Ceramic Composite Fastener Backlocking for Thermal Stress Relief
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Solution Overview
Problem
The mounting of ceramic and ceramic matrix composite parts in gas turbine engines faces challenges due to differential thermal expansion of metallic and non-metallic components, with existing fastening methods inducing undue tensional stresses in ceramic materials.
Innovation Solution
A method involving a fastener with a deformable head that is expanded within a compartment to backlock, using a pressurized fluid source to cause plastic deformation, reducing the risk of stress induction and enhancing securement without exposing the fastener to the gaspath.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fasteners are expanded inside a compartment by internal fluid pressure, then the fastener is securely locked to the ceramic body, but undue tensional stresses are induced into the ceramic material
Solution Approach 1:
The method performs preliminary actions by first drilling a cavity in the ceramic body, then inserting the fastener in an unexpanded state before expansion. This sequence allows the ceramic structure to be prepared and the fastener to be positioned before the expanding action occurs, reducing shock and stress induction into the ceramic material during the securing process
Solution Approach 2:
The patent introduces a fluid intermediary (gas or liquid under pressure) that is directed through a passage in the fastener to cause controlled expansion. This fluid mediator allows the expansion force to be applied gradually and uniformly through the fastener's internal passage, rather than applying external mechanical force that would directly stress the ceramic body
2Ease of manufacture
If metallic fasteners pass entirely through the non-metallic component, then the fastening is simple to implement, but differential thermal expansion causes stress and potential failure
Solution Approach 1:
The fastener system employs a nested structure where an expandable core is inserted through the ceramic body into a cavity, then expanded to lock in place. The fastener consists of nested components including a shank, head, and internal fluid passage, allowing the small expandable portion to be contained within the larger fastener assembly and ceramic cavity
Solution Approach 2:
The fastener utilizes parameter changes by transitioning from an unexpanded state (small diameter) to an expanded state (larger diameter) through internal pressurization. This dimensional parameter change allows the fastener to securely lock within the ceramic cavity after insertion, providing reliable attachment while accommodating thermal expansion differences between metallic and ceramic materials
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 effectively secures ceramic components while minimizing thermal stress and reducing the risk of fastener dislodgment, maintaining integrity and reducing the likelihood of damage to other components.
Implementation Method 1
a fastener 50 having a head 70 and a shank 52 extending from the head 70. The method inter alia comprises expanding a portion of the fastener 50. In some embodiments, the head 70 is expanded within a compartment 80 to backlock
Implementation Method 2
using a pressurized fluid source to cause plastic deformation
Data Source
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AI summary
Attaching a fastener (50) to a ceramic matrix composite or ceramic body by inserting a portion of the fastener (50) into a compartment of the body, the compartment having a first portion (82) and a second portion (84), the second portion (84) outboard of and narrower than the first portion (82); and delivering a fluid into the fastener (50) to expand a portion (70) of the fastener (50) within the compartment first portion (82).