Composite Containment Hook for Turbofan Fan Case
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Solution Overview
Problem
Turbofan engine cases face challenges in containing fan blades during a 'fan blade off' event, particularly in preventing damage to the wing or fuselage, while existing solutions either fail to reduce weight or compromise safety due to the use of metal materials.
Innovation Solution
A composite fan blade containment apparatus featuring a containment hook made of continuous carbon fiber or glass epoxy, bonded to the fan case barrel at both forward and aft locations, which shortens the axial length of the fan case and fan track liner, and includes a c-channel, tee, shelf, or candy cane shape to trap and manage the fan blade's motion effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal hardwall case with integral hook is used, then fan blade containment is achieved, but weight reduction is prevented
Solution Approach 1:
The patent replaces traditional metal hardwall case materials with composite materials that have high strength-to-weight ratios. The composite containment hook is bonded to a composite fan case barrel, achieving both weight reduction and maintained containment capability through the superior specific strength of composite materials.
Solution Approach 2:
The containment hook is manufactured as a separate component and bonded to the fan case barrel, rather than being an integral machined feature. This segmentation allows for optimized design of each component and simplifies manufacturing while maintaining structural integrity for fan blade containment.
2Reliability
If the fan case is elongated to include debris fence, then fan blade containment is improved, but additional material and weight are required
Solution Approach 1:
The patent uses composite materials for the containment hook and fan case barrel, leveraging their high strength-to-weight ratios to achieve effective containment without the weight penalty of elongated metal structures. The composite debris fence also utilizes composite materials to reduce weight while maintaining containment function.
Solution Approach 2:
Instead of elongating the fan case axially to provide containment, the patent uses a hook structure that provides containment through a different geometric configuration. The hook's curved geometry provides the necessary containment path without requiring additional axial length, thereby reducing material requirements and weight.
3Weight of stationary object
If composite materials are used for fan case, then weight reduction is achieved, but fan blade containment capability is compromised
Solution Approach 1:
The patent employs composite materials with high strength-to-weight ratios, such as carbon fiber reinforced polymers, to construct both the fan case barrel and containment hook. These composite materials provide sufficient mechanical strength to contain fan blades during failure events while achieving significant weight reduction compared to metal alternatives.
Solution Approach 2:
The containment hook features a curved, hook-shaped geometry that is optimized to contain fan blades. The curved profile of the hook, combined with the high specific strength of composite materials, provides effective containment capability while minimizing material usage and weight.
4Ease of manufacture
If integral metal hook is machined into metal fan case barrel, then manufacturing is simplified, but weight reduction and composite material benefits are lost
Solution Approach 1:
The containment hook is manufactured as a separate component from the fan case barrel and then bonded to it. This segmentation enables the use of composite materials for both components, achieving weight reduction while the bonding process maintains structural integrity. The separate manufacturing of the hook allows for optimized composite layup and curing processes.
Solution Approach 2:
A bonding agent or adhesive serves as an intermediary between the containment hook and fan case barrel, joining the two composite components together. This bonding interface transfers loads effectively between components while allowing each to be manufactured separately using composite material processes, achieving both weight reduction and manufacturing feasibility.
Data Source
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Figure 3A~4
AI summary
According to one aspect, a fan blade containment apparatus for turbofan engines includes a containment hook and a fan case barrel. The containment hook and the fan case barrel are formed from composite materials, and the containment hook is attached to the fan case barrel such that the containment hook contains forward motion of a fan blade during a fan blade off event. The apparatus further includes the containment hook being arranged to shorten the axial length of the fan case barrel.