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WING BOX TECHNOLOGY EVALUATION - TRADE-OFF STUDY FOR THE RANKING OF NEW TECHNOLOGIES BEST FITTING WING

Final Report Summary - WINGTECH_EVALUATION (WING BOX TECHNOLOGY EVALUATION - TRADE-OFF STUDY FOR THE RANKING OF NEW TECHNOLOGIES BEST FITTING WING)

Executive Summary:
The overall strategy of the work plan follows a logical progression, whose objective is to satisfy the call text requests: the projects activities have been divided into 4 Work Packages (WPs) that lead to the production of the expected project results:

• WP1 devoted to the development of a baseline model of the advanced wing box stub, which constitute the necessary reference for the following design activities;

• in WP2 different variants developed to analyse the impact of the considered structural modifications on the overall performances of the system: the implementation of Multi-Objective Optimization methodologies is here meant to allow the determination of the best suitable system parameters, within the framework of their variability range and of the existing technological constraints (agreed with the Call for Proposal proponent).

• WP3 bring to the completion of the trade-off study, by allowing the individuation of the most promising technical solutions: the usage of Multi Criteria Decision Making techniques support the final evaluation and selection phase.

The completion of the research project also require minor (but still essential) management activities, which have been grouped into WP4: the management of the project allow the project staff to monitor the progression of the research tasks, to efficiently employ the human and economical available resources and to continuously keep in touch with the CfP proponent.

Project Context and Objectives:
WP1 OBJECTIVE

Definition of the reference FE model: the development of a suitable baseline FE model for the wing box stub provide the necessary basis for the ranking of new technologies (trade-off study) to be carried out.

DESCRIPTION OF WORK

Task 1.1 – FE model development and analysis of the baseline

A FE model of the baseline configuration of the wing stub box developed on the basis of the technical reports and geometrical models (basic master surfaces) provided by the CfP proponent: this baseline FE model analysed under the given load cases and evaluated with respect to the relevant figures of merit (weight, strength, stiffness, buckling behaviour, etc.).

Activities (involved partners):

▪ examination of the data received from the CfP proponent: master surfaces, other technical inputs (ES);

▪ first baseline FE model creation (ES);

▪ first batch FEM analyses under the given load cases (ES).

Task 1.2 – Model modification to reach an agreed refinement level

The first developed FE model suitably modified (in agreement with the CfP proponent) to reach a satisfactory level of refinement: a final set of FE analyses will be performed on the refined model, which constitute the starting point for the following trade-off study to be carried out.

Activities (involved partners):

▪ design modification to reach a refinement level agreed with the CfP proponent (ES);

▪ FEM analysis of the refined model under the given load cases (ES);

▪ completion of the WP outputs: baseline model + report (ES).

DELIVERABLE

D1 – Baseline FE model and analysis report of the advanced wing box stub

Deliverable D1 comprise the following outputs:

•D1.a – the FE model of the wing box;

•D1.b – the sub-models of relevant components or parts;

•D1.c – a complete report, documenting model features and analyses results.

WP2 OBJECTIVE

Evaluation of the models variants: a set of new configurations for the wing stub box developed and analysed in order to provide the data necessary for the final comparison phase.

DESCRIPTION OF WORK

Task 2.1 – Development and analysis of the FE models of the advanced wing stub box configurations

A set of FE models of the wing stub box developed, considering different structural solutions and incorporating a defined set of new technologies, which selected by the CfP proponent: the models consider different structural configurations, in particular for the spars, the ribs and the outer skin panels; moreover, each configuration generate model sub-variants depending on the material/layer/multilayer technology selected and on the repair concept adopted for the outer panels.
The analyses based on a given set of relevant load cases: the performances of the different solutions evaluated on the basis of the chosen merit figures (weight, strength, stiffness, buckling behaviour, etc.). In order to guarantee the individuation of the best possible project designs (given the structural alternatives provided by the CfP proponent, the existing constraint and the design objectives), a multi-objective optimization methodology implemented, which allow the best exploitation of the features of the new technologies taken into account.

Activities (involved partners):

▪ development of a number of FE models considering different structural solutions, to be agreed with the CfP proponent (ES);

▪ first batch analysis of the developed FE models under the given load cases (ES).

Task 2.2 – Refinement of the advanced wing stub box configurations

After the evaluation of the results of the performed analyses, the developed models will be suitably refined: a final set of FE analyses performed on these refined configurations, in order to provide the information necessary the following phase (WP3), which provide the final results of the trade-off study.

Activities (involved partners):

▪ iterative analyses devoted to the achievement of:

o the best possible geometrical parameters, regarding each of the considered design configurations, by means of a multi-objective optimization methodology (ES);

o the desired refinement level of the developed Fe models (ES);

▪ completion of the WP outputs: developed models (Ansys) + report (ES).

DELIVERABLE

D2 – FE models and analysis report of all the design variants
Deliverable D2 comprise:

•D2.a – the FE models of all the design variants of the wing box;

•D2.b – the sub-models of relevant components or parts;
•D2.c – a complete report, documenting model features and analyses results.

WP3 OBJECTIVE

Selection of the most promising structural solution for the wing proof test articles to be subsequently tested.

DESCRIPTION OF WORK

Task 3.1 – Comparison of the developed variants

The trade-off study finalized comparing the different variants of the design, in terms of the agreed figures of merit: the most promising solutions of the wing stub box, for which designs of some further structural details developed, selected in agreement with the CfP proponent.

In order to support the interpretation of the collected data, allowing the selection of the most promising design solution (in presence of numerous and possibly conflicting considerations), the most advanced techniques devoted to Multi Criteria Decision Making (MCDM) implemented.

Activities (involved partners):

▪ comparison of the analysed design alternatives, in terms of the considered merit figures, in agreement with the CfP proponent (ES).

Task 3.2 – Development and analysis of the detailed models of the most promising solutions

The most promising configurations (selected within the Task 3.1) further refined, by modelling adequate structural details (such as component interfaces, openings, fittings and local reinforcements). These configurations finally analysed under the given load cases and the results evaluated with respect to the relevant figures of merit (weight, strength, production, maintenance, etc.).

Activities (involved partners):

▪ development of FE models characterized by the presence of all the necessary structural details (ES);

▪ completion of the WP outputs: refined FE models (Ansys/Nastran) + report (ES).

DELIVERABLE

D3 – Refined FE models and trade-off report

Deliverable D3 will comprise:

•D3.a – the FE models of the relevant structural details;

•D3.b – a complete report, documenting the FE analyses results;

•D3.c – a final report documenting the results of the performed trade-off study.

Project Results:
In line with the aims of Wingteh_Evaluation, the result of the trade-off on the wing box made it possible to select and verify a candidate optimal configuration to be used for the subsequent phases within the Clean Sky project.

The variants of the wing box analyzed with classical structure in aluminum were penalized in terms of total weight reached in front of a mechanical behavior comparable. Among the variants in composite material, analysis has highlighted the differences in behavior with respect to the number of ribs, the number of spars and definition of the composite in terms stack.
As the final result of the project, a configuration of composite materials has been identified that -with respect to the initial reference configuration- maintaining similar deflections and improving the structural usage factor allowed a weight reduction of 25%.
The Wingteh_Evaluation project allowed to highlight the feasibility and efficiency of an automated process flow that, starting from some basic topological configurations, allows of fully automatic regeneration of the entire finite element model of the wing box, the related analysis under the action of design loads and the evaluation of results and structure’s merit parameters.
It is therefore particularly easy to explore in a systematic way a large number of potential interesting configurations, gradually discarding the less performing (in terms of weight, strength, stifness, buckling behavior) until the identification of the optimal one.
The methodology is valid reference, which can be extended to other contexts where it is of interest the optimization of structures formed by panels and beams reinforcement.

Potential Impact:
The project results produce important impacts, introducing in the wing components technology fundamental innovations that bring to the attainment of significant technical, economic and environmental benefits at European level.
The core of this project is in fact the development of a trade-off study, meant to compare several different structures incorporating new technologies, in order to determine the most promising solutions among those considered: these different solutions compared on the basis of suitably selected merit figures, whose aim basically the lowering of the weight of the structure, the enhancement of its mechanical properties (in terms of strength, stiffness, buckling behaviour) and the reduction of the costs and efforts due to the production and maintenance phases of the considered components.
It is apparent that the achievement of such results contribute to the following positive impacts:
▪ increased systems performance: improved characteristic of the airplane structural components will allow higher reliability (therefore elongated grounding and inspection intervals) and lower structural weight (therefore lower fuel consumption and/or improved transport capacity): this will lead to a better buy-to-fly ratio, which will improve the European situation against competitors in the US and the Far East;
▪ increased safety: the use of high strength structural components will reduce the risk for high local stress peaks, responsible for crack growth and component failure;
▪ positive economic impacts: the analysis of different alternative approaches for the manufacturing of structural components will allow to exploit at maximum the advantages given by the considered technologies;
▪ decrease of environmental impacts: the improvement of performances and the weight reductions in the aerospace industry will contribute to a substantial reduction of CO2 emissions;
▪ competitiveness of EU industry: the project is meant to contribute to the transformation of the European industry from a resource intensive to a knowledge-based one; the skilled workforce, together with the knowledge stemming from the project, will enhance the competitiveness of European industry in comparison to the resource intensive approaches still pursued other markets.
The objectives of the project are hence fully in line with the current legislation activities (regarding CO2 emission, pollution, hazards, etc.), with the general market pull (durability, safety, efficiency, etc.) and with specific aerospace market pull (stringent requirements for increased economy, fuel reduction, greenhouse gases reduction, etc.).