Composite Shaft Tapered Joint for Even Preload Distribution
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Solution Overview
Problem
Existing composite structural components face challenges in forming robust and weight-efficient end connections with metallic components, particularly in aerospace applications, where complex geometry and uneven contact pressure distribution lead to joint failure and increased weight due to the use of metal end fittings with flat lands for frictional engagement.
Innovation Solution
A composite shaft with a tapered interface surface and a preload structure that applies varying contact pressure along its length, ensuring even force distribution across the joint by shaping the shaft and preload structure to compensate for the tapered interface, thereby reducing weight and enhancing joint strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flat lands are provided in the tooth profile for frictional engagement, then wear properties of the connection are improved, but the length of the end fitting increases significantly resulting in increased weight
Solution Approach 1:
The invention extracts and eliminates the flat lands portion from the tooth profile, retaining only the essential cutting teeth for force transmission. This removes the source of excessive friction during assembly while maintaining adequate wear properties through the remaining tooth engagement geometry.
Solution Approach 2:
The invention changes the tooth profile parameters by reducing or eliminating the flat land portion, thereby altering the friction characteristics and contact geometry. This parameter modification allows for reduced end fitting length and weight while maintaining functional performance.
2Reliability
If high assembly-torque is applied to provide frictional engagement, then preload on the joint is improved preventing fretting, but additional layers of composite are required to combat assembly loads increasing size and weight
Solution Approach 1:
The invention removes the flat lands that generate excessive friction during assembly, thereby eliminating the need for high assembly-torque. This extraction of the friction-generating feature prevents the need for additional composite layers to withstand assembly loads.
Solution Approach 2:
By changing the tooth profile to minimize frictional contact during assembly, the invention alters the assembly load parameters. This allows the composite shaft to be designed for operational loads only, without requiring excess material to withstand assembly forces.
3Weight of moving object
If metals are used for end connections with complex geometry, then weight efficiency and cost are improved, but joining challenges to composite structural components increase significantly
Solution Approach 1:
The invention uses composite materials for both the shaft and end fitting, creating material compatibility that simplifies the joining process. The composite end fitting can be integrated with the composite shaft through matched tooth profiles that minimize assembly friction and thermal mismatch, eliminating the complexities of metal-to-composite joining.
Solution Approach 2:
The invention changes the material parameters of the end fitting to match the composite shaft, thereby altering the thermal and mechanical compatibility. This material selection change simplifies the joining process by eliminating the disparate properties that complicate metal-to-composite assemblies.
4Ease of manufacture
If compressed air is used to remove contaminants from bearing surfaces, then cleaning effectiveness is improved, but moisture condensation on bearing surfaces occurs causing corrosion
Solution Approach 1:
The invention converts the harmful cold temperature of compressed air into a beneficial drying effect. By controlling the air pressure and exposure time, the cold air rapidly evaporates moisture from bearing surfaces while simultaneously removing contaminants, transforming a potential corrosion risk into an effective drying and cleaning process.
Solution Approach 2:
The invention changes the parameters of the compressed air system, specifically controlling pressure, flow rate, and exposure duration. By optimizing these parameters, the system achieves effective contaminant removal and moisture evaporation without causing condensation, transforming the cleaning process to avoid corrosion.
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 achieves a more even contact pressure distribution across the composite shaft and end fitting interface, increasing joint strength and reducing weight by allowing a smaller, lighter design while maintaining robust force transmission.
Implementation Method 1
a preload structure arranged to provide a biasing force to bias the composite shaft against the end fitting
Implementation Method 2
the shaft has a second interface surface for engagement with the first interface surface, the second interface surface being tapered at an angle to the shaft axis
Data Source
AI summary
A composite shaft with an end fitting mounted on one end of said shaft and a preload structure arranged to provide a biasing force to bias the composite shaft against the end fitting. The end fitting has a first interface surface, the first interface surface being tapered at an angle to the shaft axis and the shaft has a second interface surface for engagement with the first interface surface and is tapered at an angle to the shaft axis, the second interface surface extending axially from a first end to a second end, the shaft being thicker at the second end than at the first end. The shaft has a third interface surface and the preload structure has a fourth interface surface and the contact pressure of the third interface against the fourth interface increases from the first end of the shaft to the second end of the shaft.