Gas Permeable Composite Facesheet for Acoustic Attenuation

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Solution Overview

Problem

Conventional acoustic attenuation structures with perforated composite sheets face challenges such as increased manufacturing time, aerodynamic drag, and the need for multiple curing stages, which affect efficiency and performance.

Innovation Solution

A method and system that form a gas permeable composite facesheet by heating air flowing through a composite material, eliminating perforations and reducing manufacturing steps, using a pressure chamber and vacuum bag setup to control porosity and permeability without additional adhesives.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a perforated composite sheet is used in conventional acoustic attenuation structures, then sound attenuation is achieved, but manufacturing time increases and aerodynamic drag increases

Engineering Contradiction:

Improvesound attenuationVSAvoidmanufacturing time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent uses a porous Teflon membrane instead of a perforated composite sheet. The membrane inherently provides sound attenuation through its porous structure while eliminating the need for perforation operations, thereby reducing manufacturing time and steps.

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The patent employs a composite structure consisting of a porous Teflon membrane combined with acoustic foam material. This composite approach achieves effective sound attenuation while maintaining a streamlined surface that reduces aerodynamic drag compared to traditional perforated composite sheets.

Inventive Principle:

Principle #40Composite materials

2Reliability

If a perforated composite sheet is used in conventional acoustic attenuation structures, then sound attenuation is achieved, but aerodynamic drag increases

Engineering Contradiction:

Improvesound attenuationVSAvoidaerodynamic drag

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The porous Teflon membrane provides sound attenuation functionality while maintaining a smooth external surface. The porosity is internal to the membrane structure, allowing sound waves to pass through without creating surface irregularities that would increase aerodynamic drag.

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The thin Teflon membrane acts as a flexible barrier that can be tightly integrated with the underlying acoustic foam. This creates a smooth, continuous surface profile that minimizes aerodynamic interference while the membrane's porous structure enables sound attenuation.

Inventive Principle:

Principle #30Flexible shells and thin films

3Strength

If multiple curing stages are used in conventional acoustic attenuation structures, then structural integrity is achieved, but manufacturing time increases

Engineering Contradiction:

Improvestructural integrityVSAvoidmanufacturing time

Core Design Contradiction:

StrengthVSLoss of time

Solution Approach 1:

The patent extracts the Teflon membrane as a separate, pre-formed component that requires no curing process. By removing the membrane formation step from the curing sequence, the structure achieves structural integrity through fewer curing stages, reducing manufacturing time while maintaining strength.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The Teflon membrane is prepared and assembled into the acoustic attenuation structure before the curing of the acoustic foam occurs. This preliminary assembly allows the membrane to be positioned and secured without requiring subsequent curing operations, streamlining the manufacturing process.

Inventive Principle:

Principle #10Preliminary action

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

This approach reduces manufacturing time, minimizes aerodynamic drag, and enhances acoustic attenuation performance by creating a smooth, permeable surface with controlled porosity, suitable for various applications including aircraft noise reduction.

Implementation Method 1

The composite material is heated while flowing air through its thickness to form a gas permeable composite facesheet

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 2

the composite material acts as a rate limiting structure for movement of air between a first pressure within the pressure chamber and a second pressure within the pressure chamber

Methodology Applied

Scientific EffectPressure gradient driven flow: Pressure Gradient

Implementation Method 3

The vacuum bag is sealed to the tooling base. A second pressure is supplied through the vacuum bag. The first pressure and the second pressure are lower than a pressure outside of the vacuum bag.

Methodology Applied

Scientific EffectVacuum pressure: Vacuum

Data Source

PatentUS10927543B2Acoustic attenuation structure

Publication Date: 2021.02.23 THE BOEING CO

AI summary

An acoustic attenuation structure comprises a gas permeable composite facesheet, a cellular core, and an impermeable backing. The gas permeable composite facesheet has a designated porosity. The designated porosity causes the permeability of the gas permeable composite facesheet. The gas permeable composite facesheet comprises a carbon fiber fabric. The cellular core is bonded to the gas permeable composite facesheet using a resin of the gas permeable composite facesheet without any additional adhesive. The impermeable backing is connected to the cellular core.