The research work described in this proposal involved a detailed simulation of the acoustic performance of CFRP nose fuselage design, and a comparative analysis of a conventional metallic design.
The physical properties of CFRP structural components gives a different vibroacoustic response compared to metallic structures. In particular the low material damping and reduced number of mechanical joints made possible by CFRP technologies can give rise to higher noise levels in the cockpit.
The work used the software package VA One, which is capable of simulating the response of vibroacoustic systems across the full frequency range. In this project AOES proposed to use the FEF/FEM and FEM/BEM capabilities of VA One. AOES already possessed a license for the VAOne software and has engineers trained in its use.
It was expected that the acoustic noise assessment conducted in this project will form input to the Topic Manager and/or ITD leader for improving the design of the fuselage nose and cockpit for superior acoustic performance.
First activity in the project after having received the data package from Topic Manager containing a CAD and FE model of the baseline cockpit, was to align both models, adapt where needed and write a conformity report about how they align.
Based on this report, it was decided to add more detail to the models and to not use the delivered FEM as the baseline. In this second step the delivered CAD was used as baseline.
To be able to make a more detailed mesh, it was important that the delivered CAD was refined and adapted (“fixed”) so that a more automatic mesh approach could be used. This automation was essential because of the vast amount of elements that would make manual efforts impossible from a schedule point of view.
The CAD geometry was split between the outer skin of the cockpit and the internal structure (frames/ stringers etc.) to further optimise mesh efforts. At a later stage the meshed parts were connected using rigid elements, a method which was verified to yield good results wrt to a merged approach (which was the baseline). The result of this verification were presented in a separate presentation.