Septum Cap Frictional Locking for Jet Engine Acoustic Honeycomb
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Solution Overview
Problem
Existing acoustic systems for noise attenuation in jet engines face challenges in incorporating thin and flexible acoustic materials into honeycomb structures without compromising strength or creating unnecessary adhesive issues, particularly in forming non-planar structures like nacelles.
Innovation Solution
The use of septum caps made from acoustic material sheets, with a flange portion providing a wide anchoring surface for frictional locking within honeycomb cells, allowing for secure bonding without seams and maintaining structural flexibility, and enabling fine-tuning of noise attenuation through multiple cap placements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thin acoustic materials are placed between two honeycomb slices and bonded, then acoustic impedance is created and bonding is simple, but the structure strength is limited by the bond and bonding surface area
Solution Approach 1:
The invention divides the bonding interface into two separate surfaces: the anchoring surface of the acoustic material and the inner surface of the honeycomb cell. This segmentation allows each surface to be optimized independently - the anchoring surface can be treated to enhance adhesion while the honeycomb inner surface provides structural support, thereby resolving the contradiction between bonding simplicity and structure strength.
Solution Approach 2:
The invention extends the bonding interaction from a single-plane contact to a multi-dimensional anchoring system. The acoustic material is positioned within the honeycomb cell cavity, creating bonding interactions in multiple directions (radial anchoring to cell walls), which transforms a limited surface-area bond into a volumetrically-supported strong connection.
2Ease of manufacture
If thin acoustic materials are placed between two honeycomb slices, then acoustic impedance is created, but the bonding surface area is limited to the edges of the honeycomb
Solution Approach 1:
The bonding surface is segmented into the anchoring surface of the acoustic material and the honeycomb cell wall surface. This segmentation allows the acoustic material to present a dedicated bonding interface (anchoring surface) that is optimized for adhesion, rather than relying on the limited edge surface of the honeycomb slice.
Solution Approach 2:
The acoustic material itself acts as an intermediary element that provides the bonding interface. By incorporating an anchoring surface on the acoustic material, the invention creates a dedicated bonding mediator between the acoustic functional layer and the honeycomb structure, significantly increasing the effective bonding surface area beyond what is available on the honeycomb edges alone.
3Reliability
If adhesive is applied during bonding, then permanent bond is achieved, but holes in acoustic material may be closed with excess adhesive
Solution Approach 1:
The acoustic material is designed with non-uniform local properties: the anchoring surface has high adhesion quality for bonding, while the resonator portion maintains hole openness for acoustic function. This local quality differentiation allows adhesive to be effectively applied at the anchoring surface without compromising the hole structure in the resonator portion, resolving the contradiction between bond permanence and hole openness.
Solution Approach 2:
The acoustic material is segmented into functionally distinct zones: an anchoring surface dedicated to bonding and a resonator portion dedicated to acoustic impedance. This segmentation isolates the adhesive application zone to the anchoring surface, preventing excess adhesive from reaching and blocking the holes in the resonator portion, thereby maintaining both bond reliability and acoustic functionality.
4Strength
If thick solid inserts are used in honeycomb cells, then structure strength is improved, but the honeycomb becomes stiff and difficult to form into non-planar structures
Solution Approach 1:
The invention uses thin acoustic material sheets with an anchoring surface instead of thick solid inserts. These thin films provide sufficient structural reinforcement when properly anchored to the honeycomb cell walls, while maintaining the flexibility needed to form the honeycomb into complex non-planar shapes like nacelles, thereby resolving the contradiction between strength and formability.
Solution Approach 2:
The invention transitions from using thick inserts (one-dimensional bulk elements) to thin acoustic materials with extended anchoring surfaces (two-dimensional interface elements). This dimensional change allows the acoustic material to achieve structural reinforcement through surface area rather than thickness, maintaining honeycomb flexibility for forming non-planar structures while providing adequate strength.
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 solution enhances noise attenuation efficiency, maintains structural integrity, and allows for flexible acoustic designs suitable for non-planar structures by providing a secure and adaptable acoustic impedance system.
Implementation Method 1
The septum caps are initially held in place within the cells by frictional locking between the anchoring surface and the cell walls
Implementation Method 2
An adhesive is applied to the anchoring surface of the septum caps to provide a permanent bond
Implementation Method 3
The closing of the cells with acoustic material creates the acoustic impedance upon which the resonator is based
Data Source
Figure 1~4
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Figure 8~9
AI summary
An acoustic structure that includes a honeycomb having cells in which septum caps are located. The septum caps are formed from sheets of acoustic material and include a resonator portion and a flange portion. An adhesive flow barrier is arranged along the outer edge of the resonator portion of the septum caps. The flange portion has an anchoring surface that provides frictional engagement of the septum caps to the honeycomb cells when the caps are inserted into the honeycomb during fabrication of the acoustic structure. An adhesive is applied to the anchoring surface of the septum caps after the caps have been inserted into the honeycomb cells to provide a permanent bond.