Ceramic Matrix Composite Joint for Turbine Shroud
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Solution Overview
Problem
The challenge lies in manufacturing load-bearing ceramic matrix composite (CMC) components, such as turbine nozzle bands, with complex geometries, where fiber orientation is critical for strength and toughness, but existing methods face difficulties in achieving desired fiber orientations without bending fibers around tight corners, leading to manufacturability challenges and potential brittle failures in interlocking mechanical joints.
Innovation Solution
The use of interlocking mechanical joints, specifically designed to orient reinforcing fibers normal to the load direction, which are formed during the CMC processing stages, allowing for the integration of subcomponents with simple geometry to create damage-tolerant and tough structures, reducing the likelihood of brittle failures by distributing loads and minimizing interlaminar damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If fibers are bent around tight corners to achieve complex geometries, then the component can be manufactured with complex shapes, but the fiber orientation deviates from the load direction reducing strength and increasing brittleness
Solution Approach 1:
The CMC component is divided into multiple subcomponents with simpler geometries that can be manufactured separately with optimal fiber orientations. These subcomponents are then joined together using mechanical joints to form the final complex-shaped component, avoiding the need to bend fibers around tight corners while maintaining strength.
Solution Approach 2:
Mechanical joints are embedded within the CMC structure during manufacturing, creating nested features that allow subcomponents to interlock. These joints provide load path continuity and maintain fiber orientation alignment in each subcomponent while achieving the overall complex geometry of the assembled component.
2Stability of the object's composition
If CMC components are manufactured as single integrated pieces, then fiber continuity is maintained, but manufacturing complexity and difficulty increase significantly
Solution Approach 1:
The component is segmented into multiple subcomponents that are manufactured separately using standard CMC fabrication processes. This reduces the manufacturing complexity of each individual piece while maintaining fiber continuity within each subcomponent. The subcomponents are then joined using mechanical joints that preserve the overall structural integrity.
Solution Approach 2:
Mechanical joints serve as intermediary elements between subcomponents, providing a controlled interface that maintains load path continuity. These joints are designed to work with the CMC material properties and are integrated during the manufacturing process, allowing separate fabrication of subcomponents while achieving integrated component performance.
3Ease of manufacture
If mechanical joints are used to join CMC subcomponents, then manufacturing complexity is reduced, but the joints become potential failure points due to interlaminar damage
Solution Approach 1:
The mechanical joints are designed with localized fiber reinforcement and optimized geometry to distribute loads away from potential interlaminar damage zones. The joint regions incorporate specific fiber orientations and stacking sequences that enhance toughness and prevent delamination, making these locations more reliable rather than weaker points.
Solution Approach 2:
The mechanical joint design incorporates features that prevent interlaminar damage before it can occur. This includes rounded transitions, adequate fillet radii, and progressive load transfer mechanisms that cushion stress concentrations and prevent crack initiation at the joint interfaces during manufacturing and service.
Data Source
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AI summary
A ceramic matrix composite (CMC) component including a subcomponent, such as a band flowpath (64), a load bearing wall (68) and a wall support (68, 72, 86), each comprised of a ceramic matrix composite (CMC) including reinforcing fibers (84) embedded in a matrix. The CMC component further including at least one mechanical joint joining the subcomponent, the load bearing wall (68) and the wall support (68, 72, 86) to form the CMC component. The reinforcing fibers (84) of the load bearing wall (68) are oriented substantially normal to the reinforcing fibers (84) of the subcomponent and the wall support (68, 72, 86). Methods are also provided for joining the subcomponent, the load bearing wall (68) and the wall support (68, 72, 86) to form a mechanical joint.