Structural Scalability Preliminary Studies for the Next Generation Civil Tiltrotor Composite Wing

Abstract

This paper is focused on structural scalability studies of a new generation of civil tiltrotor wingbox structures. Starting from a reference wingbox, developed under the H2020 Clean Sky 2 NGCTR-TD T-WING project, a geometric scaling was performed to upscale the concept up to a larger class tiltrotor named “NGCTR”. Given the wing and the wingbox geometry, a multi-objective optimization, based on genetic algorithms, was performed to find for the NGCTR, among different materials and layups, the best composite wing in terms of weight that satisfies stiffness and crash requirements. The crash requirement plays an important role in regards to wing weight performance. It was found that not all materials investigated in this study succeeded in satisfying both stiffness and crash requirements. The results in terms of minimum structural mass as the target of the optimization process show that the mass ratio of the optimized up-scaled wing is near the geometrical scale factor: 1.58 vs. 1.29. Furthermore, the solution found by the optimizer NGCTR upscaled wing is comparable with other tiltrotor data coming from a literature study. The difference in terms of the ratio between wing structural weight and tiltrotor MTOW is Δ% = +1.4: an acceptable small overestimation of weight compared to a design, optimization, and scalability method that is easily adaptable and effective. The study presented in this work is, in fact, part of a broader activity on scalability and constitutes its first phase, based on low-fidelity models. The scalability study will continue with a further phase (indicated as “phase 2”), in which more reliable models will be set up, allowing a better estimation of the wing’s structural weight and further optimization. The results shown in this manuscript concern phase 1 only and can be considered a starting point at the System Requirements Review level of the up-scaled wing. This phase allowed for a fast exploration of the available solutions by making a first assessment of the main requirements and by aiding in the material choice at the very beginning of the design.