CMC Component Edge Crack Resistance via Perpendicular End Cap Plies
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Solution Overview
Problem
Ceramic matrix composite (CMC) components laminated from unidirectional prepreg tape are prone to edge cracks due to in-plane tensile stress, which limits their useful life in high-temperature applications such as gas turbine engines.
Innovation Solution
The addition of end cap plies oriented perpendicular to the laminate plane, which cover the exposed edges and provide bridging fibers to resist translaminar matrix cracks, significantly enhancing the resistance to edge cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If CMC components are laminated from unidirectional prepreg tape, then the component can be manufactured with high temperature capability and light weight, but the component becomes prone to edge cracks under in-plane tensile stress
Solution Approach 1:
The invention introduces end cap plies as a separate structural element that segments the laminate structure. These end cap plies are positioned at the edges of the laminate and oriented perpendicular to the main laminate plane, creating a segmented architecture that specifically addresses edge crack susceptibility while preserving the high-temperature performance of the base CMC structure
Solution Approach 2:
The invention adds a third dimension to the laminate structure by incorporating end cap plies that extend perpendicular to the main laminate plane. This dimensional addition creates bridging fibers that span across potential crack paths in the edge region, providing crack resistance without compromising the high-temperature capability of the original CMC laminate
2Reliability
If end cap plies are added to cover exposed edges, then resistance to edge cracks is doubled, but the device complexity increases
Solution Approach 1:
The end cap plies are applied locally only at the exposed edges of the laminate structure, rather than throughout the entire component. This localized application provides targeted crack resistance at the vulnerable edge regions while minimizing the overall structural complexity and material usage
Solution Approach 2:
The invention creates a composite laminate structure by combining the base CMC plies with additional end cap plies that have different fiber orientations. This composite architecture integrates materials with complementary properties - the base plies provide high-temperature capability while the end cap plies provide edge crack resistance, achieving enhanced reliability without excessive complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The incorporation of end cap plies doubles the resistance to edge cracks and prolongs the useful life of CMC components by inhibiting crack propagation, even under high loading conditions.
Implementation Method 1
the fibers in the end cap ply are configured to bridge a translaminar matrix crack on or in the laminate structure
Implementation Method 2
compliance of the matrix between the fibers in the end cap ply is less than about 0.06 inch/inch
Data Source
AI summary
A ceramic matrix composite (CMC) component includes a plurality of CMC plies stacked together to form a laminate structure. First and second CMC plies of the laminate structure are formed from a CMC material reinforced with a fiber material and have first and second fiber orientations, respectively. The first and second fiber orientations are arranged in a cross-ply pattern in a plane of the laminate structure. The laminate structure includes at least one edge. The CMC component further includes at least one end cap ply covering at least a portion of the at least one edge of the laminate structure. The end cap ply is formed of the CMC material reinforced with the fiber material having a third fiber orientation. Further, at least a portion of a plane of the at least one end cap ply is perpendicular to the plane of the laminate structure.