The study of failure mechanisms associated with adhesively bonded composite joints has seen shifts towards smaller and smaller scales in the last decade. Understanding the long term strength of bonded systems is a key element in obtaining acceptance from the bonded composite community, particularly in the aerospace industry. Imperfections including contamination in an adhesive bond can affect its performance, leading to premature failure of the bonded structure. These imperfections often cannot be detected by conventional non-destructive inspection methods, and understanding the effect of undesirable bonding conditions (contamination) on the bond strength is critical. In this study, a procedure is developed to produce adhesive bonds of various strengths as a result of localized contamination. The change in surface chemistry as a result of contamination is studied using Fourier transformed infrared spectroscopy and EDS spectroscopy. Bond strength and mechanisms of fracture are investigated at the macro-scale via double cantilevered beam testing and at the micro scale via end notch fracture testing. This multiscale approach aids in understanding mechanical performance of a bonded joints and their fracture properties. Additionally, development of an approach to quantify failure modes using via digital imaging processing is demonstrated and is correlated with fracture properties.
