FRACTURE-TOUGHNESS OF SOME ADHESIVE CEMENT SYSTEMS MEASURED IN THE TEMPERATURE-RANGE 20-700-DEGREES-C

The adhesive fracture energy (G//J//C) of several adhesive cement systems has been measured at temperatures extending to 700 degree C using alumina adherends in the double torsion test geometry. Two commercially available low-temperature curing systems were evaluated together with three laboratory-formulated cements, two of which were cured at approximately 1000 degree C. The room temperature values of G//J//C ranged from 0. 6 to 4. 9 J m** minus **2 for the former and from 6. 7 to 11. 4 J m** minus **2 for the latter. Despite the adoption of a linear compliance test geometry it was essential to precrack the specimens in order to obtain 'valid' G//J//C data. Generally the fracture energy of the adhesive cement joints increased with temperature up to a peak between 400 and 600 degree C, and then decreased. The maximum G//J//C value recorded was 40. 2 J m** minus **2. The increase in toughness can be associated with viscous effects in the glassy phases present in the adhesive cements.