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Double-Double (DD) laminates are discussed as an alternative to conventional laminates used in aerospace practice, which are usually composed of 0°, 45°, 90°, and −45° plies. Double-Double laminates promise advantages mainly due to simplification of design, optimization, and manufacturing processes. Stacking-sequence independent bending properties of DD laminates allow for significant simplification in context of buckling analysis, as a recent publication shows. However, not all conceivable ply-orientation combinations in DD's building block lead to it. The present short communication outlines briefly how stacking-sequence independent bending properties arise from DD's laminate architecture. The analysis reveals two valid and also a single invalid angle selection, for DD's balanced 4-ply building block. [ABSTRACT FROM AUTHOR]

The use of fiber-metal laminates (FML) allows for substantial advantages over a fuselage skin made of monolithic aluminum materials. Glass fiber prepreg reinforced aluminium is characterized by high damage tolerance capabilities, supporting the structural strength capability in case of any kind of damage. For this reason, FML, and GLARE in particular, have been identified as superior materials for aerospace applications. More than 400m2 FML is applied on each A380, as skin panels and as D-noses for both, vertical and horizontal stabilizer. FML possess the potential to become the baseline material for next-generation single-aisle aircrafts [1, 2, 6].

The Double-Double (DD) laminate family allows for simplification in the context of buckling analysis. Stacking-sequence discussions, known from conventional-laminate optimization, made from 0 ∘ , ± 45 ∘ , 90 ∘ plies, omit for DD. The recently presented DD-specific buckling relation is applied in this article to the 18-panel, 'horse-shoe' laminate blending reference case. The use case addresses the challenge of identifying a compatible group of laminates for differently loaded, adjacent regions, as it is a common scenario in wing covers and fuselage skins. The study demonstrates how the novel DD-laminate buckling relation simplifies the process of determining a buckling optimum for a group of laminates. The process of determining the optimum blended DD panel is presented. Its determined mass is compared with minimum masses, presented in earlier studies, which focus on stacking optimization and blending for more conventional ply orientations and laminate stacking conventions. [ABSTRACT FROM AUTHOR]

Composite structures in aeroplanes are often thin-walled and lightweight, resulting in significant compliance, which presents a handling and assembly challenge due to the associated part deformations. In order to counteract these deformations, the parts are held in their specified geometry using stiff and correspondingly heavy fixtures or jigs. Mobile industrial robots are very versatile and widely used in industrial volume production, but they are limited in their payload capacity. High-rate production of large aerospace modules requires highly automated flexible assembly processes. The approach presented in this paper is to combine mobile units with lightweight assembly jigs that have the capability of deformation compensation. The subject of the study is a high-rate assembly process for flap modules using an Autonomous Industrial Mobile Manipulator (AIMM) and a lightweight end effector. The end effector has a shape compensation function, implemented by an integrated Stewart platform, which enables the compensation of manufacturing tolerances as well as gravity effects. The compensation function is used in a closed loop and counteracts shape deviations by appropriate fixture shape adjustments. The paper reports on the conceptual design of the assembly scenario, the design of the end effector, its realization and the successful experimental demonstration at 1:1 scale. [ABSTRACT FROM AUTHOR]