Magnetic Coupling for Interply Conductivity Assessment
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Solution Overview
Problem
Conventional methods for measuring interply conductivity in composite materials like carbon fiber reinforced plastic (CFRP) are time-consuming, laborious, and invasive, often causing degradation and requiring direct contact, which complicates lightning protection and induction heating applications.
Innovation Solution
A non-destructive testing system using a pair of coils to measure the shielding effectiveness of a CFRP panel over a broad frequency range, calculating effective conductivity through finite element analysis, allowing for non-contact testing and accounting for anisotropic conductivity in composite materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current pulse measurements with direct electrical contact are used to measure interply conductivity, then measurement precision can be achieved, but the testing process becomes time-consuming and laborious requiring machining, sanding and plating
Solution Approach 1:
The patent replaces direct electrical contact measurement methods with electromagnetic induction using coils. The system uses a transmit coil to generate an alternating magnetic field that induces eddy currents in the conductive composite, and a receive coil to detect the magnetic field. This substitution of mechanical/electrical contact with electromagnetic field interaction eliminates the need for machining, sanding, and plating while maintaining measurement capability.
Solution Approach 2:
The patent introduces magnetic coupling as an intermediary mechanism between the measurement system and the conductive composite. The coils are positioned at a distance from the specimen, using magnetic field coupling to transfer energy and information without direct contact. This intermediary approach allows non-contact measurement while still achieving precise conductivity assessment.
2Measurement precision
If direct contact measurement methods are used, then conductivity can be measured, but the specimen undergoes degradation and cannot be used again
Solution Approach 1:
The patent replaces direct physical contact with electromagnetic field interaction. The coils generate and detect magnetic fields that penetrate the conductive composite without requiring physical contact or modification of the specimen surface. This eliminates degradation from machining, sanding, and plating while preserving specimen integrity for reuse.
Solution Approach 2:
The patent creates a magnetic field copy or representation of the electrical conductivity characteristics. Instead of physically contacting and potentially damaging the specimen, the electromagnetic fields interact with the conductive composite to produce measurable signals that represent the conductivity properties, allowing non-destructive assessment.
3Measurement precision
If conventional measurement techniques are used on composite materials, then conductivity data can be obtained, but the process is complex and requires special preparation of specimens
Solution Approach 1:
The patent creates a universal measurement system using electromagnetic coils that can measure interply conductivity without requiring specimen-specific preparation. The same coil-based apparatus can be applied to various conductive composite specimens regardless of their geometry or surface characteristics, eliminating the need for specialized machining, sanding, or plating procedures for each test.
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
This method provides efficient and non-destructive characterization of interply conductivity, reducing testing time and avoiding material degradation, thereby improving lightning protection and induction heating processes.
Implementation Method 1
A transmit coil is driven with an alternating current over a broad frequency range to generate an alternating magnetic field
Implementation Method 2
The alternating magnetic field generates eddy currents within the conductive composite material structure
Implementation Method 3
The eddy currents generate heat within the conductive composite material structure
Implementation Method 4
A receive coil is magnetically coupled to the transmit coil and the conductive composite material structure
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A method is provided that includes setting up a composite material structure under test (SUT) between a transmit coil and a receive coil. The transmit coil is driven with a RF signal over a plurality of frequencies, thereby causing the transmit coil to produce a magnetic field that by magnetic coupling through the SUT induces a voltage in the receive coil. The voltage in the receive coil is measured, and from the voltage, a measurement of attenuation of the RF signal caused by the SUT between the transmit coil and receive coil is produced. And an effective conductivity of the SUT is calculated from the measurement of attenuation.