Multilayer Molded Parts for Low-Reflection Microwave Attenuation
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Solution Overview
Problem
Conventional radar absorbing materials (RAM) either favor absorption or reflection, failing to achieve a balance between low reflectivity and high absorption, which is necessary for effective radar signal attenuation and sensor accuracy, particularly in molded parts thicker than 3 millimeters.
Innovation Solution
A multilayer part comprising a first layer with high dielectric constant and dissipation factor, combined with a second layer having low dielectric constant, optimized in thickness and filler content to achieve less than 15% reflectivity and less than 6% transmission, using specific polymer compositions and conductive carbon-based fillers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If higher conductivity carbon-based fillers are used to improve electromagnetic wave attenuation and reduce transmission, then absorption performance is improved, but reflection increases
Solution Approach 1:
The patent divides the single-layer RAM into multiple layers with different carbon filler conductivities. The first layer (higher conductivity, 3-15 wt%) handles absorption, while the second layer (lower conductivity, 1-5 wt%) reduces reflection. This segmentation resolves the contradiction by assigning different functions to different layers, achieving both high attenuation and low reflection simultaneously.
Solution Approach 2:
The patent applies local quality by giving each layer different carbon filler concentrations and conductivity properties tailored to its specific function. The first layer has higher conductivity optimized for absorption, while the second layer has lower conductivity optimized for reducing reflection. This localized optimization resolves the contradiction by matching material properties to functional requirements at each interface.
2Loss of energy
If conventional single-layer RAM is used to achieve absorption, then transmission is reduced, but reflection remains high and sensor accuracy decreases
Solution Approach 1:
The patent segments the RAM into two layers where the first layer (higher conductivity) provides strong absorption to reduce transmission, while the second layer (lower conductivity) minimizes reflection to improve sensor accuracy. This segmentation allows simultaneous optimization of both absorption and reflection properties that cannot be achieved in a single layer.
Solution Approach 2:
The patent uses composite material structure combining two different polymer-carbon compositions with distinct conductivity characteristics. This composite approach enables the system to exhibit both high absorption (from the first layer) and low reflection (from the second layer), resolving the contradiction between signal attenuation and sensor accuracy.
3Loss of energy
If molded parts are made thicker than 3 millimeters to improve absorption, then transmission is reduced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent segments the thick RAM into two functional layers with different thicknesses (first layer: 1-5 mm, second layer: 0.5-2 mm). This segmentation achieves effective absorption and low reflection in a optimized total thickness configuration, potentially reducing the required overall thickness compared to conventional single-layer designs while maintaining performance.
Solution Approach 2:
The patent changes the conductivity parameter distribution across layers rather than using uniform high conductivity throughout. The first layer uses higher conductivity (3-15 wt% carbon) for absorption, while the second layer uses lower conductivity (1-5 wt% carbon) to reduce reflection. This parameter optimization achieves effective attenuation at optimized thickness, reducing device complexity.
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 multilayer design achieves improved microwave absorption and reduced reflection, enhancing sensor accuracy by effectively attenuating radar signals in thinner molded parts.
Implementation Method 1
Absorption occurs when the electromagnetic field/photons interact and transfer energy to the substance/material they are striking instead of transmitting through or reflecting it
Implementation Method 2
For carbon-based compounds, a well percolated carbon network providing high electrical conductivity may provide good shielding performance. Moreover, the higher the conductivity the better the attenuation of electro-magnetic waves
Implementation Method 3
for reflection, the opposite occurs at lower conductivities leading to lower reflection of the radar waves
Data Source
Figure 1
Figure 2A~2B
Figure 3A
AI summary
Disclosed herein is a multilayer part comprising: a first layer, wherein the first layer comprises a first polymer composition comprising a first polymer and from about 0.1 wt. % to about 30 wt. % of a first electrically conductive carbon-based filler; a second layer disposed adjacent a surface of the first layer, wherein the second layer comprises a second polymer composition comprising a second polymer and from about 0.01 wt. % to about 10 wt. % of a second electrically conductive carbon-based filler; wherein the multilayer part exhibits a percent reflected power measured in transmission mode of less than 15% when observed according to a Free Space method at frequencies of from about 75 GHz to 110 GHz, when the multilayer part is oriented such that microwave radiation is incident to the second layer of the multilayer part.