Thermoplastic Composite Welding with Localized Heating and Cooling
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Solution Overview
Problem
The high temperature welding of stiffeners onto composite panels with thermoplastic matrices poses challenges due to the need for complex and expensive tooling, especially for aircraft components, as existing methods struggle with thermal expansion and uniform pressure application, limiting the use of thermoplastic composites for large stiffened panels.
Innovation Solution
A device utilizing localized heating of the stiffener's sole and cooling of the anvil, combined with controlled clamping pressure, allows for efficient welding while minimizing tooling costs and thermal inertia, enabling uniform pressure and controlling the heat-affected zone to maintain the structural integrity of the composite material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the entire section of the stiffener is subjected to pressure during bonding, then the bonding is achieved, but the tooling complexity increases due to the need to support hollow sections with cores
Solution Approach 1:
The bonding process is segmented into localized zones rather than applying pressure to the entire stiffener section. The punch and anvil are positioned to apply pressure only at specific bonding interfaces, eliminating the need for cores in hollow sections and reducing tooling complexity while maintaining bonding quality.
Solution Approach 2:
Instead of uniform pressure application across the entire stiffener, the invention applies pressure locally at the bonding interfaces using a punch and anvil. This localized approach achieves the necessary bonding quality without requiring complex support structures for hollow sections.
2Reliability
If the thermoplastic matrix is heated to above its melting point for welding, then the welding of stiffener to skin is achieved, but the tooling complexity increases due to thermal expansion control requirements
Solution Approach 1:
The heating process is segmented to affect only the local bonding zone rather than the entire component. The punch and anvil are heated locally, allowing welding at the interface without requiring the entire tooling to withstand and control thermal expansion at high temperatures, thus reducing tooling complexity.
Solution Approach 2:
Temperature is applied locally at the bonding interface through the heated punch and anvil rather than heating the entire component. This localized thermal approach achieves welding quality while minimizing thermal expansion issues and reducing tooling complexity requirements.
3Reliability
If the thermoplastic matrix is heated to melting point for welding, then the assembly is achieved, but the cycle time increases due to the need to control volume expansion and maintain reinforcement placement
Solution Approach 1:
The thermal process is segmented to heat only the bonding zone locally through the punch and anvil. This localized heating achieves the necessary matrix melting and welding quality while significantly reducing the time required compared to heating entire components, thus reducing cycle time.
Solution Approach 2:
Heating is applied locally at the bonding interface rather than to the entire component. This approach achieves reliable assembly by melting the matrix only where needed while minimizing the time required for thermal processing and reducing overall cycle time.
4Manufacturing precision
If localized heating of the stiffener sole and cooling of the anvil is used, then the heat-affected zone is minimized and uniform pressure is achieved, but the process complexity increases
Solution Approach 1:
The invention applies different thermal conditions to different parts of the tooling: the punch is heated locally to melt the matrix at the bonding interface, while the anvil is cooled to minimize the heat-affected zone in the skin. This differential local quality approach achieves precise heat control and uniform pressure distribution.
Solution Approach 2:
The anvil is pre-cooled before and during the bonding process to counteract the heat transferred from the heated punch. This preliminary anti-action prevents excessive heat diffusion into the skin, minimizing the heat-affected zone and achieving precise thermal control.
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 enables efficient high-temperature welding of stiffeners onto composite panels with thermoplastic matrices, reducing tooling costs and cycle times, while ensuring uniform pressure and maintaining the nominal compactness of the composite material, thus overcoming the limitations of existing technologies.
Implementation Method 1
activating the heating element so as to bring the part of the sole exposed to the heating to a temperature Tf equal to or greater than the melting temperature of the matrix
Implementation Method 2
bring the part of the sole exposed to the heating to a temperature Tf equal to or greater than the melting temperature of the matrix
Implementation Method 3
cooling of the anvil, the device which is the subject of the invention makes it possible to heat in a localized manner the interface between the sole of the stiffener and the skin
Data Source
Figure 1~2
Figure 3~5
AI summary
The invention relates to a device for welding the base plate (125) of a stiffener (120) to the face of a skin (110), the stiffener (120) and said skin (110) being constituted of a composite comprising a thermoplastic polymer matrix, characterized in that it comprises: a. a punch (220) comprising a part that forms a press table, the cross-sectional width of which is less than or equal to the width of the base plate (125) of the stiffener and a heating element (225, 226) having a width smaller than the width of the press table; b. an anvil (210), the cross-sectional width of which is smaller than the width of the skin, which anvil comprises cooling means; c. pressing means (251, 252) capable of carrying out a clamping between the punch and the anvil. The invention also relates to a process implementing this device.