Measuring the mode I adhesive fracture energy, GIC, of structural adhesive joints: the results of an international round-robin

The results of an inter-laboratory round-robin test programme designed to validate a new protocol for determining the mode I adhesive fracture energy, G IC, of structural adhesive joints are presented. The analysis schemes employed by the protocol are described and critically compared in the light of these results. The importance of a number of validity checks on the data analyses are discussed and the accuracy and precision of the test method is determined according to existing International standards. The values of G IC deduced were shown to be independent of the test geometry of the joint (i.e. DCB versus TDCB) but dependent upon the substrate material used. Additional studies have shown that the substrate dependence was due to the cured adhesive in the different joints possessing different values of glass transition temperature.