Ceramic Matrix Composite Airfoil Repair With Interlocking Core Joint
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Solution Overview
Problem
Conventional methods for repairing composite airfoils in gas turbine engines, particularly at thin sections, result in distorted parts and joints that are vulnerable to tensile and shear loads, leading to faster wear and deterioration, requiring frequent repairs.
Innovation Solution
A method involving machining an interlocking feature into the airfoil, joining a replacement core with complementary interlocking features, and overlaying the joint with plies to provide structural integrity and alignment, while bonding the components to enhance mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If conventional repair methods (attaching new plies or brazing) are used on thin-section airfoils, then the repair can be performed, but the repaired airfoil becomes distorted and the joint is vulnerable to tensile and shear loads
Solution Approach 1:
The repair method segments the airfoil structure by introducing a replacement core that is inserted into a cavity within the airfoil. This core acts as a separate structural element that can be independently manufactured and fitted, allowing the thin airfoil section to be reinforced without distorting the original structure. The core divides the load path, protecting the joint from direct tensile and shear stresses.
Solution Approach 2:
The replacement core serves as an intermediary element between the damaged airfoil structure and the repair plies. Instead of directly attaching plies to the thin airfoil surface (which causes distortion), the core provides a substantial substrate for ply attachment. The core transfers and distributes loads, mediating the stress between the plies and the airfoil structure.
2Strength
If brazing is used to join replacement material to the airfoil, then bonding is achieved, but the brazed joint is particularly vulnerable to tensile and shear loads and the mechanical properties of the airfoil are affected
Solution Approach 1:
The method replaces the brazing process (thermal/mechanical joining) with a mechanical insertion system. The replacement core is machined with interlocking features that physically engage with corresponding features in the airfoil cavity. This mechanical interlocking system substitutes for the brazed joint, providing superior resistance to tensile and shear loads without the thermal effects of brazing that can degrade the airfoil material properties.
Solution Approach 2:
The repair utilizes composite material construction where the replacement core (made of composite material) is overlaid with composite plies. This creates a composite-reinforced structure where the core provides structural integrity and the plies provide surface restoration and additional strength. The composite-on-composite interface is bonded using compatible resin systems, creating a durable joint that maintains the airfoil's mechanical properties.
3Ease of manufacture
If new plies are attached to damaged areas of thin airfoil sections, then the damaged area is covered, but the thin sections offer little structure for the new plies to attach and align with
Solution Approach 1:
The replacement core is pre-manufactured with precise interlocking features before insertion into the airfoil. The core's geometry, including its interlocking tabs and slots, is precisely machined to ensure proper alignment with the airfoil cavity. This preliminary precision manufacturing of the core eliminates the need to achieve precise alignment during the repair assembly process, as the core itself provides the alignment references.
Solution Approach 2:
The replacement core acts as an intermediary that provides a substantial, precisely-formed substrate for attaching the repair plies. The core's larger cross-section compared to the thin airfoil surface provides adequate structure for ply attachment and alignment. The plies attach to the core rather than directly to the thin airfoil, ensuring proper alignment and distribution of stresses.
Data Source
AI summary
Methods for repairing composite components are provided. For instance, one exemplary method includes machining an interlocking feature into an existing component. A replacement material or core having an interlocking feature complementary to the interlocking feature of the existing component is then joined with the component. The interlocking features interlock to form a joint. The joint is then overlaid with one or more plies to rebuild the outer surface of the component and seal the joint. A bonding process can be used to chemically bond the newly joined parts together. Repaired composite components are also provided.