A bond test is used to determine the ability of an adhesive to remain in contact with a surface or material while under stress or the adhesive’s ability to hold together two materials as they are stressed. The bond itself is tested after it has been applied and allowed to cure by either applying a force directly to the adhesive in an attempt to remove it from the material or by attempting to separate to materials to have been connected to each other by the adhesive. The force is then either steadily increased or remains constant and is applied to the bond until it fails.
Purpose of Bond Testing:
Bond tests determine an adhesives’ bond strength. The bond strength of a material may be considered to be its overall “stickiness” and will depend on the type of stress the bond experiences and the temperature at which the test is run. This strength will also depend upon the direction of the force applied to the bond. For example a bond may require more force to be broken in shear than in direct tension.
Types of Bond Tests:
There are many different types of bond testing, but the most commonly performed are tensile, shear and peel testing with torsional, impact, and pull-off tests performed less often. Each bond test is used to determine the adhesives bond strength in a given direction or under a given type of stress. Nearly all bond testing will take one of two forms. Either the adhesive will be applied to the surface of a material as a type of coating and the adhesives’ bond strength is determined to be its ability to remain in contact with the material while under stress or the adhesive is applied between two rigid substrates and its bond strength is determined as its ability to hold the two substrates together while under stress.
Types of materials:
Generally a bond test is performed on an adhesive; however this adhesive can consist of a wide range of materials or come in several forms. The more popular types of adhesives that undergo bond testing are composed of polymers, composites, grouts, mortars, and glues. These adhesives may be applied to all types of materials but are often tested when adhered to metals, plastics, ceramics, woods and dental materials (e.g. dentine and enamel). The adhesive is generally tested when bonded between two rigid substrates, but may also be tested when applied as a coating or as the bonding material between a flexible coating and a rigid substrate.