Composite materials are now a day most frequently used materials in aerospace structures. Mechanically fastened joints are usually used there for joining process due to number of advantages over other conventional joints. These joints are easy to assemble and dissemble and are cheaper. However, they create stress concentration near the hole, leading to source of nucleation and subsequent propagation of cracks under cyclic loading. They also increase weight of the system tat may nullify the advantages we get from composite materials. The present work intent to find fatigue life of two composite laminates usually employed in spacecraft structures. The composites studies are fiberglass reinforced Plastic (FRP) and Carbon Reinforced Plastic (CRP). After preparing the composites, moisture, tension and fatigue tests were conducted on both composites. To know the behavior under damped condition, absorption tests were conducted. Fatigue tests were done both under as plate and butt joint conditions. It was found that in bolted joint condition, both CRP and FRP plates fails in net tension at minimum load but for maximum load they fail in shear.