Slotted Composite Tube Joints to Prevent Bunching and Cracking
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Solution Overview
Problem
Composite tube assemblies formed from carbon fiber materials face challenges such as material bunching and cracking during the forming process, especially when using higher cure temperature resins, which complicates the manufacturing process and makes it difficult to achieve the glass transition temperature range.
Innovation Solution
The method involves forming a composite tube with axial slots at the end, which are radially compressed over a tapered fitting, allowing for the arms to be connected without overlapping, and optionally using a bolstering structure to retain the arms against the tube's outer surface, enabling lower temperature forming and reducing material stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the composite tube end is compressed over a fitting to form the assembly, then the tube end forms around the fitting, but material bunching occurs and CF material cracks
Solution Approach 1:
The composite tube end is divided into multiple segments by cutting slots through the thickness, creating discrete arms that can independently deform during compression. This segmentation prevents material bunching and cracking by allowing each arm to conform to the fitting shape separately, resolving the contradiction between ease of forming and manufacturing precision.
Solution Approach 2:
Slots are cut into the tube end before the compression forming operation, preparing the material in advance to accommodate the forming process. This preliminary action enables the arms to flex and conform to the fitting without cracking, addressing both the ease of manufacture and material integrity concerns.
2Ease of manufacture
If post processing is performed to clean up the formed area, then the composite tube assembly is completed, but complexity and risk to the manufacturing process increase
Solution Approach 1:
The harmful excess material is removed during the slot cutting process rather than requiring separate post-processing operations. By extracting the problematic material beforehand through precise slot cutting, the forming process produces a clean finished product, reducing manufacturing complexity while completing the forming operation.
3Strength
If higher cure temperature resins are used, then composite material strength increases, but it becomes more difficult to achieve the glass transition temperature range and compress the tube end
Solution Approach 1:
By segmenting the tube end into arms through slot cutting, the forming process can proceed at lower temperatures since each arm can be compressed independently. This segmentation reduces the overall forming difficulty while maintaining the use of high-strength higher cure temperature resins, resolving the contradiction between material strength and ease of manufacture.
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 minimizes material bunching, reduces the need for post-processing cleanup, and allows for the use of composite materials with higher glass transition temperatures, simplifying the manufacturing process and maintaining tolerance accuracy.
Implementation Method 1
radially compressing each of the arms over the fitting annular tapered outer surface, such that the two edges of each slot do not overlap each other
Implementation Method 2
obtaining a fitting including a first end opposite a second end. The fitting also includes an annular tapered outer surface tapering from a first diameter at, or proximate, the first end to a second diameter
Data Source
AI summary
A method of forming a tube assembly includes forming arms on a tube end portion by forming a plurality of slots or slits on such tube end and mating such arms with a tapered outer surface of a fitting. The fitting may include at least one annular step mated with an annular step formed on the tube inner surface.