Cork-Based Electromagnetic Wave Absorbing Composite Material
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Solution Overview
Problem
Current electromagnetic wave absorbers, such as pyramidal absorbers made of polyurethane foam filled with carbon black, suffer from manufacturing inhomogeneity and complex machining due to weak mechanical properties, leading to non-reproducibility of dimensions and properties, especially in complex shapes like pyramids.
Innovation Solution
A composite material using cork as the supporting matrix with particles of 10 μm to 5 mm diameter and a filler that absorbs electromagnetic waves, providing improved mechanical strength, reproducibility, and environmental sustainability, along with a method involving coating cork particles with a filler and using a binder to achieve desired shapes and properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyurethane foam is used as the supporting matrix for electromagnetic wave absorption, then the material achieves good electromagnetic absorption performance, but the manufacturing process becomes complicated and produces inhomogeneous composition
Solution Approach 1:
The patent uses a composite material consisting of cork particles (natural or expanded) combined with carbon-based filler (carbon black, graphite, or carbon fibers) embedded in a polymer matrix. This composite structure provides both the mechanical support needed for complex shapes and the electromagnetic absorption properties, while the cork's natural porosity allows uniform filler distribution, resolving the contradiction between performance and manufacturing precision.
Solution Approach 2:
The patent exploits the porous structure of cork particles (with porosity between 60-80%) to facilitate uniform impregnation with carbon-based filler solutions. The pores act as natural channels for filler penetration, ensuring homogeneous composition throughout the material, especially in complex pyramidal geometries, thereby improving manufacturing precision without compromising electromagnetic absorption performance.
2Reliability
If polyurethane foam is used as the supporting matrix, then electromagnetic absorption is achieved, but machining becomes complicated due to weak mechanical properties
Solution Approach 1:
The cork-based composite material combines the mechanical strength of cork (with compressive strength 2-4 times higher than PU foam) and polymer matrix with the electromagnetic absorption properties of carbon filler. This composite structure maintains good electromagnetic absorption performance while significantly improving mechanical properties, making machining and manufacturing of complex shapes much easier and more precise.
Solution Approach 2:
The patent changes the mechanical parameters of the supporting matrix by replacing soft PU foam with harder cork material having superior mechanical properties (compressive strength 0.2-0.4 MPa for cork vs. 0.05-0.1 MPa for PU foam). This parameter change enables easier machining and manufacturing while maintaining the required electromagnetic absorption performance through optimized filler content and distribution.
3Ease of manufacture
If polyurethane foam is used, then the material can be manufactured with filler impregnation, but the final product dimensions and properties are non-reproducible
Solution Approach 1:
The cork particles provide a stable, reproducible porous structure with consistent porosity (60-80%) and particle size distribution (1-5 mm). This uniform porous framework ensures that filler impregnation produces consistent results across different batches, while the rigid cork structure maintains dimensional stability during manufacturing, achieving both ease of manufacture and dimensional reproducibility.
Solution Approach 2:
The patent achieves homogeneous distribution of carbon filler throughout the cork-based matrix through the cork's uniform porous structure. The consistent pore size and distribution in cork particles ensure uniform filler impregnation, leading to reproducible electromagnetic absorption properties and dimensions across different production batches, unlike the inhomogeneous PU foam structure.
4Reliability
If conventional PU foam absorbers are used, then electromagnetic absorption is achieved, but the material has negative environmental impact due to petrochemical origin
Solution Approach 1:
The patent creates a composite material combining natural cork (a renewable, biodegradable resource) with carbon-based filler and polymer binder. This composite provides equivalent electromagnetic absorption performance to conventional PU foam absorbers while significantly reducing environmental impact through the use of sustainable cork material, eliminating the need for petrochemical-based foams.
Solution Approach 2:
The patent promotes the use of natural cork, a renewable resource that can be sustainably harvested, replacing finite petrochemical resources. Cork is biodegradable and has low environmental impact throughout its lifecycle, making it an eco-friendly alternative to conventional PU foam that aligns with green manufacturing and sustainability goals while maintaining electromagnetic absorption 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
The cork-based composite material achieves identical or better performance in electromagnetic wave absorption with improved reproducibility and environmental benefits, suitable for anechoic chambers and stealth devices, while adhering to fire safety and environmental norms.
Implementation Method 1
said composite material has a real permittivity greater than 1.2 and a dielectric loss tangent tan δ greater than 0.1
Implementation Method 2
a filler that absorbs electromagnetic waves
Data Source
AI summary
One subject of the present invention is an electromagnetic-wave-absorbing composite material comprising a carrier matrix (11) and an electromagnetic-wave-absorbing filler (12). According to the invention, the carrier matrix (11) is a cork matrix, which is formed of particles the equivalent diameter Del of which is comprised between 10 μm and 5 mm, and the composite material (1) has a real permittivity higher than 1.2 and a dielectric loss tangent tan δ higher than 0.1. Another subject of the present invention is a method for producing such a material, and the use of this material as an absorber, in particular in an anechoic chamber, or as a radar absorber in stealth devices, or even to improve the electromagnetic compatibility of electronic devices.