Segmented Fan Case Backsheet for Crack Arrest
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Solution Overview
Problem
Turbine engine fan cases face challenges in containing fan blade fragments during a blade-out event, leading to potential rapid crack propagation and structural integrity issues, which can cause further damage and safety hazards.
Innovation Solution
A segmented backsheet structure with asymmetrical overlaps and a removable containment cartridge is introduced, where the backsheet structure is coupled to a honeycomb structure and the containment cartridge is axially retained with brackets, using materials like UHMWPE for efficient blade fragment retention and easy replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional fan case structure is used, then the structural integrity is maintained under normal conditions, but rapid crack propagation occurs during fan blade-out events
Solution Approach 1:
The backsheet is divided into multiple segments (first backsheet segment, second backsheet segment, third backsheet segment) that are coupled together with asymmetrical overlaps. This segmentation prevents rapid crack propagation by creating discontinuities in the structure, while the asymmetrical overlap design maintains overall structural integrity through distributed load paths.
Solution Approach 2:
The backsheet segments are coupled using asymmetrical overlaps where the first backsheet segment overlaps the second, the second overlaps the third, but with different overlap configurations. This asymmetry disrupts crack propagation paths while maintaining structural strength through varied load distribution across the segments.
2Reliability
If a fixed containment structure is used, then blade fragment retention is achieved, but maintenance and replacement are difficult
Solution Approach 1:
The containment cartridge is designed as a removable component that can be extracted from the fan case assembly. This allows the containment cartridge to be easily removed for maintenance and replacement without disassembling the entire fan case, while still providing effective blade fragment retention when installed.
Solution Approach 2:
The containment cartridge transitions from a fixed, permanent installation to a dynamic, removable component. This enables the containment system to adapt between its operational function of retaining blade fragments and its maintenance function of being easily replaced, improving both reliability and ease of repair.
3Reliability
If a segmented backsheet structure is introduced, then crack propagation is arrested, but device complexity increases
Solution Approach 1:
The backsheet is segmented into multiple sections coupled together with asymmetrical overlaps. This segmentation provides crack arrest capability by creating discontinuities that stop crack propagation, while the modular nature of the segments allows for standardized manufacturing and assembly, partially offsetting the increased structural complexity.
Data Source
AI summary
A fan case with crack-arresting backsheet structure and removable containment cartridge is disclosed. An example engine fan case includes a segmented backsheet structure, the segmented backsheet structure including at least a first backsheet segment of a first length and a second backsheet segment of a second length, the first backsheet segment coupled to the second backsheet segment and at least one of the first backsheet segment or the second backsheet segment coupled to the fan case, a honeycomb structure, and a containment structure for blade fragment retention, the containment structure coupled to the segmented backsheet structure.