Induction Heating for Polymer Composite Repair
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Solution Overview
Problem
Current repair methods for carbon fibre composites in aerospace applications face challenges such as inefficient heat transfer, damage to the parent structure, and the need for disassembly due to the use of thermal blankets or autoclaves, and the introduction of conductive additives which alter material properties and require additional testing.
Innovation Solution
A method using alternating current coils to induce eddy currents for heating the repair patch without metallic additives, determining optimal amp-turns and frequency based on desired temperature and penetration depth to ensure uniform curing without altering the composite's properties, allowing on-site and in-situ repairs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a thermal blanket is used to cure the patch, then the curing process can be performed on-site, but heat transfer efficiency is poor and temperature distribution through the patch thickness is non-uniform
Solution Approach 1:
The patent replaces the thermal blanket heating method with induction heating technology. The induction heating system uses electromagnetic fields to generate eddy currents within the patch material itself, which generates heat internally through resistive heating. This eliminates the need for external thermal blankets and achieves uniform heating through the patch thickness without significant heat loss to the environment.
2Ease of operation
If a thermal blanket is used to cure the patch, then the curing process can be performed on-site, but controlled curing of all points through the thickness is difficult
Solution Approach 1:
The patent replaces the thermal blanket heating method with induction heating technology. The induction heating system uses electromagnetic fields to generate eddy currents within the patch material itself, which generates heat internally through resistive heating. This eliminates the need for external thermal blankets and achieves uniform heating through the patch thickness without significant heat loss to the environment.
Solution Approach 2:
The patent employs adjustable induction heating parameters including frequency (e.g., 100-600 kHz), current amplitude, and coil positioning to control the heating process. By varying these parameters, the system can achieve uniform temperature distribution throughout the patch thickness while maintaining on-site repair capability.
3Manufacturing precision
If autoclaving is used to cure the patch, then controlled temperature and pressure conditions are provided, but the parent structure must be disassembled and transported
Solution Approach 1:
The patent replaces the autoclave method with induction heating technology. The induction heating system provides controlled heating directly at the repair location without requiring the parent structure to be disassembled or transported to a facility. The system achieves uniform heating and curing control while maintaining on-site repair capability.
4Use of energy by moving object
If conductive additives are added to the resin to enable induction heating, then the patch can be heated using electromagnetic fields, but the electrical, mechanical and thermal properties of the CFC are altered
Solution Approach 1:
The patent enables the carbon fibre composite patch itself to serve as the heating element through induction heating. The carbon fibres in the patch, which are naturally electrically conductive, generate eddy currents when exposed to electromagnetic fields, producing heat internally without requiring additional conductive additives. This maintains the original material properties while achieving heating capability.
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 approach enables efficient, uniform curing of carbon fibre composite repairs without altering the material's properties, reducing the need for disassembly and additional testing, and maintaining the integrity of the parent structure, while allowing for on-site repairs with simpler equipment.
Implementation Method 1
The coil induces a changing magnetic flux density in the patch, which in turn induces an eddy current perpendicular to the direction of the magnetic field in accordance with Faraday's Law
Implementation Method 2
The eddy current circulating through electrically conducting components of the patch raises the temperature by Joule heating
Data Source
AI summary
A procedure for repairing a polymer matrix composite component is provided. The procedure includes the steps of: providing a polymer matrix composite component having a site prepared for repair by removal of damaged or defective material; locating an uncured, polymer matrix composite repair patch at the site to re-build the component thereat; and curing the polymer matrix of the repair patch by heating the patch using eddy currents induced by one or more alternating current coils. The repair patch is without metallic additives, such that the repaired polymer matrix composite after the curing step is also without metallic additives in the vicinity of the repair patch.