Acoustic Panel Inserts for Sub-Millimeter Holes
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Solution Overview
Problem
Existing acoustic panels in aircraft nacelles struggle to effectively absorb low-frequency noise due to limitations in drilling small diameters, which can damage composite fibers and restrict hole size to 1 mm.
Innovation Solution
A production method involving inserts with hollow cylinders and cone-shaped caps allows for the creation of acoustic panels with holes less than 1 mm in diameter, ensuring better low-frequency noise attenuation by positioning and polymerizing these inserts within a composite structure before fixing a honeycomb and rear skin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If drilling tools are used to create holes in the composite structure, then holes can be created for acoustic wave passage, but the hole diameter is limited to 1 mm and composite fibers may be severed
Solution Approach 1:
The inserts with through-bores are positioned in the composite structure before polymerization, allowing the holes to be formed during the molding process rather than by subsequent drilling. This preliminary formation of holes avoids the need for post-polymerization drilling that would sever composite fibers.
Solution Approach 2:
The inserts act as intermediary elements that provide the through-bores during the composite structure formation. The inserts are temporarily embedded in the composite structure, allowing hole formation without direct drilling of the final polymerized material, thus protecting fiber integrity.
2Reliability
If hole diameter is reduced to absorb low-frequency noise, then acoustic absorption improves, but manufacturing difficulty increases due to drilling limitations
Solution Approach 1:
The mechanical drilling process is replaced by a molding process where inserts with pre-formed through-bores are positioned in the composite structure before polymerization. This substitution allows creation of small diameter holes (less than 1 mm) that are impossible to achieve with drilling tools, while simultaneously improving acoustic absorption of low-frequency noise.
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 method enables the production of acoustic panels with very small diameter holes, enhancing the attenuation of low-frequency acoustic waves and preventing damage to composite fibers during the process.
Implementation Method 1
a polymerization step during which the composite structure with the inserts is polymerized
Data Source
AI summary
A production method for an acoustic panel comprising a step of producing a composite structure, a step of providing inserts, wherein each insert comprises a nozzle formed as a hollow cylinder with a through-bore and a cap comprising a base formed as a cylinder and a cover formed as a cone, and wherein the base is accommodated in the bore, a step of positioning the inserts in the composite structure by penetration of the cover into the composite structure so that the bore opens at one side and the other of the composite structure, a step of polymerizing during which the composite structure with the inserts is polymerized, a step of removing the caps, a first step of fixing a honeycomb structure to the polymerized composite structure, and a second step of fixing a rear skin to the honeycomb structure.