Abstract

Abstract The two tests of most importance in evaluating structural adhesives for metals are (1) lap shear strength and (2) peel strength. Epoxies perform well in the first due to high tensile and shear strength. They are poor in the second unless modified to reduce brittleness. We have developed a urethane modified epoxy for this purpose. By taking climbing drum peel data in which both the temperature and the peel rate are varied, the time-temperature superposition principle can be tested. This principle is most generally applicable to thermoplastic materials between Tθ and Tθ + 100 °C (Tθ = glass transition temperature), and serves as a measure of viscoelastic response in the polymer. First, good agreement was found for a thermoplastic adhesive (PE-AA film). This was done to verify that climbing drum peel data can be used in this manner. Next, data were taken for our urethane modified epoxy. Results showed adherence to the superposition principle only above the heat distortion temperature of the cured po...

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