For their several significant advantages, the composite structures are fast gaining their popularity as an effective structural component over their metallic counterparts. In recent years the glass fiber reinforced polymers (GRP), specially glass/epoxy composites are widely applied in several civil engineering applications ranging from seismic retrofit of columns and strengthening of walls, slabs, to new building frames and even bridges. It is also well known that there is a degradation of material property during its service life, as it is often subjected to environments with high temperature and humidity or having a sharp rise and fall of temperature (thermal spikes). The deterioration that occurs in FRP during the service life is in general, linked to the level of moisture that is absorbed. The absorption of moisture can be attributed largely to the affinity for moisture of specific functional groups of a highly polar nature in the cured resin. The absorption of moisture causes plasticization of the resin to occur with a concurrent swelling and lowering the glass transition temperature of the resin. In this work, the specimens were tested for their UTS, FS and ILSS for every 120 hours intervals and studied degradation pattern of Carbon FRPs (CFRPs) when exposed to alkaline solution. Thus, the composite system that absorbed more moisture (Iso-polyester/carbon) showed poor mechanical properties. The percentage drops in mechanical properties is due to moisture absorption which lead to swelling in composites as well as delamination between fiber and matrix. Alkali environment causes CFRPs embrittlement and micro cracks of resin, longitudinal and transverse mechanical properties show a significant decrease. Carbon/epoxy proved superiority over vinylester/carbon and Iso-polyester / Carbon, in terms of lower values of degradation in UTS, Flexural Strength and ILSS specimens

Keywords: Alkaline solution, FRP, SEM, Degradation Studies