Abstract
The concept of quasi-static crack propagation is used in the present paper to study quantitatively the effects of environmental fluids on fracture in adhesive joints. The mechanisms and mechanics of environmental adhesive fracture under rising loads are discussed. Two types of cracking behaviour were observed. (1) When the dissolution or the “surface energy reduction” mechanism prevailed, the fracture toughness of the adhesive joint in the environment was reduced. (2) However, when environment-enhanced crazes were formed in the adherend at the crack tip region, the local fracture toughness of the adhesive joint would be increased. But cracking was usually unstable so that crack velocities were not readily measurable. Except in so far as the adhesive surfaces may have considerable effects, the fracture toughness of an adhesive joint is independent of the specimen geometries used in the present work. Also, the variation of fracture toughness with crack velocity for an Aluminum/ Araldite joint in a carbon tetrachloride solution is reported.

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