Grooved Composite-Metal Joint Liners for Torsional Load Transfer
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Solution Overview
Problem
Composite/metal joints in drive shafts experience significant stress concentrations under heavy torsional loads, leading to potential damage and failure due to the weak shear strength of composite materials, particularly at the interfaces with metallic components.
Innovation Solution
The introduction of cylindrical liners with grooves around fasteners, made of a softer material than the composite, allows for local deformation and uniform load distribution, reducing stress concentrations and enhancing load transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If radial fasteners are used to secure metallic sleeve to composite shaft, then the joint can transfer torsional loads, but stress concentrations occur at the corners of contact between fasteners and composite shaft leading to potential damage
Solution Approach 1:
A cylindrical liner is introduced as an intermediary component between the fastener and the composite shaft. The liner extends into the aperture of the composite shaft and has its own aperture for receiving the fastener. This mediator distributes the localized contact stresses from the fastener over a larger area of the composite shaft wall, reducing stress concentrations at the corners while maintaining effective load transfer capability.
2Force
If thick walls are used in composite shaft to accommodate heavy duty torsional loads, then the shaft can handle higher torque, but stress concentrations are amplified at the fastener-composite interface
Solution Approach 1:
The cylindrical liner acts as a stress-distributing intermediary that decouples the fastener from direct contact with the composite shaft wall. By introducing this intermediate layer, the localized high stresses that would otherwise concentrate at the sharp corners of the fastener-composite interface are redistributed over the broader contact area between the liner and the composite shaft, thereby reducing the stress concentration ratio even under heavy torsional loads.
3Device complexity
If fewer fasteners are used, then the device complexity is reduced, but the load transfer capability and reliability of the joint deteriorate
Solution Approach 1:
The cylindrical liner enhances the efficiency of each individual fastener by improving the stress distribution in the composite shaft. This allows for reduced fastener quantities while maintaining joint integrity, as each fastener can effectively utilize the full capacity of the composite shaft wall without being compromised by localized stress concentrations at the interface.
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3A~3D
AI summary
A composite/metal joint includes a composite member, a metallic member, a cylindrical liner, and a fastener (18). The composite member has a first aperture (28). The metallic member is disposed adjacent to the composite member and has a second aperture (30) coaxially aligned with the first aperture (28). The cylindrical liner extends longitudinally from a first end to a second end. The cylindrical liner has a cylindrical outer liner surface and a longitudinally extending third aperture coaxial with the first and second apertures (28, 30) and defined by an inner liner surface. The cylindrical liner is disposed in the first and second apertures with the outer liner surface adjacent to aperture walls of the first and second apertures. The cylindrical liner has a plurality of grooves intersecting the outer liner surface. The fastener (18) is disposed through the third aperture of the cylindrical liner and is configured to attach the metallic member to the composite member. An outer surface of the fastener (18) is in direct contact with the inner liner surface.