Constant Displacement Rate Method for Testing Epoxy Adhesive Bonds

Abstract A constant load-point displacement rate method is used to test double-cantilever-beam specimens of 2024-T3 aluminium alloy bonded with AF126 adhesive. The elastic energy release rate, G1, was calculated from measured values of load and load-point displacement. Measurements in humid air at 50°C showed that G1 depended strongly on load-point displacement rate. At high rates, the bond was not degraded and G1 was equivalent to G1c. At very low rates, the bond was degraded and G1 was equivalent to G1scc. In a region between these extremes, G1 was sensitive to load-point displacement rate because moisture degraded the bond at a rate similar to the crack velocity. Selection of data where G1 was unstable with load-point displacement rate leads to a crack velocity, which may be used as a bond durability indicator.