Composite Joint Preload Eliminates Fretting Wear
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Solution Overview
Problem
Joining composite structural components to metallic end fittings is challenging due to fretting and wear issues, especially in aerospace applications, where a reliable and robust joint is required to transmit axial loads efficiently while maintaining a high strength-to-weight and strength-to-cost ratio.
Innovation Solution
A twin-member composite structural component with preloaded compressive and tensile stress in the axial direction, eliminating the need for bonding or complex mechanical forms, and utilizing a mechanical joint that constrains the end fitting to prevent relative movement and fretting, thereby optimizing the polymer matrix composite material for axial load transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a mechanical joint is used to join composite structural component to metallic end fitting, then axial load transmission is achieved, but fretting and wear occur due to relative movement between the metal end fitting and the relatively soft composite material
Solution Approach 1:
The patent applies preliminary action by preloading the composite structural component with compressive stress before service loading occurs. This preload ensures that the component remains in continuous contact with the metallic end fitting, eliminating relative movement and preventing fretting wear during tension and compression cycles.
Solution Approach 2:
The patent changes the stress state parameter of the composite component from unstressed to preloaded compressive state. This parameter change modifies the contact conditions between the composite and metal, ensuring continuous contact and eliminating the harmful relative movement that causes fretting.
2Force
If bonding or complex mechanical forms are used for the end fitting, then load transmission may be improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts the complex bonding or mechanical form requirements from the end fitting design. By using a preload mechanism, the joint achieves reliable load transmission through simple bearing contact, eliminating the need for complex end fitting geometries or bonding systems.
Solution Approach 2:
The patent replaces complex mechanical forms (such as threaded connections, keyed joints, or bonded interfaces) with a simpler preload-based bearing contact system. This substitution maintains load transmission efficiency while significantly reducing manufacturing complexity.
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 high strength-to-weight ratio, minimizes fretting wear, and allows for mass savings by tailoring the joint's geometry and material properties to specific loading conditions, ensuring reliable axial load transmission without the need for sophisticated manufacturing or bonding.
Implementation Method 1
the first and second members are preloaded with compressive/tensile stress in the axial direction of the composite structural component
Implementation Method 2
mechanical joints can often suffer from the problem of fretting and wear due to relative movement between the metal end fitting and the relatively soft material of the composite structural component
Data Source
Figure 1~1E
Figure 2~2E
Figure 3~3D
AI summary
A composite structural component 2 comprises an elongate member made of a polymer matrix composite material, the elongate member generally extending along an axis of the composite structural component 2 from an end portion 5 thereof. The composite structural component 2 also comprises an end fitting 8 that forms a mechanical joint with the end portion 5. The elongate member comprises a first member 4 extending from the end portion 5 along the axis of the composite structural component 2 and a second member 3 extending from the end portion 5 along the axis of the composite structural component 2. The end fitting 8 is constrained in the end portion 5 by the first and second members 4,3 such that the first member 4 is preloaded with a compressive stress in the axial direction and the second member 3 is preloaded with a tensile stress in the axial direction.