Rapid transformation of lamination parameters into stacking sequences

Lamination parameter optimisation is a highly efficient type of composite optimisation. An equally efficient transformation of lamination parameters into stacking sequences is not yet available. This paper presents a general method for rapidly transforming lamination parameters into continuous stacking sequences. Systematic studies of the relationship between lamination parameters and stacking sequences provide a broad understanding of the transformation problem. An important finding is that multiple stacking sequences share the same lamination parameter set. The transformation is therefore not unique and has to account for multiple layup solutions. The layup retrieval algorithm uses primitive optimisation techniques to search for all optima in the layup space. Ply angles and layer numbers are hereby not restricted. In two representative examples, the authors show the algorithm's capabilities of finding all stacking sequence solutions of a twelve layer laminate and of finding multiple stacking sequence solutions for arbitrary layer numbers. This makes the algorithm applicable for stacking sequence retrieval, the last step in lamination parameter optimisation

Lightworks, a scientific research framework for the design of stiffened composite-panel structures using gradient-based optimization

Efficient structural optimization remains integral in advancing lightweight structures, particularly concerning the mitigation of environmental impact in air transportation systems. Varying levels of detail prove useful for different applications and design phases. The lightworks framework presents a modular approach, for the consideration of individual design parameterizations and structural solvers for the numerical optimization of thin-walled structures. The framework provides the combination of lightweight fibre composite design and the incorporation of stiffeners for a gradient-based optimization process. Therefore, an analytical stiffener formulation is implemented in combination with different continuous composite material parameterizations. This approach allows the analysis of local buckling modes, as well as the consideration of load redistribution between stringer and skin. The flexibility achieved in this way allows a tailored configuration of the optimization problem to the required level of complexity. A verification of the framework's implementation is carried out using established literature results of a simplified unstiffened wing box structure, where a very good agreement is shown. The accessibility of solvers with different fidelity through a generic solver interface is demonstrated. Furthermore, the usage of the implemented continuous composite parameterizations as design variables is compared in terms of computational performance and mass, providing different advantages and disadvantages. Finally, introducing stringer into the wing box use case demonstrates a 38% mass reduction, showcasing the potential of the inline optimization of stiffeners

The Suction Panel - xHLFC and Structural Solution for Energy Efficient Aviation

Future energy-efficient aircraft requires a further drastic reduction in drag and weight. Is it contradictory to improve both at the same time? Is it possible to design a highly efficient HLFC system to be weight-neutral? The present study, performed within the Cluster of Excellence SE2A – Sustainable and Energy-Efficient Aviation, summarizes aspects and considerations of the contributing disciplines to derive a solution for a suction-based system on short-range aircraft wings with maximum efficiency, i.e. hybrid laminar flow control application capabilities at minimum weight penalty. Several new features – novel wing design and simulation tools, the potentials of thin plies for weigth saving and the 3D-printing possibilities for ventable core structures – are investigated to achive this goal

Structural Optimisation of an Aircraft Wing using rapid Analytical Methods

The investigation of new aircraft designs requires robust and rapid evaluation methods on a physical basis allowing to explore the unknown design space. The structural optimisation of aircraft wings is particularly challenging due to aeroelastic coupling efects. The minimum structural mass of an aircraft wing with a given outer shape can only be found in a multi disciplinary optimisation including structural and load calculations. In this thesis a structural optimisation framework for wing-like structures is developed. Material formulations based on lamination parameters allow the usage gradient based optimisation algorithms. The modular optimisation framework provides a general interface to structural solvers enabling a multi-fidelity optimisation process. In this thesis the structural solver PreDoCS calculates internal structural loads with an analytical cross-section theory in combination with one dimensional finite beam elements. Outer loads are provided by external tools and imported through the standardised CPACS interface, allowing multi disciplinary coupling. A comparison of the optimisation results of PreDoCS and a finite element based structural solver establishes confidence in the framework. The optimisation of a mid range aircraft wing shows the potential of lamination parameter optimisation with a gradient based, analytical optimisation framework

Actuated Adaptive Wingtips on Transport Aircraft: Requirements and Preliminary Design Using Pressure-Actuated Cellular Structures

Folding wingtip technologies are in the focus of research for their potential to significantly reduce the induced drag of transport aircraft by increasing the wing’s aspect ratio in flight. While state of the art commercial aircraft, such as the Boeing 777X, are equipped with on-ground folding wingtips, manufacturers further develop in-flight folding wingtip technology by adding aeroelastic hinges for load alleviation such as in Airbus’ AlbatrossONE project. This paper systematically analyses wingtip functionalities, including wingtip folding, load alleviation, mission adaptability and roll control, collects them in a requirement list and derives design features from this list. The authors develop the identified features into a design for actuated adaptive wingtips based on pressure-actuated cellular structures, allowing in-flight morphing of the wingtips while withstanding significant aerodynamic loading. This study characterises the actuator’s maximum deformation and load-bearing capacity within the entire operating envelope, restricted by structural stresses. In contrast to existing folding wingtip technologies, actuated adaptive wingtips can be actively controlled in flight and simultaneously show significant stiffness adaptivity. The actuator’s stiffness profile identified in this paper and provided in mathematical equations forms the basis for the actuator’s aeroelastic characterisation. The stiffness profile can further be used to investigate the actuator’s capability of roll control, load alleviation and mission adaptability

Mechanical testing of threaded inserts for additively manufactured sandwich panels with Gyroid core structures

Additively manufactured sheet networks with low relative density show significant load-bearing capabilities while fulfilling additional requirements such as conducting gases. Introducing sheet networks as a core structure in sandwich panels requires fastening points for panel installation. This study develops, manufactures and mechanically investigates fastening points for triply periodic minimal surface sheet networks. While two concepts for Gyroid sheet networks are derived from an existing Honeycomb concept, a third concept improves the load-to-weight ratio by functionally grading the Gyroid's relative density. Pull-out tests were conducted to compare the performance of the insert concepts integrated into the Honeycomb and Gyroid sandwich specimens. The tests showed that only the functionally graded Gyroid concept reaches a significantly higher load-to-weight ratio than the Honeycomb concept, suggesting that its modified structure is effective. A numerical comparison of the Honeycomb's and Gyroid's unit cells shows equal moments of area for equal relative densities, thereby underlining the same load-bearing capabilities for similar insert concepts. In contrast to the Honeycomb fastening points, the Gyroid fastening points show a significant load-bearing capacity after the initial failure, which results in a residual load-bearing capability and, therefore, increased system robustness

Mechanical testing of threaded inserts for additively manufactured sandwich panels with Gyroid core structures

Additively manufactured sheet networks with low relative density show significant load-bearing capabilities while fulfilling additional requirements such as conducting gases. Introducing sheet networks as a core structure in sandwich panels requires fastening points for panel installation. This study develops, manufactures and mechanically investigates fastening points for triply periodic minimal surface sheet networks. While two concepts for Gyroid sheet networks are derived from an existing Honeycomb concept, a third concept improves the load-to-weight ratio by functionally grading the Gyroid's relative density. Pull-out tests were conducted to compare the performance of the insert concepts integrated into the Honeycomb and Gyroid sandwich specimens. The tests showed that only the functionally graded Gyroid concept reaches a significantly higher load-to-weight ratio than the Honeycomb concept, suggesting that its modified structure is effective. A numerical comparison of the Honeycomb's and Gyroid's unit cells shows equal moments of area for equal relative densities, thereby underlining the same load-bearing capabilities for similar insert concepts. In contrast to the Honeycomb fastening points, the Gyroid fastening points show a significant load-bearing capacity after the initial failure, which results in a residual load-bearing capability and, therefore, increased system robustness

Actuated adaptive wingtips on transport aircraft: Requirements and preliminary design using pressure-actuated cellular structures

Folding wingtip technologies are in the focus of research for their potential to significantly reduce the induced drag of transport aircraft by increasing the wing’s aspect ratio in flight. While state of the art commercial aircraft, such as the Boeing 777X, are equipped with on-ground folding wingtips, manufacturers further develop in-flight folding wingtip technology by adding aeroelastic hinges for load alleviation such as in Airbus’ AlbatrossONE project. This paper systematically analyses wingtip functionalities, including wingtip folding, load alleviation, mission adaptability and roll control, collects them in a requirement list and derives design features from this list. The authors develop the identified features into a design for actuated adaptive wingtips based on pressure-actuated cellular structures, allowing in-flight morphing of the wingtips while withstanding significant aerodynamic loading. This study characterises the actuator’s maximum deformation and load-bearing capacity within the entire operating envelope, restricted by structural stresses. In contrast to existing folding wingtip technologies, actuated adaptive wingtips can be actively controlled in flight and simultaneously show significant stiffness adaptivity. The actuator’s stiffness profile identified in this paper and provided in mathematical equations forms the basis for the actuator’s aeroelastic characterisation. The stiffness profile can further be used to investigate the actuator’s capability of roll control, load alleviation and mission adaptability