Physical modifications for improved peel strength in a high-temperature epoxy adhesive

The thermal performance of high-temperature thermoset adhesives is invariably gained at the expense of mechanical properties, particularly peel strength. A microscopic study of failure propagation in adhesive joints revealed that fibres within the bondline can affect the fracture path during peel failure in a commercially available modified epoxy adhesive, developed for high-temperature use. This adhesive has been further modified by the incorporation of polymer fibres and the resultant adhesive joints have shown significant increases in peel strength combined with both increases and decreases in lap-shear strength, depending on the fibre orientation. These effects were measured from - 55 degrees C to + 180 degrees C. Improvements were also seen when larger joints, more typical of aerospace structures, were tested. (C) 1998 Elsevier Science Ltd. All rights reserved.