Final Report Summary - DYNAPIT (Nose Fuselage/Cockpit Dynamic Characterization for Internal Noise Attenuation) Executive Summary: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.Project Context and Objectives:The main objective of DynaPit project was detailed simulation of the low frequency structural dynamics and cockpit acoustic performance of Carbon Fibre Reinforced Polymer (CFRP) nose fuselage design, with a comparative analysis of a conventional metallic design.The low weight of CFRP is desirable for reducing fuel consumption, a key objective of the Green Regional Transport demonstrator. Furthermore, the use of CFRP materials in fuselage structures has a number of benefits including a more comfortable cabin pressure due to the higher strength and higher permissible cabin humidity since composites are not subject to corrosion. The additional strength of composites also allows for bigger windows, improving the visibility for crew and passengers.Although a CFRP fuselage would offer many benefits with respect to the traditional metallic materials, it has not yet been implemented in medium or large passenger aircraft in Europe. An important issue that still needs to be assessed is the effect of the CFRP structure on the acoustic environment inside the cockpit.The physical characteristics of the CFRP structural components give a different vibroacoustic response compared to metallic structures. CFRP structures generally have relatively low damping of the order of 0.5% compared with around 2% for metallic structures. This, combined with the reduced number of mechanical joints that is made possible by CFRP technologies, might lead to higher noise levels in the cockpit.The novelty of the project was in the application of FEM/FEM and FEM/BEM analysis techniques to accurately assess the structural dynamics and resulting internal acoustics of a new nose fuselage and cockpit design purely by computational analysis. Only in recent years has the accuracy of vibroacoustic analysis methods reached a level suitable to support the design phase, and this has been proven in other domains of engineering, most notably in the automotive industry where it is now commonplace to model the automobile’s internal acoustic environment as part of the design process. Comparatively, there has been little application of such techniques to aircraft acoustic assessments of this type.Project Results:not applicablePotential Impact:not applicableList of Websites:not applicable
