Laser Joining of Carbon Fiber Thermoplastics via Scarf Joint
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Solution Overview
Problem
Existing joining technologies for thermoplastic workpieces, such as transmission laser welding and induction welding, face challenges with material transparency requirements, energy decoupling issues in carbon fibers and copper mesh, and limitations in process control due to overall warming and thickness constraints.
Innovation Solution
A joining process that involves creating a facility area on the workpieces by tracing fibers or applying a microstructured functional layer, positioning the workpieces to form a seam area with a production gap, and inserting a connecting body that is heated locally using a laser to form a strong bond between the workpieces and the connecting body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transmission laser welding is used to join thermoplastic workpieces, then the joining process can be automated and performed at high speed, but the workpieces must be largely transparent and this causes overall heating and laser diffusion that significantly impact process control and speed
Solution Approach 1:
The patent applies local quality by transitioning from transmission laser welding that heats the entire workpiece to contact laser welding that heats only the specific joining zone. The laser beam is directed through a die to contact only the workpiece edges at the joining location, creating a localized melting zone without overall heating of the transparent workpieces, thus improving process control while maintaining joining speed
Solution Approach 2:
The patent introduces a die as an intermediary component between the laser source and the workpieces. The die serves as a mediator that guides and focuses the laser beam to contact only the specific joining surfaces, enabling precise control of the heating zone and eliminating the need for workpiece transparency while maintaining high-speed automated joining
2Adaptability or versatility
If induction welding is used to join thermoplastic workpieces, then the joining process can be performed on opaque materials, but energy couples into carbon fibers and copper braid for lightning protection causing overall heating and limitations for process control
Solution Approach 1:
The patent applies local quality by using contact laser welding instead of induction welding. The laser energy is delivered directly to the joining zone through the die, creating a highly localized melting zone. This eliminates the diffuse energy coupling into carbon fibers and copper braid that occurs with induction welding, enabling precise process control while working with opaque fiber-reinforced thermoplastic materials
Solution Approach 2:
The patent replaces the induction welding electromagnetic field mechanism with a direct contact laser heating mechanism. Instead of using electromagnetic induction that couples energy into conductive elements throughout the workpiece, the system uses a laser beam delivered through a die to directly melt and join the workpiece edges, providing superior process control and eliminating unwanted energy absorption by reinforcement fibers
3Manufacturing precision
If the melting zone is reduced to improve process control and avoid distortions, then joining precision is improved, but the joining process may become more complex and time-consuming
Solution Approach 1:
The patent applies universality by designing a die that serves multiple functions simultaneously: it guides the laser beam to the joining zone, applies mechanical pressure to the workpiece edges, and defines the joining geometry. This multi-functional approach enables precise localized heating without increasing overall process complexity, as the die integrates several functions into a single component
Solution Approach 2:
The patent merges the laser delivery system, pressure application system, and joining geometry definition into a single integrated die component. By combining these functions into one element, the system achieves precise localized heating and joining without the complexity of separate systems for each function, maintaining simplicity while improving joining precision
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 process enables improved control and speed in joining thermoplastic workpieces, particularly those with fiber-reinforced plastics, by reducing the melting zone and avoiding distortions, thus enhancing the robustness and efficiency of the joining process.
Implementation Method 1
heating the part of the connecting body located in the seam region by means of local heat input
Implementation Method 2
the connecting body is pressed by means of a pressing device which grips the connecting body and a counter-pressing device which grips the workpiece
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
To enable the joining of non-transparent carbon fiber reinforced plastic parts by laser welding, a joining method for connecting at least two thermoplastic workpieces (26) is proposed in which a scarf joint is created at the edge regions of the workpieces (26), and the workpieces (26) are then positioned relative to each other such that the opposing scarf joint regions define a weld area (60). Connecting elements (28) are then inserted into the weld area (60) and heated by local heat input from a laser beam (42) so that a strong, material-bonded connection is formed between the workpieces (26) and the connecting elements (28).