### Parametric Set-Up of a Structural Model for FERMAT Configuration Aeroelastic and Loads Analysis

*Thomas Klimmek*

#### Abstract

The development of a structural finite element model for the generic aircraft configuration named FERMAT is presented. The geometry of the FERMAT configuration is based on the NASA Common Research Model (CRM). The CRM is a wing/body/nacelle/pylon/horizontal-tail configuration was originally developed for the the AIAA 4th Drag Prediction Workshop in 2009. It is based on a long-range, wide-body transonic transport.

As far as the CRM is missing the vertical stabilizer as well as other well as the definition of overall aircraft characteristics, they are defined for the FERMAT configuration.

For the development of the structural model a parametric modeling approach is applied, using methods from Computer Aided Geometric Design (CAGD). A design process is established, comprising the parametric modeling part, loads analysis, and the sizing of the structure considering structural and aeroelastic constraints. The parametric approach enables a wide range of variations while the the structural model for the wing-like components is as detailed as possible. The parametric design loop has three basic sequential steps. It starts with the set-up of parameterized simulation models (e.g. finite element model, aerodynamic model, mass models, and optimization model) for the given target flight shape. It follows an aeroelastic loads analysis using the condensed structural model for selected mass cases. And finally, the structural components are sized independently using the detailed structural models, where for the wing also aileron effectiveness is defined as constraints. After adapting the jig shape of the wing, the process is repeated until the structural sizing and the jig-shape converge.

The structural dynamic characteristics are presented for two mass cases. The final flutter investigation is briefly described wherein advantage was derived from the parametric approach. In order to avoid the first flutter mode to be at the horizontal stabilizer, the structural concept of the load carrying structure of the horizontal stabilizer was modified and the design process repeated.

As far as the CRM is missing the vertical stabilizer as well as other well as the definition of overall aircraft characteristics, they are defined for the FERMAT configuration.

For the development of the structural model a parametric modeling approach is applied, using methods from Computer Aided Geometric Design (CAGD). A design process is established, comprising the parametric modeling part, loads analysis, and the sizing of the structure considering structural and aeroelastic constraints. The parametric approach enables a wide range of variations while the the structural model for the wing-like components is as detailed as possible. The parametric design loop has three basic sequential steps. It starts with the set-up of parameterized simulation models (e.g. finite element model, aerodynamic model, mass models, and optimization model) for the given target flight shape. It follows an aeroelastic loads analysis using the condensed structural model for selected mass cases. And finally, the structural components are sized independently using the detailed structural models, where for the wing also aileron effectiveness is defined as constraints. After adapting the jig shape of the wing, the process is repeated until the structural sizing and the jig-shape converge.

The structural dynamic characteristics are presented for two mass cases. The final flutter investigation is briefly described wherein advantage was derived from the parametric approach. In order to avoid the first flutter mode to be at the horizontal stabilizer, the structural concept of the load carrying structure of the horizontal stabilizer was modified and the design process repeated.

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ISSN 1974-5117