Composite Tube Interference Joint with Recess Locking
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Solution Overview
Problem
Existing methods for joining metal and fibre reinforced composite tubes are prone to failure due to contamination, surface roughness, fatigue, and differential thermal expansion, leading to mechanical separation and sealing issues.
Innovation Solution
A composite tube design featuring a mating interface with both interference and clearance fits, utilizing a settable compound within a combined recess to form an internal locking element, which secures the tube sections together mechanically and provides a fluid seal, independent of adhesive bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive bonding is used to join metal and composite parts, then mechanical security and sealing are achieved, but the joint becomes highly sensitive to surface contamination and roughness, requiring careful surface preparation
Solution Approach 1:
The patent introduces a recess at the mating interface that receives a settable compound (adhesive or epoxy). This recess acts as an intermediary that contains the adhesive, ensuring it remains positioned correctly during assembly and curing. The recess protects the adhesive from contamination and provides a controlled environment for bonding, eliminating the need for extensive surface preparation while maintaining strong joint strength.
Solution Approach 2:
The recess is pre-formed in the mating interface before assembly occurs. This preliminary structural feature prepares the interface in advance to receive and contain the settable compound, ensuring proper adhesive placement and distribution without requiring complex surface preparation steps during the assembly process.
2Strength
If adhesive bonding is used to join metal and composite parts, then mechanical security is achieved, but the joint becomes susceptible to fatigue damage from thermal cycling and vibration
Solution Approach 1:
The patent changes the geometric parameters of the mating interface by introducing a recess that contains the adhesive. This geometric modification allows the adhesive to be confined in a controlled volume, creating a more uniform stress distribution that reduces fatigue loading on the bond line. The recess structure enables the joint to better accommodate thermal cycling and vibration without compromising reliability.
3Object-affected harmful factors
If O-rings are used to seal between metal and composite parts, then sealing is provided, but minimum material thickness is required for grooves and the seal is susceptible to separation under axial loads
Solution Approach 1:
The patent replaces the O-ring mechanical sealing system with a settable compound filling the recess at the mating interface. This substitution eliminates the need for O-ring grooves and the associated minimum material thickness requirements. The settable compound creates a direct structural seal that is integrated into the joint assembly, providing sealing capability without the complexity and space requirements of traditional O-ring systems.
4Strength
If interference fit is used to mechanically secure tube sections, then structural bond is achieved, but differential thermal expansion between metal and composite creates high strain on the adhesive bond
Solution Approach 1:
The patent segments the mating interface into distinct functional zones: an interfering portion for mechanical security and a clearance portion for accommodating thermal expansion. The recess is strategically positioned to receive the settable compound in the clearance zone, allowing differential thermal expansion between metal and composite materials without creating excessive strain on the adhesive bond.
Solution Approach 2:
The patent applies different fit characteristics to different portions of the mating interface. The interfering portion provides local mechanical security through interference fit, while the clearance portion allows local thermal expansion accommodation. The settable compound in the recess provides localized bonding without transmitting excessive thermal strains across the entire interface.
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 provides a robust, fatigue-resistant, and sealed joint that maintains mechanical and fluid integrity across varying pressures, temperatures, and load conditions, while being insensitive to surface preparation and thermal expansion differences.
Implementation Method 1
a settable compound can be disposed during assembly to form an internal locking element that assists the interference fit by mechanically securing together the first and second tube sections
Implementation Method 2
each of the respective mating interfaces having an interfering portion and a clearance portion to respectively create an interference fit and a clearance fit between the first and second tube sections
Data Source
Figure 1~2
Figure 3~5
Figure 6
AI summary
A composite tube comprises a first tube section (100) and a second tube section (200), at least one of which is of fibre reinforced composite form, a mating interface (20, 30) being provided on each of the first and second tube sections (100, 200), each of the respective mating interfaces (20, 30) having an interfering portion (2, 9) to create an interference fit between the first and second tube sections (100, 200) when the composite tube is assembled, each of the mating interfaces (20, 30) being configured with a recess (3, 8), the recesses (3, 8) being alignable with one another, during assembly, to define a combined recess (13) when the composite tube is assembled, into which a hardened settable compound can be disposed during assembly to form an internal locking element (13a) that assists the interference fit by mechanically securing together the first and second tube sections (100, 200).