Composite Transmission Shaft Coupling With Spline-Filling Mandrel
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Solution Overview
Problem
Existing methods for manufacturing transmission shafts with composite bodies and metallic coupling parts often result in interstices and porosities, leading to reduced mechanical strength, sensitivity to environmental conditions, and fatigue issues due to debris generation and differential stress absorption.
Innovation Solution
A method involving filament winding of pre-impregnated fibers around a mandrel with an expandable and non-expandable part, where the coupling part is positioned around the body and the mandrel is expanded to fill splines and grooves with fibers, eliminating the need for adhesives and reinforcements, and ensuring precise control over dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the tube is degraded to secure the coupling part to the body of the shaft, then the coupling part can be attached to the composite tube, but cracks are initiated which will spread in use and interstices and porosities are formed that reduce mechanical strength
Solution Approach 1:
The spline profiles are pre-formed on the mandrel before the composite tube is wound. This preliminary action ensures that when the tube is subsequently wound and cured, the fibers are already positioned to interlock with the splines, eliminating the need for post-manufacturing degradation and preventing crack initiation.
Solution Approach 2:
Instead of degrading the tube after it is manufactured to create attachment features, the invention inverts the approach by pre-forming the spline profiles on the mandrel before the tube is wound. The attachment features are created during the manufacturing process itself, not after, thereby avoiding damage to the tube structure.
2Manufacturing precision
If an inflatable element is used to expand the tube during manufacturing, then the tube can be expanded to fit the coupling part, but precise control of the internal diameter is difficult and tooling costs increase
Solution Approach 1:
The invention replaces the complex inflatable element system with a simple mechanical mandrel. The mandrel's rigid structure and precise geometry provide inherent control over the tube's internal diameter without requiring complex inflation mechanisms, pressure control systems, or expensive mold tooling.
Solution Approach 2:
The mandrel serves as an intermediary tool that defines the internal geometry of the tube during manufacturing. By using a pre-formed mandrel with spline profiles instead of an inflatable element, the system achieves precise dimensional control through a simple, reusable tool that does not require complex control mechanisms.
3Strength
If the tube is degraded to form mechanical connection with the coupling part, then the coupling can be secured to the body, but debris is generated that creates interstices and porosities detrimental to mechanical strength
Solution Approach 1:
The spline profiles are pre-formed on the mandrel before the composite tube is wound. This preliminary action ensures that when the tube is subsequently wound and cured, the fibers are already positioned to interlock with the splines, eliminating the need for post-manufacturing degradation and preventing crack initiation.
Solution Approach 2:
The invention converts the potential harm of fiber disruption into a benefit by deliberately designing the spline profiles to work with the fiber orientation. The splines are formed in a way that guides and utilizes the pre-impregnated fibers to create interlocking mechanical keys, transforming what could be fiber damage into a strengthening interlock mechanism.
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 method achieves a homogeneous structure with perfect contact between the coupling and the shaft body, enhancing mechanical properties, reducing porosity, and allowing precise dimension control, thus improving the shaft's resistance to fatigue and environmental factors while minimizing tooling costs.
Implementation Method 1
The mandrel (10) comprises an expandable part (12) and a non-expandable part (11). The coupling part (3) is positioned around the body (2) at the level of the expandable part (12) of the mandrel (10). The expandable part (12) of the mandrel (10) is expanded to fill the bottom of the splines with the pre-impregnated fibers of the body (2).
Implementation Method 2
production of the body by filament winding of pre-impregnated fibers around the mandrel
Implementation Method 3
The expandable part (12) of the mandrel (10) is expanded to fill the bottom of the splines with the pre-impregnated fibers of the body (2)
Data Source
Figure 1~2
Figure 3~4
Figure 5~7
AI summary
The invention relates to a method for producing a transmission shaft (1) comprising a body (2) made from composite and a coupling piece (3) at one end of the body (2), said coupling piece (3) being hollow and having splines (4) on the inner surface thereof, the base (6) of the splines (4) delimiting the perimeter of a circle of diameter D2 and the head (5) of the splines (4) delimiting the perimeter of a circle of diameter D1, characterized in that said method comprises the successive steps of: - providing a mandrel (10) having an expandable part (12) and a non-expandable part (11); - producing the body (2) by winding pre-impregnated fibre filaments around the mandrel (10); - positioning the coupling piece (3) around the body (2) on the expandable part (12) of the mandrel; - expansion of the expandable part (12) of the mandrel (10) in order to fill the base (6) of the splines (4) with the impregnated fibres of the body (2); - curing the body (2) provided with the coupling piece (3).