Ceramic Skin Panel Attachment for Thermal Expansion
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Solution Overview
Problem
Gas turbine engine nacelle systems face challenges in attaching ceramic matrix composite panels to metallic support structures due to differences in coefficients of thermal expansion, leading to relative expansion and movement issues during thermal cycling.
Innovation Solution
A mechanical connection system featuring a nut plate, bolt, collar, and washer configuration that allows for compressive attachment of ceramic skin panels to a metallic support structure, preventing rotation and deformation, and accommodating differential thermal expansion through a tapered surface design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a mechanical attachment mechanism is used to attach a ceramic panel to a metallic support structure, then the panel can be securely fastened, but the difference in coefficients of thermal expansion causes relative expansion and movement that leads to mechanical stress and potential failure
Solution Approach 1:
The patent introduces a compliant intermediary layer between the ceramic panel and metallic support structure. This layer acts as a mediator that absorbs the differential thermal expansion stresses, allowing the rigid ceramic panel to remain securely attached to the metallic structure without transmitting harmful mechanical stresses that would cause failure during thermal cycling.
Solution Approach 2:
The patent modifies the mechanical properties of the attachment system by introducing a compliant layer with specific elasticity and thickness parameters. By carefully selecting these parameters, the system can accommodate the thermal expansion differences between ceramic and metal while maintaining secure attachment, thus resolving the contradiction between attachment strength and thermal cycle reliability.
2Stability of the object's composition
If a rigid mechanical connection is used to prevent rotation of the ceramic skin panel, then the panel remains stable, but it may cause deformation that produces detrimental mechanical properties in the ceramic material
Solution Approach 1:
The patent carefully controls the thickness and compliance parameters of the intermediary layer to provide just enough flexibility that prevents rigid constraint-induced deformation of the ceramic panel, while still maintaining sufficient stability to prevent rotation and maintain proper positioning during thermal cycling.
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 system effectively secures ceramic skin panels to metallic structures without causing detrimental mechanical stress or deformation, ensuring reliable operation across varying temperatures and thermal cycles.
Implementation Method 1
the metallic portion will expand to a much greater degree than the ceramic panel as the structure is subjected to a high temperature environment
Implementation Method 2
the collar may be formed from an elastically deformable material and the collar may include a tapered inner surface
Data Source
Figure 1~2
Figure 3~4
Figure 5~5A
AI summary
A mechanical connection system is provided that includes a ceramic skin panel, at least one bushing, and at least one bolt. The ceramic skin panel includes a first surface, a second surface, and at least one aperture extending between the first surface and the second surface. The aperture has an axial centerline, a chamfered portion contiguous with the first surface, and an axial portion contiguous with the second surface. The chamfered portion includes a tapered surface disposed at a first angle such that a line extending along the tapered surface intersects the axial centerline at a plane of the second surface. The bushing has a housing and a collar. The housing is configured to mate with the chamfered portion of the aperture disposed within the ceramic skin panel. The collar is configured for engagement with the housing.