CMC Component Interlocking Mechanical Joint Design
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Solution Overview
Problem
Current methods for joining ceramic matrix composite (CMC) subcomponents in gas turbine engines face challenges such as brittle bond lines and limited toughness, leading to potential catastrophic failures under applied loads, especially when the interlocking feature is oriented to fail in the interlaminar direction, which exploits the lower interlaminar properties of CMCs.
Innovation Solution
The use of interlocking mechanical joints with orthogonal fiber orientations and optional reinforcing CMC pins in joints like dado, rabbet, and dovetail configurations, which require fiber breakage to fail, thereby enhancing the toughness and damage tolerance of the joint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bonding methods (diffusion bonding, reaction forming, melt infiltration, brazing, adhesives) are used to join CMC subcomponents, then the components can be assembled into complete structures, but the bond lines are brittle and have limited toughness, leading to potential catastrophic failures under applied loads
Solution Approach 1:
The joint is segmented into multiple functional zones: an interlocking mechanical feature (dado, rabbet, or dovetail) that provides geometric interlock, and reinforcing CMC pins that provide tensile strength. This segmentation allows each element to contribute its strengths, avoiding the brittleness of conventional bonding while maintaining assembly capability.
Solution Approach 2:
The joint employs a composite structure combining the CMC subcomponents with reinforcing CMC pins inserted into the interlocking features. This composite approach creates a joint that leverages both the mechanical interlock of the geometric feature and the tensile strength of the pin, achieving superior toughness and reliability compared to conventional bonding methods.
2Ease of manufacture
If the interlocking feature is oriented to fail in the interlaminar direction, then assembly is simplified, but the lower interlaminar properties of CMCs are exploited, leading to joint failure
Solution Approach 1:
Reinforcing CMC pins are preliminarily inserted into the interlocking mechanical feature during assembly, before the component is subjected to service loads. This preliminary action ensures that the pins are in place to provide tensile strength and prevent interlaminar shear failure, while still allowing simplified assembly through the interlocking geometry.
Solution Approach 2:
The joint design changes the failure mode parameter from interlaminar shear (governed by weak properties) to pin tensile failure (governed by strong properties). By orienting the pin to resist tensile loads and the interlocking feature to prevent interlaminar shear, the design exploits the stronger tensile properties of CMC materials rather than the weaker interlaminar properties.
Data Source
AI summary
A ceramic matrix composite (CMC) component including a first subcomponent and a second subcomponent. The first component formed of a ceramic matrix composite (CMC) including reinforcing fibers embedded in a matrix and the second CMC subcomponent formed of one of a ceramic matrix composite (CMC) including reinforcing fibers embedded in a matrix or a monolithic ceramic material. The subcomponents further including an interlocking mechanical joint joining the first subcomponent and the second subcomponent to form the composite material component. The interlocking mechanical joint including at least one groove defined in one of the first subcomponent or the second subcomponent and into which a portion of the other of the first subcomponent or the second subcomponent is disposed. A shroud segment is provided formed of the joined first and second subcomponents. Methods are also provided for joining the first and second subcomponents using an interlocking mechanical joint.