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Methodology Development and Validation of WEight Optimized Stiffeners Run-Out Design for Future Composite Wings

Periodic Reporting for period 2 - DOVER (Methodology Development and Validation of WEight Optimized Stiffeners Run-Out Design for Future Composite Wings)

Reporting period: 2019-09-01 to 2021-07-31

DOVER aims to develop a design optimization tool and methodology dedicated to support the design of innovative and weight-optimized composite panel configurations with capability to improve all areas and configuration parameters such as geometries, stacking sequences or anti-peeling fasteners. The resulting methodology accuracy and reliability is to be validated by means of experimental tests. The project will be carried out in a 32-month time span.

DOVER solution proposal is to create and validate a design tool and methodology that enables optimization of wing structural composite panels. The developed tool will provide an environment for the investigation of innovative lightweight shapes including stiffener geometry, thicknesses and lay-ups of different components, shape of the tapering or anti-peeling fasteners configuration. By means of this tool, the designer will be able to predict the failure of any stiffener run-out configuration and obtain a global panel optimization with considerable time savings, because it will not require any complex numerical models to predict behaviour, and economical, because it will not be necessary to carry out expensive testing campaigns.

To achieve this solution, DOVER is structured in different stages that ensure maximum quality, accuracy and reliability. An initial experimental study of stiffener run-out behaviour will establish an experimental base that will be used to develop a model and to generate failure criteria prediction methodology. This methodology will be put in practice by designing different configurations of innovative stiffener run-outs. Optimized solutions will be evaluated and correlated against experimental results. For that, at a final stage, mono and multi stiffener panels will be manufactured, and stress and strain, damage tolerance and fatigue life will be obtained through experimental testing to validate the development.
During this reporting period, Universidad de Sevilla has been working on WPs 1, 2, 3 and also contributing with the management of the project in work package 5.
Related to the testing activity (WP1), Universidad de Sevilla developed a test plan, in which the definition of the test specimens, the impacts that will be carried out on them and the tests to be done are defined. Furthermore, it has been designed, calculated, manufactured and set-up the tooling to make the impacts on the coupons. Also, it has been designed, calculated and manufactured the tooling for the tensile and compression static and dynamic tests. Preliminary impact trials were done on coupons in order to validate the impact tooling and methodology.
Related to the modelling, a methodology for run-out failure prediction has been developed, which is described in the corresponding deliverable (D2.1). This methodology should be corroborated and adjusted with part of the results obtained from the experimental test campaign. Since none of these tests have been performed due to the delay in the provision of the material, it has been impossible to complement the deliverable with an example of its applicability (and it is the reason why it has not been submitted to the platform at the moment of writing this technical report).
During this reporting period Sofitec has been contributing to the development of the specifications for the tests specimens and providing information of the manufacturing for the test plan generated in WP1. The manufacturing activity was defined including all the process parameters and raw materials to be used in coordination with Topic Manager, the materials order was made, tooling for manufacturing was designed and manufactured and finally the specimens for the WP1 test campaign were manufactured and trimmed making a complete set of 8 multi-stiffened (making a total of 32 stringers) panels as part of the task T1.2 following the configurations provided by the Universidad de Sevilla and Dassault Aviation specifications. Sofitec has also carried out the dimensional control of the manufactured specimens. This specimens manufacturing is intended to support the modelling of the stiffeners together with the corresponding tests.
ISSIM has supported the development of the test plan. They have also supported the development of mono-stiffener FE model based on shell elements, which reproduces, with enough precision, the stress magnitudes estimated to be used for the failure criteria, using ANSYS.
Finally, ISSIM has worked on the design of innovative stiffener run-out. All actions related to preprocessing, model creation and establishment of optimization strategies has been accomplished. Subtask depending on test results are pending, as will be explained in section 1.2.
DOVER propose to develop and validate an ambitious and innovative two-stage design optimization
methodology that will provide the aviation industry with the advantage of having an easy-to-implement
tool for obtaining weight-optimized and outperforming composite stiffened panels. With the global and
local models definition independent models of the airframe structure including stiffener, skin, adhesive
layers and core material, will be modelled in a holistic approach that will suppose a step ahead the stateof-
the-art, saving large amounts of time, cost and computational resources compared to the actual, notmethodical
complex strategies followed.
This methodology will be put into practice within the scope of the project to enhance current stiffener runout
standard configurations and optimize them to obtain ground-breaking new lightweight versions to be
included as part of the BizJet Technology Integrated Demonstrator. This advance will be demonstrated
by means of experimental testing at element level, and then up-scaled to the next structural complexity
level (structural detail), which will be also validated experimentally. The weight reduction produced due
to the use of the developed methodology aims to bring different inherent benefits such as fuel saving, cost
reduction or emissions reduction.
DOVER will result in very positive impact for European aeronautic competitiveness and growth in
different ways. It will bring technical impact by introducing innovative design process in aeronautical
industry. It will create economic and environmental impact by achieving reduction on weight, fuel
consumption, emissions and production costs of wing composite panels. This will contribute to
consolidation of future competitiveness and technological leadership of European aerospace industry.
Also, with the collaboration of a reference university in the field of industrial engineering and materials,
DOVER will generate societal impact by transferring part of the obtained knowledge to education field
and bringing design and calculus know-how closer to new generations.
Impact of an stiffened panel