Composite Turbomachine Blade Root with Metal Plate Clamping
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Solution Overview
Problem
The production of composite material turbomachine blades with bulbous roots is complicated and costly due to material losses, delicate manipulations, and high mechanical property requirements, with existing solutions risking damage from concentrated centrifugal forces.
Innovation Solution
A rotor disc blade with a composite material root sandwiched between two metal plates fixed by a screw and nut, ensuring non-slip contact and distributing centrifugal forces across the surface, with features like conical heads, chamfers, and structured surfaces to enhance friction and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If an insert is used to form the bulbous root in composite material blades, then the root geometry can be obtained, but the manufacturing process becomes complicated and costly with significant material losses
Solution Approach 1:
The blade is divided into two parts: a simple planar root portion made of composite material and separate metal plates that form the bulbous geometry. This segmentation allows the complex shaping function to be transferred from the composite material to the metal plates, which are easier to manufacture and assemble.
Solution Approach 2:
Metal plates are introduced as intermediary elements between the planar composite root and the final bulbous geometry. These plates serve as mediators that provide the complex shape while being attached to the simpler composite structure, avoiding the need to directly form the complex geometry in the composite material itself.
2Shape
If metal plates are held by a welded stud, then the root geometry is obtained, but centrifugal forces concentrate at the composite material contact zone causing damage risk
Solution Approach 1:
The force transmission path is segmented: the welded stud provides only positioning, while the metal plates bear the centrifugal loads. This separates the positioning function from the load-bearing function, preventing stress concentration at a single composite-material contact point.
Solution Approach 2:
The metal plates act as intermediaries that distribute centrifugal forces across a larger area of the composite root. Instead of concentrating forces at the stud-composite interface, the plates spread the loads over the entire contact surface between the plates and the composite material.
3Ease of manufacture
If the blade root is made as a single composite piece, then manufacturing is simpler, but the bulbous geometry and force absorption are difficult to achieve
Solution Approach 1:
The blade is segmented into a simple planar root portion (easy to manufacture as single-piece composite) and separate metal plates (providing the bulbous geometry). This allows each component to be optimized for its specific manufacturing requirements while achieving the final complex geometry through assembly.
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 design allows for reliable and reproducible absorption of centrifugal forces, reducing stress concentration and tilting risks, while maintaining clamping force over temperature ranges, thus enhancing the durability and efficiency of composite material blades.
Implementation Method 1
the screw and the nut applying to the metal plates a minimum clamping force capable of ensuring absorption, by friction between the metal plates and the lateral flanks of the blade root, of a determined centrifugal force applied to the blade
Implementation Method 2
The face of each plate facing the blade root has a structured surface so as to increase the friction between the plates and the blade root
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A rotor disc blade (10) for a turbomachine made from composite material comprising a fibrous reinforcement obtained by multilayer weaving of yarns and densified by a matrix. The blade (10) comprises a portion that forms the airfoil (12) and the blade root (14) forming a single part, the blade root (14) having two substantially planar opposing side flanks (22, 24) that are formed in the respective extensions of the pressure (12a) and suction (12b) surfaces of the airfoil (10). The blade root (14) is gripped between two metal plates (26, 28) fixed against the side flanks (22, 24) of the blade root by a screw (30) and a nut (40) passing through the plates (26, 28) and the blade root (14). The screw (30) comprises a head (31) bearing on one (26) of the two plates. The nut (40) comprises a head (41) bearing on the other plate (28). The screw and the nut (30, 40) apply, to the metal plates (26, 28), a minimum clamping force capable of taking up, by friction between the metal plates (26, 28) and the side flanks (22, 24) of the blade root (14), a predefined centrifugal force applied to the blade (10).