Thermoplastic Welding Thermal Gradient Control
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Solution Overview
Problem
Thermoplastic composite laminate welding via magnetic induction is inconsistent due to heat source intensity profiles, eddy current resistance variations, and inaccessibility of backing laminates, leading to melting or deformation of non-faying surfaces, and requires effective thermal management and pressure application to prevent deconsolidation.
Innovation Solution
A thermoplastic composite welding system utilizing a cooling element with a heat sink and an elastomeric pressure pad integrated with an induction coil, which creates a thermal gradient in the heat-side laminate to prevent melting and deformation, while an elastomeric pressure pad ensures compliance with textured surfaces and applies pressure for consistent welding, and in-situ electrical characteristic measurement adjusts welding parameters for optimal results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a magnetic induction heat source is positioned near a non-faying surface to weld thermoplastic composite laminates, then welding can be performed, but melting or deformation of the non-faying surface occurs due to inverse heat intensity to distance profile
Solution Approach 1:
The patent applies preliminary cooling action by positioning a heat sink in thermal contact with the non-faying surface before induction heating begins. This pre-cooling establishes a thermal gradient that prevents melting during subsequent heating, allowing the heat source to be positioned close to the non-faying surface without causing deformation
Solution Approach 2:
The heat sink acts as an intermediary thermal management component between the induction heat source and the laminate non-faying surface. It absorbs excess heat through thermal conduction while allowing the magnetic field to pass through, mediating the thermal interaction to prevent surface melting
2Object-affected harmful factors
If heat sinks made of electrically insulative and thermally conductive materials are positioned between the heat source and laminates to prevent melting, then melting is prevented, but such materials are rare, expensive, and/or difficult to process
Solution Approach 1:
Instead of using rare and expensive specialized materials, the patent employs a heat sink made from common, easily processable materials like aluminum or copper. The heat sink copies the required thermal management function using readily available materials that are simple to manufacture and integrate into the welding system
Solution Approach 2:
The patent changes the material selection parameters from rare, specialized electrically insulative and thermally conductive materials to common metals with high thermal conductivity. This parameter change maintains the melting prevention function while dramatically improving ease of manufacture and material availability
3Object-affected harmful factors
If heat sinks are used to prevent melting, then melting is prevented, but heat sinks increase the heat required and/or slow the welding procedure
Solution Approach 1:
The patent employs periodic or pulsed induction heating combined with continuous heat sink cooling. This periodic heating action allows thermal gradients to be maintained effectively, preventing melting while minimizing total heat input and maintaining welding speed
Solution Approach 2:
The heat sink is positioned in specific locations where thermal management is most critical, rather than covering entire surfaces. This localized thermal management prevents melting at critical areas while minimizing overall heat absorption, maintaining welding efficiency
4Reliability
If pressure is applied during welding to prevent deconsolidation, then deconsolidation is prevented, but eddy current resistance varies due to laminate compaction and geometry changes
Solution Approach 1:
The patent incorporates sensors to monitor temperature, pressure, and eddy current resistance during welding, with real-time feedback control adjusting heating power and pressure to maintain consistent weld quality despite variations in laminate compaction and geometry
Solution Approach 2:
The welding system employs dynamic adjustment of heating power and pressure based on real-time conditions. Pressure and heating parameters are continuously adapted during the welding process to account for eddy current resistance variations caused by laminate compaction and geometry changes
5Ease of operation
If the backing or substructure laminate is inaccessible during welding, then tooling and support structures cannot be inserted, but pressure application to prevent deconsolidation becomes difficult
Solution Approach 1:
The heat sink serves dual functions: it cools the non-faying surface to prevent melting and simultaneously provides a rigid backing structure that transmits compression pressure during welding. This self-service approach eliminates the need for separate support tooling in inaccessible locations
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 system effectively welds laminates without melting or deforming non-faying surfaces, ensuring consistent weld quality by managing thermal gradients and pressure distribution, and allows for real-time adjustment of welding parameters to accommodate material variations, enhancing weld strength and consistency.
Implementation Method 1
magnetic induction heat source
Implementation Method 2
eddy current resistance variation in the laminates
Implementation Method 3
heat flux quantity/distribution
Implementation Method 4
heat sinks made of electrically insulative and thermally conductive materials
Implementation Method 5
thermal gradient in the laminate near the heat source
Data Source
AI summary
A system and method for thermoplastic composite welding comprising a cooling means and a heat source. The cooling means cools a heat-side laminate so as to create a thermal gradient in the heat-side laminate. The heat source heats the heat-side laminate after the cooling step is initiated but before the thermal gradient dissipates so that a first side of the heat-side laminate closer to the heat source does not deform as faying surfaces of the heat-side laminate and another laminate farther away from the heat source are welded together.