Development of a durability test procedure for adhesively bonded composite joints

A significant amount of research has been conducted on the initial bond strength characterization of adhesively bonded composite joints. Improvements in procedures for evaluating bond strength durability of these materials could significantly aid in predicting long-term structural integrity. This study is aimed at developing a durability test procedure that can be used for evaluating the long-term strength durability of adhesively bonded composite joints. An extensive literature review on existing testing procedures for bond strength durability was conducted and conclusions of the advantages and shortcomings of the tests were reached as to their applicability to bonded composite systems. A detailed testing procedure including specimen configuration and fixtures to be used is presented. The procedure includes rapidly aging a set of specimens inside an environmental chamber while being submitted to a fully reversed fatigue load. The specimens are subsequently tested for bond strength using a double cantilever beam test configuration. Results will then be compared with baseline specimens that have not been mechanically fatigued or environmentally aged. The study also includes results from the surface characterization of the specimens prior to bonding using an electrochemical sensor, contact angle and FTIR measurements. Preliminary results of durability are presented and include fracture toughness and mode of failure of the bonds.