Friction Stir Welding Fiber-Reinforced Thermoplastics
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Solution Overview
Problem
Current methods for joining fiber-reinforced thermoplastic aircraft parts, such as riveting and traditional bonding, are time-consuming, structurally weakening, and non-optimal in terms of weight and load distribution, while also requiring elaborate cleaning and potentially hazardous processes.
Innovation Solution
A method using friction stir welding with a device featuring a rotating friction shoulder and stirring pin to mix fiber-containing plastic material into the joining zone, eliminating the need for rivet bores and extensive cleaning, and allowing for automated, high-quality bonding with optimized load flow and weight distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If riveting methods are used to join fiber-reinforced thermoplastic parts, then structural connection is achieved, but structural weakening occurs due to rivet bores, torn fibers, and delaminations
Solution Approach 1:
The patent replaces the mechanical riveting system with a friction stir welding system that uses friction-generated heat to plasticize and join thermoplastic parts. This substitution eliminates rivet bores and associated structural damage while maintaining strong structural connection through controlled thermal processing and material intermixing.
Solution Approach 2:
The patent changes the joining approach from cold mechanical fastening to thermal processing by controlling temperature parameters. The friction stir welding process heats the thermoplastic matrix to its melting point, allowing material flow and bonding, then cools it to create a strong joint without structural weakening.
2Strength
If riveting methods are used to join fiber-reinforced thermoplastic parts, then structural connection is achieved, but the process is very time-consuming due to multiple manual steps
Solution Approach 1:
The friction stir welding tool performs multiple functions automatically during a single continuous operation: it generates friction heat, stirs and plasticizes the material, mixes fibers, and creates the joint all in one self-contained process. This eliminates the need for separate manual steps for alignment, drilling, cleaning, and fastening.
Solution Approach 2:
The patent combines multiple separate joining operations (heating, stirring, mixing, and bonding) into a single integrated friction stir welding process. This merging of functions into one tool and one continuous operation dramatically reduces cycle time while maintaining joint quality.
3Strength
If bonding methods are used to join fiber-reinforced thermoplastic parts, then structural connection is achieved, but elaborate cleaning measures and strict safety regulations are required
Solution Approach 1:
The patent replaces chemical bonding methods with a mechanical-thermal friction stir welding process. This substitution eliminates the need for adhesive cleaners, solvents, and safety regulations associated with chemical handling, while achieving strong structural bonds through controlled material plasticization and intermixing.
4Strength
If material overlap is used in riveting and bonding methods, then structural connection is achieved, but weight is not optimized and steplike load flow is created
Solution Approach 1:
Instead of using overlapping joints that create step-like transitions, the patent inverts the approach by using a butt joint configuration where parts meet end-to-end. The friction stir welding process fills the joint interface with plasticized material, creating a smooth, continuous load path without weight-penalty overlaps.
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 short cycle times, high reproducibility, and increased seam strength without structural weakening, maintaining the integrity of the parts' properties and achieving a lightweight, load-optimized construction with a seamless load flow.
Implementation Method 1
a friction stir tool with a friction shoulder and with a stirring pin that are able to rotate in the same direction about a vertical tool axis. The friction shoulder and the stirring pin are able to be displaced along the vertical tool axis such that the friction shoulder can be spaced apart from the joining zone and carry out a lifting motion
Implementation Method 2
a rotating stirring pin for intermixing plasticized material
Implementation Method 3
The friction shoulder and the stirring pin are able to be displaced along the vertical tool axis such that the friction shoulder can be spaced apart from the joining zone and carry out a lifting motion
Data Source
Figure 1~3
Figure 4
AI summary
Disclosed is a method for producing a bonded joint between fiber-reinforced thermoplastic parts (2, 4) to be joined, in which fiber-containing plastic material (22) is mixed into the joining zone while friction stir welding the parts (2, 4) to be joined in the form of a butt joint, as well as a device for carrying out such a method and a thusly joined component.