Composite Duct Ring Joint Using Interference Fit Connection
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Solution Overview
Problem
Fiber-reinforced composite and metal matrix composite materials used in ducts often have poor bonding properties with adhesives and experience performance reductions when holes are drilled, making it challenging to achieve strong and reliable connections with other parts, such as metal components.
Innovation Solution
The apparatus consists of an inner and outer ring system with a conical axially extending portion and flanges, forming an interference fit and using a U-shaped coupling ring or snap rings to secure the duct in place, allowing for a friction fit and improved bonding through heat expansion and serrations for enhanced strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If fiber-reinforced composite materials or metal matrix composites are used to make lightweight ducts, then the weight of the duct is reduced, but the bonding properties with adhesives deteriorate and the performance reduces when holes are drilled
Solution Approach 1:
The patent introduces an intermediate joining apparatus consisting of an inner ring and outer ring system that acts as a mediator between the composite duct and metal parts. This intermediary mechanism avoids direct bonding or drilling into the composite material, instead using friction fits and mechanical interference fits to achieve reliable connections while preserving the lightweight composite structure.
Solution Approach 2:
The invention replaces chemical bonding (adhesives) and traditional mechanical fastening (drilling and bolting) with a mechanical interference fit system. The outer ring is heated to expand, then fitted over the inner ring assembly, creating a secure mechanical connection without requiring holes or adhesives in the composite duct.
2Ease of manufacture
If holes are drilled in composite materials to receive bolts for joining, then mechanical connection is achieved, but the performance significantly reduces due to stress concentrators
Solution Approach 1:
The invention extracts the joining mechanism from the composite duct itself by using separate inner and outer rings that attach to the duct surface without requiring holes through the composite structure. This removes the stress concentrators (holes) from the load-bearing composite material while maintaining connection capability.
Solution Approach 2:
The joining apparatus concentrates the mechanical connection forces at specific localized interfaces (between the rings and duct surface, and between the inner and outer rings) rather than requiring holes distributed through the composite structure. This localized approach preserves the overall structural integrity of the composite material.
3Adaptability or versatility
If conventional joining methods are used to connect ducts to metal parts, then connection is achieved, but the lightweight properties and material versatility are compromised
Solution Approach 1:
The joining apparatus is designed as a universal system that can connect various types of composite ducts to different metal parts without requiring material-specific modifications. The inner and outer ring design works with any composite duct that can accommodate the inner ring, enabling broad material compatibility across different composite types and applications.
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 solution provides a strong, durable connection for lightweight ducts made from composite materials, enabling reliable attachment to other parts while maintaining the lightweight properties of the materials, and allowing for the use of a wide range of dissimilar materials.
Implementation Method 1
A metal outer ring is then heated and slid over the outer surface of the shaft until it comes to a common axial position with the inner ring. The outer ring is then cooled so as to shrink it into an interference fit
Implementation Method 2
The inner surface of said outer ring abuts said outer surface of said inner ring at said second ends of said outer and inner rings
Data Source
Figure 1
Figure 2
Figure 3A~3D
AI summary
The present disclosure relates to an apparatus (10) for connecting to the end of a duct (40), the apparatus (10) comprising: an outer ring (12) having a central axis (C) and an inner surface (14) extending between a first (12a) axial end and a second axial end (12b) of the outer ring (12); and an inner ring (30) positioned within the outer ring (12) and having a central axis (C) and an outer surface (36) extending between a first (30a) and second (30b) axial end of the inner ring (30). A gap (50) is provided between the outer surface of the inner ring (30) at its first end (30a) and the inner surface of the outer ring (12) at its first end (12a), the gap (50) extending in the direction of the second ends (12b, 30b) of the inner and outer rings (12, 30). The gap at the first ends of the rings (12, 30) is configured to receive the duct (40) and the gap (50) decreases in width as it extends away from the first ends (12a, 30b) and in the direction of the second ends (12b, 30b). The apparatus further comprises an axial positioning means provided at the second ends of the outer (12) and inner rings (30), that is configured to retain the inner (30) and outer rings (12) in a fixed axial position relative to each other. A method for connecting this apparatus to the duct is also described. A system comprising more than one of these apparatuses (10, 10') is also described.