The Effect of Isothermal and Hygrothermal Ageing on Mechanical Properties of Glass/Epoxy Composites and Fiber Metal Laminates

The major aim of this study is to investigate the effects of isothermal and hygrothermal ageing on mechanical properties of fiber metal laminates (FMLs) and glass/epoxy (GE) composites. Both the glass/epoxy composites and FML specimens fabricated using wet lay-up technique, were subjected to isothermal ageing (130 °C, dried air) and hygrothermal conditioning (90 °C, immersed in distilled water) for up to 5 weeks. The degradation of mechanical properties due to two types of aging was evaluated by the flexural and Charpy impact testing. Experimental results revealed that the flexural properties of both the glass/epoxy composites and FMLs were significantly affected by the hygrothermal aging, whereas a lower level of deterioration in impact strength was found. On the other hand, the impact strength was severely affected by the isothermal aging in the form of reduced ductility and embrittlement, while no significant reduction was found in stiffness of both the isothermally aged flexural FML and glass/epoxy specimens.