Viscoelastic Interlayer Damping Windshield Frequencies
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Solution Overview
Problem
Standard plastic films in laminated glazing are not effective in improving acoustic comfort, particularly in damping the second and third natural frequencies of windshields, which are troublesome acoustically, and existing interlayers do not optimize vibro-acoustic damping without increasing the weight of the windshield.
Innovation Solution
A viscoelastic plastic interlayer with specific shear modulus and loss factor characteristics is selected, comprising two outer layers and a central layer, with the outer layers having a shear modulus greater than or equal to 3.10^7 Pa and a central layer thickness less than or equal to 0.3 mm, optimized to achieve enhanced vibro-acoustic damping without increasing the windshield's weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If standard plastic films are used in laminated glazing, then manufacturing simplicity is maintained, but acoustic comfort is not improved
Solution Approach 1:
The patent applies parameter changes by specifying precise rheological parameters for the viscoelastic plastic material: loss factor tan δ greater than 0.6 and shear modulus G' between 10^6 and 10^8 Pa. These parameter specifications transform the selection process from qualitative to quantitative, enabling manufacturers to select materials that simultaneously achieve acoustic damping performance and structural requirements without compromising manufacturing simplicity
Solution Approach 2:
The patent employs composite materials by defining an interlayer composed of viscoelastic plastic material with specific combinations of damping and structural properties. This composite approach allows the interlayer to function both as an acoustic dampener and as a structural component meeting regulatory standards, resolving the contradiction between acoustic performance and manufacturing ease
2Object-affected harmful factors
If existing interlayers with high loss factor are used, then acoustic damping is improved, but the windshield weight increases
Solution Approach 1:
The patent resolves the weight-damping contradiction through parameter changes by optimizing the shear modulus G' to be between 10^6 and 10^8 Pa and specifying thickness parameters. This quantitative approach enables selection of interlayer materials that provide sufficient acoustic damping while minimizing weight, directly addressing the contradiction between damping performance and weight
Solution Approach 2:
The patent applies local quality by differentiating the properties of the central layer versus outer layers. The central layer is optimized for acoustic damping with specific loss factor and shear modulus characteristics, while outer layers are optimized for structural integrity and adhesion. This localized optimization allows each layer to perform its specific function efficiently without unnecessary weight
3Object-affected harmful factors
If the interlayer thickness is increased to improve damping, then acoustic comfort improves, but the windshield becomes heavier and less maneuverable
Solution Approach 1:
The patent uses parameter changes to resolve the thickness-maneuverability contradiction by specifying optimal thickness ranges and the relationship G'/h between shear modulus and thickness. This quantitative specification enables achieving acoustic damping performance with minimized thickness, thereby maintaining maneuverability while improving acoustic comfort
Solution Approach 2:
The patent applies local quality by concentrating the acoustic damping function in the central layer with optimized thickness and material properties, while outer layers provide structural support. This functional differentiation allows the damping-critical central layer to be thin and efficient, while outer layers compensate for structural requirements, resolving the contradiction between damping thickness and maneuverability
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 interlayer effectively optimizes the damping of the first natural frequencies, particularly the second and third frequencies, of windshields, improving acoustic comfort without adding weight, thereby enhancing the maneuverability and reducing fuel consumption of vehicles.
Implementation Method 1
a first element 3 of viscoelastic plastic material intended to constitute the central layer and a second element of viscoelastic plastic material intended to constitute the external layers are provided
Implementation Method 2
The loss factor tan δ of the material constituting the interlayer film... characterizes the ability of the material to dissipate energy
Data Source
Figure 1
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Figure 4~5
AI summary
The invention relates to a method for selecting a viscoelastic plastic separator, including two outer layers and a central layer, and which is adapted to be inserted between two glass sheets of a glass panel, wherein the method includes the following steps: providing first and second elements for respectively forming the central layer and the outer layers; measuring the shear modulus G' of the first and second elements; selecting the material of the second element only if G' = 3.107 Pa at 20°C and between 100 Hz and 240 Hz; setting the thickness h of the first element such that h = 0.3 mm and such that g=G'/h is between 8.108 Pa/m and 2.67.109 Pa/m at 20°C and between 100 Hz and 240 Hz. The invention can be used for optimizing the damping of the second and third frequencies particular to a vehicle windshield without making the windshield heavier.