Composite Airfoil Metal Patch Dovetail Stress Reduction
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Solution Overview
Problem
Gas turbine engine airfoils face stress concentration and fatigue issues due to extreme mechanical and thermal loading, limiting their durability and life, especially at the dovetail and shank regions.
Innovation Solution
A composite airfoil with a metal patch is introduced, which can be bonded to the dovetail and shank, optionally with a shim and wear strip, to redistribute loads and reduce stress concentrations, using materials like titanium alloys and varying thickness configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If composite materials are used to reduce weight of airfoil components, then weight reduction is achieved, but stress concentration and fatigue life are worsened at the dovetail and shank regions
Solution Approach 1:
The patent applies composite materials by bonding a metal patch (such as titanium alloy) to the composite airfoil at the dovetail and shank regions. This creates a hybrid structure where the metal patch provides superior mechanical properties and stress distribution, while the composite airfoil maintains weight reduction benefits. The metal patch acts as a reinforcement layer that interfaces with the composite material through adhesive bonding, effectively combining the advantages of both material systems.
Solution Approach 2:
The patent implements local quality by applying the metal patch specifically at the dovetail and shank regions where stress concentrations occur, rather than reinforcing the entire airfoil. This localized reinforcement targets the critical areas that experience highest mechanical and thermal loading, improving fatigue life where it is most needed while minimizing additional weight.
2Reliability
If metal patch is added to composite airfoil to improve fatigue life, then reliability is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies segmentation by dividing the airfoil into distinct functional zones: the composite airfoil body for weight reduction, and the metal patch at the dovetail and shank for stress management. This segmentation allows each component to be optimized independently and assembled through bonding, simplifying the overall manufacturing process compared to creating a monolithic structure.
Solution Approach 2:
The patent uses an adhesive layer as an intermediary between the metal patch and the composite airfoil. This intermediary enables the bonding of dissimilar materials (metal to composite) and facilitates stress transfer between the two materials, resolving the complexity of directly joining incompatible materials while maintaining structural integrity.
3Stress or pressure
If metal patch is used to redistribute loads, then stress concentration is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-positioning the metal patch at the dovetail and shank regions before final assembly. The patch is bonded to the composite airfoil in a controlled manufacturing environment, allowing for precise alignment and positioning. This preliminary placement ensures optimal stress distribution patterns are achieved before the airfoil enters service.
Data Source
AI summary
A composite airfoil comprises a leading edge and a trailing edge, a pressure side and a suction side extending between the leading edge and the trailing edge, a tip at a radial outer end of the airfoil, a shank at a radial inner end of the airfoil, a dovetail connected to the shank, and a metal patch disposed between the dovetail and the shank.