Development of a Nondestructive Method for Ultrasonic Evaluation of Adhesive Bond Joint Performance

Abstract

Adhesives are a group of substances with chemical composition and structure specially formulated for joining the surfaces of materials together. These substances are generally applied to specific areas of substrate materials that are to be bonded in order to fabricate an assembly. The region between the two or more substrate materials being joined together by the adhesive, including the surface interfaces, is the adhesive bond joint (ABJ). Irrespective of the chemical nature and of the mechanisms of adhesion in a bonded assembly, the adhesive material is usually a thin layer between two substrate surfaces of the components of the assembly. The components of the assembly and the adhesive material are generally composed of materials that are substantially different in many of their physical, chemical and mechanical characteristics. Therefore, regardless of the chemical composition of the adhesive and adherent materials, all ABJ’s are multilayered structures, composed of highly inhomogeneous materials, in which the adhesive must contribute to the structural integrity of the whole assembly. In other words, the adhesives are not just a means of joining structural elements, but are load-bearing components of structural systems; therefore their failure could cause the structure to fail.