Composite Fan Containment Case with Metallic Backing
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Solution Overview
Problem
Composite fan cases for gas turbine engines face challenges in accommodating bolt holes and achieving reliable tolerance ranges due to limitations in manufacturing techniques, making it difficult to attach components securely.
Innovation Solution
A composite fan containment case design featuring a metallic backing and integral mounting ring, with a bolt attachment system that includes a composite boss with metallic inserts and adhesive, allowing for secure attachment and containment of fan blades while maintaining a non-metallic, lightweight structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If composite materials are used to construct the fan case, then weight is reduced and containment capability is provided, but the material is not accommodating of bolt holes and manufacturing tolerances are limited
Solution Approach 1:
The fan case is divided into multiple composite layers that can be manufactured separately and then assembled together. This segmentation allows each layer to be manufactured with standard tolerances, and the cumulative assembly achieves the required precision for bolt hole locations while maintaining the lightweight composite construction.
Solution Approach 2:
A metallic backing plate is introduced as an intermediary component between the composite layers and the bolt attachment system. The metallic backing plate provides precise bolt hole locations and threading, while the composite layers provide the lightweight containment structure. This mediator resolves the contradiction by combining the advantages of both materials.
2Reliability
If metallic fan cases are used, then containment function is achieved, but weight becomes excessively high
Solution Approach 1:
The fan case uses composite materials consisting of multiple layers including composite containment layers, a metallic backing plate, and a ballistic liner. This composite construction provides the necessary containment capability for fractured fan blades while significantly reducing weight compared to a purely metallic construction.
Solution Approach 2:
Different regions of the fan case have different material properties optimized for their specific functions. The containment layers provide lightweight structural integrity, the metallic backing plate provides precise mounting surfaces, and the ballistic liner provides impact resistance. This local optimization achieves reliable containment with reduced overall weight.
3Strength
If threaded fasteners are used to attach components, then secure attachment is achieved, but the composite material is not accommodating of bolt holes
Solution Approach 1:
A metallic backing plate serves as an intermediary that bridges the composite material and the threaded fastener system. The backing plate contains precisely located bolt holes and threading that accommodate standard fasteners, while the composite layers are attached to the backing plate. This enables secure mechanical attachment without requiring the composite material itself to be accommodating of bolt holes.
Solution Approach 2:
The design merges the metallic backing plate with the composite containment layers through adhesive bonding and mechanical interlocking. This combination creates a unified structure where the metallic plate provides the fastening interface and the composite layers provide the containment function, achieving both secure attachment and lightweight construction.
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 solution enables reliable and secure attachment of components to the composite fan case, providing effective containment of fan blades while reducing weight and maintaining structural integrity, addressing the limitations of existing composite material manufacturing techniques.
Implementation Method 1
The boss is attached to the outer surface with at least one fiber reinforce ply and an adhesive
Data Source
AI summary
A fan case for a gas turbine engine includes a composite fan containment case having an outer surface, a front and a rear. An attachment flange and a mounting ring are respectively provided on the front and the rear. A bolt attachment is supported on the outer surface. The composite fan containment case has a containment area that is configured to be axially aligned with a fan blade. A ballistic liner is arranged in the containment area.