The Fracture Mechanics of the Pin and Collar Test for High Temperature Anaerobic Adhesives

Abstract A mechanical test method for the studies of high-temperature anaerobic adhesives has been established, based on fracture mechanics, by modifying the standard test method of collar and pin test. Linear Elastic Fracture Mechanics approach was applied to the establishment of the relationship between adhesive fracture surface energy “R”, fracture load and crack length. Hence, from the joints containing a given artificial flaw the adhesive fracture surface energy can be determined; alternatively, from the strength of the joints without artificial flaws the inherent flaw size “ai” can be calculated to account for the decrease of joint strength. The experimental techniques were applied to examine the mechanical behaviour of the joint system based on high temperature anaerobic adhesives. It was found that the joints cured at room-temperature had higher adhesive fracture surface energy but lower joint strength than the joints postcured at high temperatures. The “ai” data explained this interesting phenomenon. The joints cured at room-temperature had extraordinarily large “ai”, which was found to be formed by the uncured adhesive near the edges of the joints and the adhesive further cured in the postcure processes to reduce the “ai”. Also, the growth of intrinsic flaw was found to be responsible for the deterioration of the joints in a short-term, high-temperature ageing process.