Experiment study of manufacture and performance evaluation in T-stiffened skins with different curvature radii

Abstract For composite T-stiffened skins widely used in the aircraft industry nowadays, the triangle filling area of this structure is the weakest part of compaction quality and mechanical properties. In this paper, T-stiffened skins were prepared by the integral molding process of co-bonding, with a focus on the influence of the tool assembly schemes and different curvature radii on the fiber compaction and tensile strength of the triangle filling area. Three quantitative characteristic parameters of the fiber compaction in the triangle filling area were proposed: stiffener thickness non-uniformity (Hd), fiber volume fraction (Vf) and deformation index (a). The results show that an uneven fiber distribution is found in the inner of the triangle filling area, and the maximum difference of Vf is almost 10%. The deformation index of the triangle filling area is the closest to the theoretical value when rigid tool with triangle flexible tool assembly scheme is adopted. An increase of curvature radius (especially greater than 5mm) causes a decrease of the stiffener thickness non-uniformity, a decrease of the deformation index of the triangle filling area which is close to the theoretical value of 0.5 for the curvature radius of 7mm and 9mm, and an increase of the tensile strength (initial damage load and failure load) of T-stiffened skins under out of plane tensile load with the highest tensile strength for the curvature radius of 7mm.