Double-Wall Panel With High Surface Area Core for Road Noise
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Solution Overview
Problem
Existing automotive panel structures fail to effectively increase road noise transmission loss due to limitations in the design of double-wall panels, particularly in the adaptation and modification of sound damping materials within the system, and do not adequately address the interaction between the damping material, inner wall, outer wall, and gas enclosed between them.
Innovation Solution
A double-wall panel configuration with a core material having a specific surface area of 20,000 mm2/cm3 or more, a packing density of 0.11 g/cm3 or less, and a stiffness ratio between the inner and outer walls that allows for enhanced sound damping, where the outer wall has lower stiffness than the inner wall, and the core material is formed of fibrous or gas-permeable foam substances with an open-cell structure, optimizing the heat absorption and energy conversion of sound waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the core material is designed with higher density to increase sound damping, then the sound insulation performance improves, but the weight of the panel increases
Solution Approach 1:
The core material is designed with a porous structure (foam or fibrous material with voids) having a packing density of 0.05-0.15 g/cm³. The porous structure provides large specific surface area for sound energy absorption while maintaining low density, thus achieving good sound insulation performance without increasing panel weight. The pores allow sound waves to penetrate and dissipate energy through friction and viscous effects.
Solution Approach 2:
The invention optimizes the packing density parameter of the core material to a specific range (0.05-0.15 g/cm³) rather than using high-density materials. This parameter change enables the core material to achieve effective sound damping through its porous structure while keeping the panel weight low, resolving the contradiction between sound insulation performance and weight.
2Reliability
If the core material packing density is increased to improve sound damping, then the transmission loss increases, but the specific surface area decreases
Solution Approach 1:
The core material utilizes a porous structure with optimized packing density (0.05-0.15 g/cm³) that maintains high specific surface area while providing sufficient sound damping. The porous network provides extensive surface area for sound wave interaction, enabling effective energy dissipation through viscous friction and thermal conduction without requiring high material density.
Solution Approach 2:
The invention employs composite core materials (foam or fibrous structures) that combine low-density matrix with high-surface-area internal structure. This composite approach allows the material to achieve both low packing density (for high specific surface area) and effective sound damping performance simultaneously, resolving the contradiction between transmission loss and specific surface area.
3Reliability
If the thickness of the double-wall panel is increased to improve sound insulation, then the transmission loss increases, but the panel thickness exceeds practical limits
Solution Approach 1:
The invention changes the approach from increasing panel thickness to optimizing the packing density parameter of the core material (0.05-0.15 g/cm³). This parameter optimization enables effective sound insulation within a practical thickness range by maximizing the sound damping efficiency per unit thickness through the porous core material structure.
Solution Approach 2:
The porous core material with optimized packing density provides enhanced sound damping per unit thickness compared to solid materials. The porous structure increases the interaction path length for sound waves within the panel thickness, improving sound insulation performance without requiring increased panel thickness.
4Ease of manufacture
If conventional damping materials are used without system optimization, then the manufacturing is simple, but the road noise transmission loss is insufficient
Solution Approach 1:
The invention specifies optimal parameter ranges for the core material (packing density: 0.05-0.15 g/cm³, specific surface area: 20,000 mm²/cm³ or more) that can be achieved through conventional manufacturing processes. These parameter specifications enable effective sound insulation without requiring complex manufacturing, resolving the contradiction between manufacturing simplicity and transmission loss performance.
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
Significantly increases road noise transmission loss while maintaining a practical thickness range, ensuring both sound and heat insulation properties without increasing the weight of the panel, and allows for efficient sound damping through the movement of gas in the core layer, enhancing the overall sound insulation performance.
Implementation Method 1
the heat absorption effect of the core material can reduce the spring elastic modulus k of the core layer and thereby reduce the resonant frequency of the double-wall panel
Implementation Method 2
the damping material as the core material is formed of a material in the shape of spherical grains or fibers, which are in contact with each other but are not fixed to each other, and therefore, can easily convert the energy of sound into kinetic energy
Data Source
AI summary
In order to increase road noise transmission loss, a double-wall panel includes a core material. The core material is enclosed between an outer wall and an inner wall facing each other, and has at least a predetermined thickness across the panel in all in-plane directions of the walls. The core material has a specific surface area of 20,000 (mm2/cm3) or more, where the specific surface area is defined as a surface area per unit volume.