Thermoplastic Composite Bicycle Frame Joint Integrity
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Solution Overview
Problem
Existing methods for manufacturing bicycle frames using fiber reinforced composites face challenges such as poor recyclability and repairability of thermoset materials, complex and costly molds, reduced strength at seams in thermoplastic joints, and inconsistent surface finishes, particularly when joining parts of different diameters.
Innovation Solution
A method involving the fusion of thermoplastic fiber reinforced composite parts, where a first hollow tube part and fiber reinforced shell parts are joined by heating above the softening temperature and consolidating under pressure to form a strong, lightweight, and stiff monocoque frame with a continuous fiber structure across the seam, allowing for flexible frame design and reduced manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thermoset composite materials are used to join pre-manufactured parts, then the parts can be interconnected in a heating step, but the joints negatively affect the performance of the formed product in terms of stiffness and strength, allowing cracking and failure at said joints under heavy loads
Solution Approach 1:
The patent changes the material parameter from thermoset to thermoplastic composite, which allows the material to be reprocessed and reformed. This parameter change enables the fiber reinforcement to continue across the joint area, maintaining structural integrity and strength while still allowing for manufacturing flexibility.
Solution Approach 2:
The patent uses fiber reinforced thermoplastic composite materials where fibers are embedded in a thermoplastic matrix. This composite structure allows the fibers to span across joint areas continuously, providing strength and stiffness while the thermoplastic matrix enables reprocessing and reforming capabilities.
2Strength
If fiber reinforced sheets are provided across a seam of preformed shell parts to improve the strength of a fused part, then the strength may be improved, but the outer appearance of the finalized product at the joint is negatively affected, requiring surface finishing processes
Solution Approach 1:
The patent incorporates fiber reinforcement into the shell parts themselves during their initial formation, rather than adding separate reinforcement sheets later. This preliminary action ensures continuous fiber coverage across future joint areas and eliminates the need for additional surface finishing operations.
Solution Approach 2:
The patent merges the structural reinforcement function with the cosmetic surface function by ensuring that the fiber reinforcement is integrated into the shell parts in a way that provides both strength and an acceptable appearance without requiring separate surface finishing operations.
3Adaptability or versatility
If the effect of provision of fiber reinforced strips is limited and/or inconsistent, then bicycle parts having joints between parts of different diameter have insufficient strength at the seams
Solution Approach 1:
The patent applies local quality by ensuring that fiber reinforcement is specifically positioned and continuous at joint areas, with fiber orientation and density optimized for the local stress conditions. This allows the structure to adapt to different diameter joints while maintaining consistent strength through locally optimized fiber placement.
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 enhances the strength and surface finish of the interconnects between frame parts, improves manufacturability, and allows for the creation of lightweight, stiff bicycle frames with improved joint integrity and reduced need for dedicated molds, suitable for various frame designs and sizes.
Implementation Method 1
heating the first hollow tube part and the fiber reinforced shell parts at least at a position of the overlap to a temperature above a softening temperature of the first and second thermoplastic fiber composite
Implementation Method 2
consolidating the heated first and second thermoplastic fiber composite by pressure to form a fused interconnect between the hollow tube parts
Data Source
AI summary
The present invention relates to a bicycle frame (100) and a method of production thereof. In one embodiment the bicycle frame (100) comprises a first hollow tube part (10) comprising a first thermoplastic fiber reinforced composite comprising a thermoplastic matrix and an embedded structure of fibers (11, 12); and a second hollow tube part (20) comprising at least a first fiber reinforced shell part (21) and a second fiber reinforced shell part (22) each comprising a second thermoplastic fiber composite. According to the method a fused interconnect is formed having an overlap (30) between the first hollow tube part (10) and the second hollow tube part (20), wherein the embedded structure of fibers (11, 12) of the first hollow tube part (10) at the overlap (30) crosses an overlap (30) between the hollow tube parts (10, 20).