The use of large diameter monofilament for improving peel resistance of a brittle high temperature adhesive

Peel force measurements as a function of adherend thickness are reported fo r adhesively bonded specimens based on a cyanate ester resin and aluminium adherends. It has been demonstrated that by incorporating large diameter (0 .28 mm) PTFE monofilament within the adhesive bond then the peel force and associated fracture energy can be increased significantly over that for spe cimens based on adhesive alone. Fracture energy measurements are derived fo r specimens with peeling adherend thickness of up to about 0.6 mm using the 90 degrees peel test. Fracture energies are also derived for peeling of mo re practically-representative 1.6 mm thickness adherends using a single can tilever beam experiment. In-situ photoelasticity and SEM microextensometry experiments are reported which show the stress fields and displacements ass ociated with the presence of the monofilament. It is believed that the repo rted increase in measured fracture energy is partly due to the crack pinnin g effect of the monofilament, and partly due to the monofilament creating a "load shadowed" region between:adherend and monofilament which prevents th e interfacial crack from propagating between adherend and adhesive.