Composite-to-Metal Interlock for Gas Turbine Joints
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Solution Overview
Problem
Existing methods for attaching composite components, such as airfoils, to metallic components in gas turbine engines face challenges due to high loads and limited size, with adhesive bonds being prone to dislodgment and mechanically fastened joints weakening the composite structure.
Innovation Solution
A composite article and method involving a composite component and a pre-threaded metallic component with interlock components woven through openings in the metallic component, which are co-cured to form an interlocking system, enhancing the bond strength between composite and metallic materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If adhesive bonds are used to join composite components to metallic components, then the joint is simple to manufacture, but the joint is prone to dislodgment under high loads
Solution Approach 1:
The joining system is segmented into multiple functional elements: adhesive bonds for basic attachment, mechanical fasteners for load-bearing connection, and composite reinforcement structures for structural integration. This segmentation allows each element to address specific aspects of the joining problem, with the adhesive providing seal and basic bonding, fasteners providing mechanical strength, and composite reinforcement distributing loads to prevent dislodgment.
2Strength
If mechanically fastened joints are used to join composite components to metallic components, then the joint strength is improved, but the composite structure is weakened due to fiber cutting
Solution Approach 1:
The composite structure is designed with local quality variations: the base composite material maintains its continuous fiber structure for overall strength, while localized reinforcement elements (such as composite sleeves or wrapped layers around fasteners) provide additional strength precisely at the fastener locations. This allows mechanical fasteners to be used for high joint strength without compromising the overall composite structure, as the reinforcement is concentrated only where needed to accommodate the fasteners.
Solution Approach 2:
The solution employs composite materials at the joint interface, such as composite reinforcement layers or hybrid composite-metallic fasteners. These composite materials bridge the gap between the composite airfoil and metallic mounting structure, distributing fastener loads across a larger area and preventing stress concentrations that would otherwise cut through the composite fibers and weaken the structure.
3Reliability
If composite reinforcement is added at the joint to prevent weakening, then the joint reliability is improved, but the weight benefit of composite materials is reduced
Solution Approach 1:
Composite reinforcement is applied locally only at the joint regions where mechanical fasteners are installed, rather than throughout the entire component. This localized reinforcement provides the necessary structural support to accommodate fasteners and distribute loads, while the majority of the component maintains its lightweight composite construction. The reinforcement is concentrated precisely where needed to prevent fiber cutting and maintain integrity, minimizing the additional weight.
Data Source
AI summary
A composite article including a composite component, a metallic component and one or more interlock components. The composite component including a plurality of composite plies and extending heightwise from a component base to a component tip and lengthwise between spaced apart component first and second edges, the composite. The metallic component including a first surface and a second surface and a plurality of openings formed therein extending from the first surface to the second surface. The metallic component including at least a portion substantially or fully embedded in the composite component. The one or more interlock components is interwoven through one or more of the plurality of openings in the metallic component and extending into and at least partially embedded in the composite component to provide an interlocking system between the composite component and the metallic component. A method of fabrication of a composite article is also provided.