On the use of double-double design philosophy in the redesign of composite fuselage barrel frame components

The use of optimization procedures can provide a valuable contribution in optimizing the laminate design of composite components for mass minimization and mechanical performance maximization. Design for weight and strength requirements of composite structures can be efficiently provided with the newly developed double-double laminates concept, which allows to overcome the conventional 0, 90, and ±45° ply orientations and symmetry requirements in laminates. In the double-double designed components, composite laminates are made up stacking thin sub-laminates with four [±Φ, ±Ψ] oriented plies without symmetry requirements. In the present paper, the lay-up and thickness profile of the composite frames in a fuselage section have been redesigned according to the double-double design concept taking into account the operating loads. The starting quad configuration has been replaced by an optimized double-double configuration with suitable lay-up and thickness profile for each of the frames, while achieving a reduction in the total components mass. Highlights: Double-double laminates offer a novel approach to composite laminate design. Double-doubles aim to simplify design with composites as with metals. Laminate optimization performed varying plies orientations and number. Double-double design of components optimized with respect to the acting loads. In aviation double-doubles allow lightening of composite laminate components.