry are important because thebehavior can differ from that of bulk adhesive samples.Although there are a number of such tests, the simplicity ofthe sandwich beam specimen makes itattractive. This test involves three-point bending of a beam madeby bonding together two metal strips with the adhesive. Forlinear elastic materials, the shear modulus of the adhesive canbe calculated from the bending stiffness of the beam with anumber of published analyses. This paper conducts experimentsto examine the sandwich test and the potential to extend it toviscoelastic adhesives since standard viscoelastic testequipment can easily measure three-point bending. The results showthat the stiffness of the sandwich beam is sensitive to thepresence of the adhesive throughout most of the interestingrange for adhesive properties. Second, when tested as afunction temperature and time (or frequency), the stiffness ofthe beam behaves like a classic viscoelastic property. Finally,in the rubbery, elastic range, the shear moduli calculated frombeam tests with thick bonds agreed with those obtained fromtests on bulk samples for adhesives. In the temperature rangewhere the adhesive is hard (glassy behavior), however, problemswere observed for the geometries tested here. Some of theseproblems may be attributable to assumptions made in theanalyses used, and this suggests the need for a new analysisthat addresses these limiting assumptions and extends the testto viscoelastic materials.

adhesives bending epoxy shear modulus superposition viscoelasticity 

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Copyright information

© Kluwer Academic Publishers 2003

Authors and Affiliations

  • Donald Hunston
    • 1
  • Zenichi Miyagi
    • 1
  • Carl Schultheisz
    • 1
  • Shahrooz Zaghi
    • 1
  1. 1.Construction Research DivisionInstitute of Standards & Technology Materials andGaithersburgU.S.A.

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