Woven Laminate Acoustic Lining for Aircraft APU Sound Absorption
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Solution Overview
Problem
Existing sound absorption materials for auxiliary gas turbines in aircraft, such as sintered metal fibre fleeces, face challenges including high weight, complex processing, long sintering times, high costs, and brittle behavior due to strong oxide-forming alloying additions, which limit their effectiveness and efficiency.
Innovation Solution
A woven laminate composed of three superimposed and partially welded woven layers with different structures - fine, medium, and coarse - made of metallic wires, which provides excellent acoustic damping, deformation properties, and high corrosion resistance, allowing for flexible adaptation to various shapes and bending radii, and can be manufactured using resistance welding with profiled electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sintered metal fibre fleeces are used for sound absorption in high temperature environments, then acoustic absorption performance is achieved, but weight increases and processing complexity increases
Solution Approach 1:
The patent changes the material parameters by using metallic woven fabrics instead of sintered metal fibre fleeces, and changes the structural parameters by using multi-layer woven laminates with different mesh densities. This achieves acoustic absorption in high temperature environments while reducing weight and processing complexity compared to traditional sintered materials.
Solution Approach 2:
The patent employs composite materials by combining multiple woven layers with different mesh densities and metallic properties to create a woven laminate that achieves both acoustic absorption performance and reduced weight. The composite structure allows optimization of individual layer properties for specific acoustic frequency ranges.
2Reliability
If sintered metal fibre fleeces are used for sound absorption, then acoustic damping is achieved, but manufacturing time increases and cost increases
Solution Approach 1:
The patent replaces the thermal-sintering process with a mechanical weaving process. Instead of sintering metal fibres to create acoustic damping, the invention uses mechanically woven metallic fabrics with controlled mesh structures that provide acoustic damping through their physical configuration, thereby eliminating long sintering times and reducing manufacturing costs.
3Reliability
If sintered metal fibre fleeces are used for sound absorption, then acoustic absorption is achieved, but material brittleness increases
Solution Approach 1:
The patent changes the material state from sintered (brittle) to woven (ductile). By using metallic woven fabrics instead of sintered metal fibres, the material maintains acoustic absorption properties while gaining ductility and formability, as the woven structure allows plastic deformation without cracking.
4Reliability
If woven laminates with different mesh densities are used, then acoustic absorption across multiple frequencies is improved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the acoustic absorption function across multiple woven layers, where each layer with different mesh density targets specific frequency ranges. The coarse mesh layer handles lower frequencies while finer mesh layers handle higher frequencies, dividing the overall acoustic absorption task into manageable segments that can be manufactured separately and then assembled.
Solution Approach 2:
The patent adds the dimension of layer stacking to the woven structure. Instead of using a single woven layer with varying mesh densities, the invention stacks multiple woven layers with different mesh densities to create a laminate structure, thereby achieving broad-frequency acoustic absorption while maintaining manageable manufacturing complexity through modular assembly.
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 woven laminate achieves superior acoustic absorption properties, with up to 80% absorption in the 800-4000 Hz range, surpassing traditional metal fibre fleeces, and offers improved deformability and thermal welding behavior, making it suitable for high-temperature applications like aircraft APU sound absorbers.
Implementation Method 1
The functioning of the microporous materials is to convert the energy of sound pressure waves into thermal energy. For this, it is necessary to cause a certain pressure loss by means of the microporous material.
Implementation Method 2
The woven layers are welded together at least partially.
Data Source
AI summary
A woven laminate for sound absorption that includes a first woven layer, a second woven layer, and a third woven layer. The first woven layer has a coarse structure. The second woven layer has a fine structure. The third woven layer has a medium structure. Each of the first, second, and third woven layers are composed of metallic wires that are woven to each other or interlaced as a fleece. At least one of the first, the second, and the third woven layers are superimposed in order to form the woven laminate. The woven layers are placed in the layer order fine-coarse-medium. The woven layers are welded together at least partially.