Search Results (4)

This paper presents a methodology that involves the development of high-fidelity modeling and simulation procedures aimed at supporting virtual certification for crashworthiness requirements specific to tiltrotor aircraft, addressing the critical need for accurate safety requirement fulfillment predictions and weight containment of wing. The unique crashworthiness requirement for tiltrotor wings necessitates a design that can ensure a controlled failure during survivable crash events. This is to alleviate the inertial load acting on the fuselage, thereby protecting occupants from injuries and fire while ensuring the integrity of escape paths. The objective of this methodology is to simulate the crash effects on the entire wing using explicit, non-linear, and time-dependent FE analysis. This approach verifies the spanwise placement of the frangible sections, the mode of failure, the loads acting on the fuselage links, and the acceleration transmitted to the structure. This study focuses on a standalone analysis. Full article

The T-WING project, a CS2-CPW (Clean Sky 2 call for core partner waves) research initiative within FRC IADP (Fast Rotor-Craft Innovative Aircraft Demonstrator Platform), focuses on developing, qualifying and testing the new wing of the Next-Generation Civil Tilt-Rotor (NGCTR). This paper introduces a case study about a methodology for refining the stick-beam model for the NGCTR wing, aligning it with the GFEM (Global Finite Element Model) wing’s dynamic characteristics in terms of modal frequencies and mode shapes. The initial stick-beam model was generated through the static condensation of the GFEM wing. The tuning process was formulated as an optimization problem, adjusting beam properties to minimize the sum of weighted quadratic errors in modal frequencies and Modal Assurance Criterion (MAC) values. Throughout the optimization, the MAC analysis ensured that the target modes were tracked, and, at each iteration, a new set of variable estimates were determined based on the gradient vector and Hessian matrix of the objective function. This methodology effectively fine-tunes the stick-beam model for various mass cases, such as maximum take-off weight (MTOW) and maximum zero-fuel weight (MZFW). Full article

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. Full article

The main objective of this paper is to describe a methodology to be applied in the preliminary design of a tiltrotor wing based on previously developed conceptual design methods. The reference vehicle is the Next-Generation Civil Tiltrotor Technology Demonstrator (NGCTR-TD) developed by Leonardo Helicopters within the Clean Sky research program framework. In a previous work by the authors, based on the specific requirements (i.e., dynamics, strength, buckling, functional), the first iteration of design was aimed at finding a wing structure with a minimized structural weight but at the same time strong and stiff enough to comply with sizing loads and aeroelastic stability in the flight envelope. Now, the outcome from the first design loop is used to build a global Finite Element Model (FEM), to be used for a multi-objective optimization performed by using a commercial software environment. In other words, the design strategy, aimed at finding a first optimal solution in terms of the thickness of composite components, is based on a two-level optimization. The first-level optimization is performed with engineering models (non-FEA-based), and the second-level optimization, discussed in this paper, within an FEA environment. The latter is shown to provide satisfactory results in terms of overall wing weight, and a zonal optimization of the composite parts, which is the starting point of an engineered model and a detailed FEM (beyond the scope of the present work), which will also take into account manufacturing, assembly, installation, accessibility and maintenance constraints. Full article