Hybrid Resistive Skin Shell for Aircraft Air Intake
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Solution Overview
Problem
Existing resistive skin shells for aircraft air intakes face challenges in maintaining acoustic performance over time due to material erosion and increased open surface ratio, leading to degraded sound damping and structural integrity under mechanical stresses.
Innovation Solution
A hybrid resistive skin shell composed of perforated metal bands with composite solid bands, where the perforations are located only in the metal bands, reducing erosion and providing mechanical strength, and the composite solid bands contribute to structural integrity while maintaining a smooth outer surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistive skin shells are made of composite material with drilled orifices, then acoustic waves can pass through, but the material erodes over time increasing open surface ratio and degrading acoustic performance
Solution Approach 1:
The patent uses a composite structure combining metal bands with perforations and composite solid bands. The metal bands provide erosion-resistant perforations that maintain acoustic performance, while the composite material provides structural integrity. This composite approach resolves the contradiction by combining the erosion resistance of metal with the acoustic permeability of perforated structures.
Solution Approach 2:
The patent changes the material parameter from pure composite to a hybrid metal-composite structure. The metal bands have different erosion characteristics compared to pure composite material, allowing the open surface ratio to remain stable over time while maintaining acoustic wave passage capability.
2Reliability
If perforations are drilled in composite shells, then sound waves can pass through, but mechanical strength is reduced under aerodynamic stresses
Solution Approach 1:
The patent creates a composite structure where metal bands with perforations are combined with composite solid bands. The metal bands handle acoustic wave transmission through their controlled perforations, while the composite bands provide structural strength and stiffness to withstand aerodynamic loads, resolving the strength-permeability trade-off.
Solution Approach 2:
The resistive skin shell is segmented into alternating metal bands and composite solid bands. This segmentation allows different parts of the structure to perform different functions: metal bands for acoustic transmission and composite bands for structural support, optimizing both acoustic performance and mechanical strength.
3Loss of energy
If open surface ratio is increased to improve acoustic damping, then sound energy dissipation improves, but structural integrity and resistance to mechanical stresses deteriorate
Solution Approach 1:
The patent uses a composite structure where metal bands with controlled perforations provide acoustic damping through sound energy dissipation, while composite solid bands maintain structural integrity. The combination allows optimal open surface ratio for acoustic damping without compromising mechanical strength under aerodynamic stresses.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The hybrid design ensures future-proof acoustic performance with reduced drag and minimized risk of perforation blockage, while offering enhanced mechanical strength to withstand mechanical stresses, thus maintaining acoustic specifications throughout the lifespan of the aircraft nacelle.
Implementation Method 1
perforated metal bands which extend in a longitudinal direction and are spaced apart from one another in a transverse direction
Implementation Method 2
a cellular damping core, generally in honeycomb form, on either side of which the resistive skin and the rear skin are fixed, which core contributes both to the mechanical strength and to the acoustic damping, the main function of the core being to capture and dampen the sound waves
Implementation Method 3
the aim of this resistive skin is to allow the passage of the sound waves and possibly also at least partially dissipate the energy thereof in thermal form
Data Source
AI summary
A resistive skin shell for an acoustic panel or inner wall of an aircraft air intake, comprising an alternation, in a transverse direction, of perforated metal bands and of composite solid bands extending in a longitudinal direction. The perforated metal bands and the composite solid bands form a smooth outer face configured to be in contact with an aerodynamic stream, and a crenelated inner face. The composite solid bands have a thickness greater than the perforated metal bands. Since the perforations are provided in metal bands, which are intrinsically resistant to wear and erosion, the future proofing of the acoustic performance of the resistive skin is guaranteed. Since the composite solid bands, which are thicker, can ensure the mechanical strength of the skin, the thickness of the perforated metal bands can be reduced, allowing perforations with dimensions that are also reduced, having a lower impact on drag.