Environmental and chemical degradation of carbon/epoxy lap joints for aerospace applications, and effects on their mechanical performance

Composite structures in service are typically subjected to different environmental conditions, which may affect their mechanical performance as well as their flammability potential. This study investigates the degradation encountered by lap joints made with woven carbon/epoxy and epoxy-based adhesive, treated in water or anti-icing additive or jet fuel or hydraulic fluid. Gravimetric tests were carried out, and degradation was observed with changes in color, mass, microscopic features and mechanical properties, with the support of statistics. This investigation proves that the performance of the epoxy-based structural adhesive deteriorates considerably when the adhesive is contaminated by hydraulic fluid and anti-icing additive, while the carbon/epoxy weave appears affected by anti-icing additive at a lesser rate.