Aircraft Fastener with Ceramic Matrix Composite Cap for Low Observability
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Solution Overview
Problem
Metallic fasteners used to secure ceramic matrix composite components in aircraft exhaust gas flowpaths compromise the low observability properties due to exposed metal, which is not addressed effectively by existing solutions.
Innovation Solution
A fastener design featuring a metallic member with a non-metallic cap member, specifically a ceramic matrix composite cap, that is securely attached using a projection and deformation method, allowing the cap to cover the metallic head and reduce observability while maintaining structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metallic fasteners are used to secure CMC components, then structural strength and reliability are improved, but low observability properties are compromised due to exposed metal
Solution Approach 1:
The fastener is divided into two distinct parts: a metallic member (shaft and head) providing structural strength, and a non-metallic cap member providing low observability. This segmentation allows each part to fulfill its specific function without compromise.
Solution Approach 2:
The non-metallic cap member acts as an intermediary that covers the metallic head, mediating between the structural requirements (metal) and the observability requirements (non-metallic). The cap is retained by a projection on the metallic member, creating a composite fastener system.
2Object-affected harmful factors
If a non-metallic cap is added to cover the metallic head, then low observability properties are improved, but device complexity increases
Solution Approach 1:
The metallic member and non-metallic cap member are merged into a single integrated fastener assembly. The cap is retained by a projection extending from the metallic head, creating a unified structure that functions as one component while maintaining the benefits of material differentiation.
3Ease of manufacture
If the projection is deformed to retain the cap member, then manufacturing simplicity is improved, but the metallic member may be compromised
Solution Approach 1:
The projection undergoes a controlled parameter change through deformation (such as melting or plastic deformation) to transition from a retained state to a cap-securing state. This parameter change allows the projection to form an interference fit or mechanical lock with the cap without requiring additional fastening operations.
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 effectively reduces the observability of the fastener by covering the metallic head with a ceramic matrix composite cap, enhancing the low observability and thermal protection of aircraft components without compromising structural security.
Implementation Method 1
The deformation may comprise melting
Data Source
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AI summary
A fastener (26) has a metallic member (80) and a non-metallic cap member (82). The metallic member (80) has a head (94) and a shaft (86). The shaft (86) has a first end (90) at the head (94), a distal second end (88), and an externally threaded portion (92). The metallic member (80) further has a projection (102) extending from the head (94) opposite the shaft (86). The cap member (82) is mated to the head (94) opposite the shaft (86 and retained by the projection (102).