To tackle with noise issue specific structures are applied in aircrafts design. These structures reduce noise through its absorption and prevent it from entering the cabin by using sound insulation. Apart from solving acoustic issues, acoustic structures have to perform other functions as well, such as load bearing, airtightness, vibration resistance and heat resistance.
Basic requirement for any aircraft structure is weight efficacy. That is why in order to solve acoustic issues in aircrafts, the list of approved materials is significantly reduced, as either they don’t have versatility or are not acceptable by weight efficacy criterion.
Folded core has sufficient sound absorption even without using Helmholtz resonant chambers; it has large absorption compared to usual linear crimp and has a wider range of efficient sound-absorption compared to the structures having resonant-type absorption.
Sandwich panels with folded core provide good sound insulation due to the following properties:
- Wide-band sound-absorption due to resonant effect in the chambers, formed by the channels of Z-crimp with alternating height.
- Combination of a few layers of the core from different materials and with different height. It is also possible to design a multilayer structure without increase of the height of the panel (‘Matryoshka’-type structure).
- Loss of sound wave energy due to friction when the air travels through the material of a folded core and lamellar crimp, using hybrid materials with different acoustic resistance.
- Increase of sound-absorption due to ‘maze’ effect – friction inside the channels.
|Application of Z-crimp folded core for cound insulation of ПС-90 engine nacelle||A part of multi-tier sound-absorbing panel with Z-crimp folded core|
|Multilayer structure||Multilayer structure|