Fatigue characterization of adhesive joints in aeroplanes – the development of a negative load ratio (R < 0) testing method

Abstract

Adhesive joints are an efficient method to transfer high loads between structural components. High-performing adhesive joints require careful design and precise knowledge of the adhesive product used. Especially in aeroplanes, load spectra range from negative to positive load (factor) levels. It is well known that the trajectory of crack growth in adhesive joints is highly sensitive to local stress state and fracture toughness. However, up to date, there are no methods to accurately study fatigue of adhesive joints under varying load (positive-to-negative loading, i.e., load ratio R changing its sign). In this study, a testing system is developed to perform negative R fatigue testing of adhesive joints and mode II crack propagation