Composite Fan Casing With Annular Stiffener for Lower Weight
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Solution Overview
Problem
Current aircraft turbomachine blower housings are heavy and complex due to the use of solid abradable support cartridges and metallic stiffeners, which increase weight and cost, and are prone to dynamic stress-induced deterioration.
Innovation Solution
A blower housing made of composite material with an omega-shaped annular stiffener inside, providing reinforcement while maintaining a reduced mass and improved retention capacity, using a preform of woven fibers densified by a polymer resin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid abradable support cartridge is used in the blower housing, then the abradable material can be retained and installed, but the weight of the blower housing increases
Solution Approach 1:
The patent employs a honeycomb-structured abradable support cartridge instead of a solid cartridge. The honeycomb structure provides sufficient mechanical strength and retention capacity while significantly reducing the weight compared to a solid structure. The cellular geometry distributes loads effectively across the structure, maintaining integrity while minimizing mass.
Solution Approach 2:
The abradable support cartridge is constructed using composite materials that combine structural integrity with weight reduction. The honeycomb structure typically uses lightweight materials such as aluminum or composite cores with appropriate surface treatments, creating a composite structure that optimizes both strength-to-weight ratio and abradable material retention.
2Strength
If metallic stiffeners are added to reinforce the blower housing, then the mechanical strength increases, but the weight and manufacturing complexity increase
Solution Approach 1:
Instead of uniformly reinforcing the entire blower housing with metallic stiffeners, the patent applies reinforcement locally where needed. The honeycomb structure provides localized stiffness and strength at critical areas, eliminating the need for extensive metallic stiffener networks. This approach maintains mechanical strength while minimizing added weight and complexity.
Solution Approach 2:
The blower housing utilizes composite material construction that inherently provides high strength-to-weight ratio, reducing or eliminating the need for additional metallic stiffeners. The composite structure can be engineered with varying fiber orientations and densities to provide strength exactly where required, without the weight penalty of traditional metallic reinforcement.
3Strength
If metallic stiffeners are integrated into the blower housing, then the structural reinforcement is achieved, but the manufacturing complexity and cost increase
Solution Approach 1:
The blower housing is designed as a modular assembly where the honeycomb abradable support cartridge is a separate, pre-fabricated component that can be independently manufactured and then installed. This segmentation allows each component to be optimized and manufactured separately using appropriate processes, reducing overall manufacturing complexity compared to integrating stiffeners into a monolithic structure.
Solution Approach 2:
The honeycomb structure can be manufactured using cost-effective processes such as extrusion, molding, or bonding of cellular cores, which are well-established industrial techniques. This approach is simpler and more economical than integrating complex metallic stiffener networks into the housing structure, particularly when using lightweight composite materials that can be formed into the required shapes.
Data Source
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AI summary
The invention concerns a fan casing (10) for an aircraft turbomachine, comprising an annular body (11) extending around an axis and equipped with an annular attachment flange (12a, 12b) at each of its axial ends, and an annular coating (14) made from abradable material, characterised in that the body (11) is made from a composite material, and in that it further comprises an annular stiffener (13) that is arranged inside the body (11) and that carries the coating (14), this stiffener (13) comprising an annular ring (13a), a radially outer face of which is separated radially from the body (11) and a radially inner face of which receives the coating (14), the stiffener (13) comprising annular attachment tabs (13b) for attaching the wall to the body.