Thermoplastic Composite Torque Shaft Interference Fit
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Solution Overview
Problem
Existing composite torque drive shafts face issues with metallic end fittings causing slip and stress concentration leading to failure, particularly in thermosetting plastic matrices, which are not suitable for transmitting torsional loads effectively.
Innovation Solution
A thermoplastic polymer matrix composite torque shaft with end fittings connected via mutually complementarily shaped plug and socket connections that are interference fitted, allowing for deformation without machining and maintaining structural integrity, using circular braided reinforcing fabrics and thermoplastic deformable regions to enhance torsional load transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If metallic end fittings are used to connect to thermosetting composite tubes, then load transmission capability is improved, but slip and stress concentration failures occur leading to reduced reliability
Solution Approach 1:
The invention changes the material parameter from thermosetting to thermoplastic matrix, enabling the tube end to be deformed and formed into complementary plug and socket connections that interference-fit with the fitting, eliminating slip and stress concentration while maintaining load transmission capability
Solution Approach 2:
The invention uses a composite structure combining the thermoplastic matrix tube with deformable regions that can be shaped to create mechanical interlocking connections, integrating the benefits of composite material strength with deformable connection capability
2Ease of manufacture
If thermosetting plastic matrices are used in composite torque shafts, then manufacturing is simplified, but torsional load transmission is ineffective due to slip and stress concentration
Solution Approach 1:
The invention changes the matrix material from thermosetting to thermoplastic, which allows the tube end to be deformed and formed into complementary plug and socket connections that interference-fit with the fitting, eliminating slip and stress concentration while maintaining load transmission capability
Solution Approach 2:
The deformable region is prepared in advance during tube formation, allowing subsequent deformation into the required plug or socket shape to create the interference fit connection before final assembly
3Ease of manufacture
If traditional connection methods are used between end fittings and composite tubes, then manufacturing is easier, but structural integrity is compromised due to stress concentration at the interface
Solution Approach 1:
The invention changes the tube end geometry through deformation into complementary plug and socket shapes that create interference fits, distributing stress evenly across the connection interface and eliminating stress concentration points while maintaining manufacturing feasibility
Solution Approach 2:
The deformation process creates smooth curved surfaces in the plug and socket connections, avoiding sharp corners and edges that would cause stress concentration, thereby maintaining structural integrity
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 prevents slip and stress concentration failures, enabling efficient torsional load transmission throughout the length of the shaft while maintaining the structural integrity of the composite tube, making it interchangeable with metal torque tubes and reducing manufacturing complexity.
Implementation Method 1
the tube and end fittings are connected by mutually complementarily shaped plug and socket connections that are interference fitted by thermoplastically and/or mechanically deforming the ends of the tube into contact with the end fittings
Implementation Method 2
circular braided reinforcing fabrics embedded in a thermoplastic matrix which forms a tube
Data Source
Figure 1~3
Figure 4~8
Figure 9~11
AI summary
A torque shaft (20) comprising a hollow tube (22) provided with an end fitting (24, 26) at each end of a tube is made of a thermoplastic polymer matrix with reinforcing fibres embedded in the matrix, The tube (22) and end fittings (24, 26) are connected by mutually complementally shaped plugs (23) and sockets (27) that are dimensioned and positioned relative to each other to form an interference fit between the tube (22) and said plug (23) or socket (27).