Of great interest to manufacturers of rubber-to-metal bonded assemblies is bond strength and bond durability. Bond strength is the ability of the assembly to stick together while durability refers to how long the bond will last in a given environment. These environments can include water immersion, acid and alkali exposure, salt spray, oil and fuel resistance, heat and cryogenic resistance, dynamic cycling, as well as a vast array of other environments.

The best test is to make the part and test it under actual conditions. Most engineering companies use a simulating test that may accelerate the failure. The accelerated test gives an indication as to the life expectancy of the bonded part or at least be able to discern between various adhesives.

The American Society for Testing and Materials International (ASTM International) and the International Organization For Standardization (ISO) are two organisations that have test methods for measuring bond strength. These standards describe a method to make test pieces that can be peel tested, or tested in tensile or shear (see Table 6).

The bonded test specimen can often be placed in various environments (with or without stress) for testing beyond primary bond strength. By using such...