Composite Fan Case Bolt Attachment Using Metallic Inserts
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Solution Overview
Problem
Composite fan cases in gas turbine engines pose challenges in accommodating threaded bolt holes for attaching external components due to their material properties, which hinder secure and reliable fastening.
Innovation Solution
A composite fan case design incorporating molded conical 'bathtub' bosses with embedded metallic inserts and a combination of fiberglass plies and adhesive, along with helical or key-lock inserts, allows for secure threaded attachments by forming a strong bond and preventing rotation, enabling reliable mounting of external components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If threaded bolt holes are created directly in the composite fan case, then weight reduction is achieved, but the structural integrity and reliability of fastening are compromised
Solution Approach 1:
The solution employs a hybrid composite structure combining composite material (for weight reduction) with metallic inserts (for fastening reliability). The metallic inserts are embedded within the composite fan case, creating a multi-material system that leverages the advantages of both materials: the composite provides lightweight properties while the metal inserts provide threaded fastening capability and structural strength.
2Reliability
If metallic inserts are embedded in the composite fan case, then secure threaded attachments are enabled, but device complexity increases
Solution Approach 1:
The manufacturing process merges multiple operations into an integrated sequence: metallic inserts are positioned within the composite fan case, adhesive is applied to bond the inserts, and the assembly is cured in one continuous process. This merging of operations, while creating a multi-component structure, streamlines production and reduces overall system complexity compared to post-assembly fastening methods.
3Strength
If adhesive bonding is used to secure metallic inserts, then strong bond is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The metallic inserts are positioned and secured with adhesive before the final curing process. This preliminary positioning allows for adjustment and alignment verification before the adhesive sets, ensuring proper placement while maintaining the strength benefits of adhesive bonding. The sequence of operations is designed to accommodate precision requirements at the appropriate stage of manufacturing.
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
This solution provides a robust and secure method for attaching external components to the composite fan case, ensuring reliable fastening and weight reduction while maintaining structural integrity.
Implementation Method 1
a combination of fiberglass plies and adhesive
Implementation Method 2
helical or key-lock inserts, allows for secure threaded attachments by forming a strong bond and preventing rotation
Data Source
Figure 1A
Figure 1B~1C
Figure 2A~2C
AI summary
A composite fan case (20) and a method of attaching a bolt attachment (22) to a composite fan case (20) in a gas turbine engine include a composite fan case body having an outer surface. The bolt attachment (22) is attached to the outer surface of the fan case (20) and has an internal composite boss (30) with at least one threaded metallic insert (32). The boss (30) is attached to the outer surface of the fan case with a combination of fiber reinforced ply and adhesive.