The Fatigue and Durability Behaviour of Automotive Adhesives. Part II: Failure Mechanisms

Abstract In part I [1] a fracture mechanics approach has been successfully used to examine the cyclic fatigue behaviour of adhesively-bonded joints, which consisted of aluminium-alloy or electro-galvanised (EG) steel substrates bonded using toughened-epoxy structural paste-adhesives. The adhesive systems are typical of those being considered for use, or in use, for bonding load-bearing components in the automobile industry. The cyclic fatigue tests were conducted in a relatively dry environment, of 23°C and 55% RH, and in a “wet” environment, namely immersion in distilled water at 28°C. The “wet” fatigue tests clearly revealed the significant effect an aggressive, hostile environment may have upon the mechanical performance of adhesive joints, and highlighted the important influence that the surface pretreatment, used for the substrates prior to bonding, has upon joint durability. The present paper, Part II, discusses the modes and mechanisms of failure for the two adhesive systems in both the “dry” and “...