Composite Torque Tube Interference Fit and Adhesive Bonding
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Solution Overview
Problem
The challenge in automotive engineering is to effectively connect carbon fiber composite materials to traditional metallic components, such as engine bell housings and transaxle components, without compromising strength, reliability, or crash worthiness, as existing methods like fasteners, welding, and adhesive bonding face issues like high costs, interference fits, and creep deformation at elevated temperatures.
Innovation Solution
A drive train system featuring a composite tube with an internal metallic support tube in an interference fit, combined with an adhesive bond, where the support tube and hub are also in an interference fit, and a relief space for adhesive injection in the press-fit joint, allowing self-fixturing during curing without external fixtures, thereby enhancing the connection's strength and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a carbon fiber/epoxy tube is pressed fit into a metallic bell housing, then weight reduction is achieved, but the composite may creep under temperature and compromise the interference fit
Solution Approach 1:
An adhesive layer is introduced as an intermediary between the carbon fiber composite tube and the metallic bell housing. This adhesive mediator prevents direct metal-composite contact that would cause creep, while still providing a reliable bonded connection. The adhesive accommodates thermal expansion differences and prevents the composite from creeping under under-hood temperatures.
Solution Approach 2:
The surface properties of the composite tube are modified through machining an undercut and applying adhesive, changing the interface characteristics from a simple interference fit to a bonded joint with mechanical interlocking. This parameter change in the connection mechanism prevents creep while maintaining the weight benefits of composite materials.
2Ease of manufacture
If adhesive is applied to a carbon fiber tube and slipped fit into housing, then installation is simplified, but adhesive is scraped off during installation compromising bond strength
Solution Approach 1:
An undercut is machined into the bell housing bore before the composite tube is installed. This preliminary action creates a mechanical interlock feature that prevents the composite tube from being inserted too far, thereby preventing adhesive scrape-off while still allowing for simplified slipped-fit installation. The undercut acts as a physical stop that preserves adhesive bond integrity.
3Strength
If fasteners are used to tie metallic and composite components together, then connection strength is improved, but cost increases and high volume production becomes less attractive
Solution Approach 1:
The adhesive bonding process merges the connection function into a single continuous joint, eliminating the need for multiple discrete fasteners. This consolidation reduces part count, simplifies assembly, and lowers cost while maintaining connection strength. The adhesive bond distributes loads continuously across the joint interface rather than concentrating forces at discrete fastener locations.
4Ease of manufacture
If welding is used to connect components, then cost effectiveness is improved, but it becomes impossible for composite materials
Solution Approach 1:
The welding process (thermal-mechanical system) is replaced with an adhesive bonding process (chemical-mechanical system). This substitution enables joining of composite materials that cannot be welded, while adhesive bonding can be performed at lower costs suitable for high-volume automotive production. The adhesive provides both chemical adhesion and mechanical interlocking through the undercut feature.
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 prevents creep deformation and ensures a robust, cost-effective connection suitable for high-volume automotive production by maintaining the strength and reliability of the composite material while allowing for weight reduction and improved load-bearing capabilities.
Implementation Method 1
the support tube and the composite tube are in an interference fit
Implementation Method 2
the composite could creep when subjected to under the hood and road temperatures
Implementation Method 3
adhesive bond is applied to bond the composite tube and the engine component together
Data Source
AI summary
A composite tube made from a combination fiber and epoxy is disclosed. The tube may be made by filament winding although other materials and processes are suitable. In one example, the tube laminate is a mix of axial and helical fibers tailored to meet the stiffness and strength requirements of the particular application. Fibers having a different modulus may also be mixed to meet axial and torsional stiffness requirements. For example, high modulus fibers may be used in a helical pattern to handle high torque loads while lower modulus fibers may be used for the remaining portion of the tube laminate. The composite tube may be used for load and/or torque bearing applications and can include a support tube pressed fit into an end of the tube.