Composite Tube Assembly Tapered Fitting Thermal Stress
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Solution Overview
Problem
Carbon composite tube assemblies connected to metallic end fittings experience stress and weakening due to differing thermal expansion rates, leading to a fragile connection over time.
Innovation Solution
A composite tube assembly design featuring a fitting with a tapered outer surface and a bolstering structure, including a reduced diameter portion for adhesive bonding and a wrap or collar for mechanical reinforcement, to create a robust connection between the composite tube and the fitting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metallic end fitting is directly connected to a carbon composite tube, then the connection is simple and lightweight, but the connection strength deteriorates over time due to thermal expansion differences
Solution Approach 1:
A fitting with a tapered outer surface section is introduced as an intermediary component between the metallic end fitting and the carbon composite tube. This fitting accommodates thermal expansion differences through its geometric design and material selection, preventing direct stress transmission between the metallic end fitting and the tube while maintaining connection integrity over time.
Solution Approach 2:
The solution employs a composite structure combining metallic materials (end fitting), polymer materials (fitting with tapered section), and carbon composite materials (tube). This multi-material approach allows each component to be optimized for its specific function while collectively resolving the thermal expansion incompatibility between metal and carbon composite.
2Reliability
If the fitting has a complex structure with tapered sections and bolstering, then the connection robustness is improved, but the manufacturing complexity increases
Solution Approach 1:
The fitting incorporates a tapered outer surface section with continuous curvature that transitions smoothly between different diameter portions. This curved geometry accommodates thermal expansion through elastic deformation while maintaining structural integrity, and can be manufactured using standard forming processes for polymer components.
Solution Approach 2:
The fitting features localized structural variations including a reduced diameter portion for adhesive bonding and a tapered outer surface section for mechanical reinforcement. These local modifications are concentrated only where needed to achieve connection robustness, rather than requiring complex structures throughout the entire fitting.
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
The solution enhances the mechanical strength and durability of the connection by accommodating thermal expansion differences and preventing separation between the composite tube and the fitting, ensuring a stable and long-lasting assembly.
Implementation Method 1
a groove to accommodate an adhesive or a resin bonding the composite tube to said fitting
Implementation Method 2
carbon composite may have a rate of thermal expansion and/or negative thermal expansion (i.e. contraction) substantially different from that of the metallic end fitting
Data Source
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AI summary
The inventions provides for a composite tube assembly comprising: a composite tube (10') comprising an end; a fitting (12') comprising a first end (122') opposite a second end (127), said fitting second end (127) comprising a first outer diameter, wherein said fitting (12') comprises a tapered outer surface section (128') between said first and second ends (122', 127), said tapered outer surface section (128') tapering radially inward to a smaller diameter in a direction toward the first end (122'), wherein said fitting (12') penetrates a portion of said tube (10') through said tube end, wherein said second end (127) and said tapered outer surface section (128') are interior of the tube (10'), wherein said tube portion penetrated by said fitting (12') comprises a section mated to the tapered outer surface section (128') of the fitting (12'), wherein the fitting (12') comprises a constant diameter outer surface section (124') extending from the second end (127) to the tapered outer surface section (128'); and a bolstering structure (19', 21') surrounding and engaging said composite tube section.