Needled Fibrous Trim Structure for Mid-Low Frequency Sound Absorption
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Solution Overview
Problem
Existing automotive sound-absorbing trim components have limited performance in mid-low frequencies due to thickness constraints, leading to increased production complexity, material waste, and difficulty in controlling Air Flow Resistance (AFR) when using additional patches or resistive porous screens.
Innovation Solution
A sound-absorbing trim component comprising a porous fibrous resistive layer with higher AFR than the carrier layer, formed by depositing loose fibers on a substrate layer and consolidating through needling, followed by thermoforming, allowing localized control of AFR and simplified production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional sound-absorbing patches are applied to increase mid-low frequency absorption, then sound-absorption performance is improved, but production complexity increases and material waste increases
Solution Approach 1:
The patent merges the sound-absorbing function directly into the base trim component by forming a porous fibrous layer during the thermoforming process itself, rather than applying separate patches. This integration eliminates additional production steps and material waste while maintaining sound-absorption performance in the mid-low frequency range (100-2000 Hz).
Solution Approach 2:
The patent uses a porous fibrous layer formed from loose fibers during thermoforming to provide sound-absorbing capabilities. The porous structure allows acoustic waves to penetrate and dissipate energy through viscous and thermal mechanisms, effectively improving mid-low frequency absorption without requiring additional patches.
2Reliability
If additional sound-absorbing patches are applied to increase mid-low frequency absorption, then sound-absorption performance is improved, but packaging space requirements increase
Solution Approach 1:
The sound-absorbing porous fibrous layer is integrated into the base trim component during manufacturing, eliminating the need for separate patches that would require additional packaging space. The combined structure maintains all sound-absorption functions within the original component volume.
3Reliability
If resistive porous screens are used to control Air Flow Resistance, then sound-absorption performance is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent controls the Air Flow Resistance (AFR) parameter by adjusting the composition and density of the loose fibers during the thermoforming process. By varying fiber type, fiber length, and deposition density, the AFR can be optimized for specific frequency ranges without requiring high-precision manufacturing tolerances, as the porous structure naturally provides the required resistance characteristics.
4Reliability
If component thickness is increased to improve sound-absorption performance, then mid-low frequency absorption is improved, but structural rigidity decreases
Solution Approach 1:
The patent incorporates a porous fibrous layer within the existing thickness constraints of the trim component. The porous structure provides sound-absorption functionality without significantly increasing overall thickness, and the fibrous nature of the material maintains structural rigidity while enabling acoustic energy dissipation through viscous and thermal mechanisms.
Solution Approach 2:
The patent creates a composite structure by combining the base trim component material with a porous fibrous layer formed during thermoforming. This composite approach allows the component to maintain the structural rigidity of the base material while adding sound-absorption capabilities through the porous fibrous layer, effectively addressing both mechanical and acoustic requirements within thickness constraints.
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 solution achieves excellent sound-absorption performance in mid-low frequencies without additional process steps or material waste, with adjustable AFR and simplified production, enhancing sound-insulation in automotive components.
Implementation Method 1
sound-absorbing trim components are those placed outside of the passenger compartment. These components can absorb the energy of the acoustic waves that are radiated by the vehicle's sound sources
Implementation Method 2
dissipate their energy, for example by viscous and/or thermal and/or structural dissipation mechanisms
Implementation Method 3
dissipate their energy, for example by viscous and/or thermal and/or structural dissipation mechanisms
Implementation Method 4
consolidate by needling the assembly consisting of the first and of the second porous fibrous layer
Implementation Method 5
thermoform the so consolidated assembly consisting of the first and of the second porous fibrous layer
Data Source
Figure 1~2
AI summary
A sound-absorbing trim component comprising a porous fibrous resistive layer and a porous fibrous carrier layer laminated together wherein the Air Flow Resistance of the porous fibrous resistive layer is higher than the Air Flow Resistance of the porous fibrous carrier layer and the sound-absorbing trim component is obtained by a process comprising the following steps: depositing on an area of a first porous fibrous layer a second porous fibrous layer consisting of loose fibers, consolidate by needling the assembly consisting of the first and of the second porous fibrous layers and eventually thermoform the consolidated assembly so that, after the thermoforming process, the first porous fibrous layer forms the porous fibrous carrier layer and the second porous fibrous layer forms the porous fibrous resistive layer.