Composite Airfoil Spar Tab Mechanical Lock
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Solution Overview
Problem
Existing methods for attaching composite airfoils to metallic attachments in gas turbine engines face challenges due to dislodging forces and moments, leading to reduced durability and lifespan of both the airfoils and fan frame assemblies.
Innovation Solution
A composite airfoil design featuring a spar with an embedded tab that includes a surface pattern matching the ply surface pattern, providing a mechanical lock when molded and cured, which enhances the attachment to a metallic shank, resisting dislodging forces and moments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If simple adhesive bonds are used to attach composite airfoils to metallic attachments, then the attachment process is simple, but the bonds are subject to forces and moments that tend to dislodge the composite airfoils, reducing reliability and durability
Solution Approach 1:
The attachment interface is segmented into multiple interaction points through the surface pattern featuring protrusions and recesses. This segmentation distributes the mechanical loads across multiple contact points rather than relying on a single adhesive bond, thereby improving resistance to dislodging forces and moments while maintaining manufacturing feasibility.
Solution Approach 2:
The invention uses a composite attachment system combining metallic components with composite surface patterns. The metallic attachment provides structural strength while the composite surface pattern (protrusions and recesses) interfaces with the composite airfoil plies, creating a hybrid system that leverages the advantages of both material types to resist dislodging forces.
2Weight of moving object
If composite airfoils are mounted to metallic attachments, then weight reduction is achieved, but the magnitude of loads and limited size of components make the attachment challenging
Solution Approach 1:
The surface pattern is applied locally at the attachment interface rather than throughout the entire airfoil structure. This local modification provides the necessary mechanical interlocking capability exactly where loads are transmitted, without adding unnecessary complexity or weight to the rest of the lightweight composite airfoil structure.
Solution Approach 2:
The attachment solution moves from a two-dimensional adhesive bond to a three-dimensional mechanical interlock using protrusions and recesses. This dimensional transition creates additional load-bearing pathways through the attachment interface, enabling the lightweight composite airfoil to withstand higher loads without increasing overall structural complexity.
3Ease of manufacture
If an integral composite/metallic system is desired, then complex machining of metallic interface is utilized, but joining the two systems has been challenging due to dislodging forces
Solution Approach 1:
The surface pattern (protrusions and recesses) is pre-formed on the metallic attachment before the composite airfoil is bonded to it. This preliminary action creates a mechanical interlocking framework that is already in place to resist dislodging forces, eliminating the need for complex post-attachment reinforcement while maintaining manufacturing efficiency.
Data Source
AI summary
A composite article including composite component mounted on a spar including a shank extending heightwise from below component base up into composite component. Tab at an upper end of shank substantially or fully embedded in the composite component and at least one ply surface pattern of the composite component contacting and generally conforming to at least one spar surface pattern on the tab.Spar surface pattern may include spaced apart spar surface protrusions with spar surface spaces therebetween and spar surface protrusions extending outwardly from spar and disposed between tows in ply surface pattern. Tows may be layed up in spar surface spaces. Spar surface pattern may include continuous or segmented spaced spar surface protrusions and spar surface spaces therebetween with tows in ply surface pattern disposed in spar surface spaces. The composite article may be a composite blade or vane including a composite airfoil.