Ceramic Matrix Composite Pylon Fairing
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Solution Overview
Problem
The existing rear fairings for aircraft turbojet engine pylons face issues with high thermal gradients, differential thermal expansion, and mechanical weakness due to the use of metal materials, as well as delamination of ceramic matrix composite materials under mechanical stresses and vibrations.
Innovation Solution
A rear fairing made from ceramic matrix composite materials with inter-layer weaving threads forming a single preform that includes the floor and lateral walls, providing high mechanical strength and minimizing delamination risks, while also being lightweight and resistant to chemical agents, with features such as sharp edges for gas flow separation and optional transverse partitions for enhanced structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal materials are used for the rear fairing, then mechanical strength is sufficient, but the fairing becomes heavy and exhibits significant differential thermal expansion
Solution Approach 1:
The patent applies composite materials (specifically ceramic matrix composites or metal matrix composites) to replace traditional metal materials in the rear fairing. This allows achieving both reduced weight and maintained mechanical strength, while also reducing differential thermal expansion between different materials. The composite structure combines lightweight properties with structural integrity.
2Weight of moving object
If ceramic matrix composite materials are used for the rear fairing, then weight is reduced and thermal expansion is minimized, but mechanical strength between fabric layers is weak causing delamination
Solution Approach 1:
The patent applies local quality by using three-dimensional inter-layer weaving threads specifically at the interfaces between fabric layers, rather than throughout the entire structure. This targeted reinforcement provides delamination resistance where it is most needed (at layer interfaces) while maintaining the overall lightweight advantage of ceramic matrix composites.
Solution Approach 2:
The patent transitions from two-dimensional fabric layers to three-dimensional inter-layer weaving, adding a vertical dimension of connectivity between layers. The weaving threads pass through multiple layers in the thickness direction, creating mechanical interlocking that prevents delamination while maintaining the lightweight composite structure.
3Stability of the object's composition
If traditional metal fairing structure is used, then structural integrity is maintained, but differential thermal expansion between different materials causes significant expansion differences
Solution Approach 1:
The patent applies homogeneity by using composite materials throughout the entire rear fairing structure, including the floor, lateral walls, and transverse partitions. This uniform material composition ensures consistent thermal expansion characteristics across all components, eliminating the differential thermal expansion problems that arise from joining dissimilar metals with different expansion coefficients.
4Ease of manufacture
If ceramic matrix composite preform is used without inter-layer weaving, then manufacturing is simpler, but delamination occurs under mechanical stresses and vibrations
Solution Approach 1:
The patent enhances the preform structure by incorporating three-dimensional inter-layer weaving threads that extend in the thickness direction between fabric layers. This adds a third dimension of structural connectivity while maintaining compatibility with conventional preform manufacturing processes, achieving both manufacturing feasibility and delamination resistance.
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 offers a lightweight, mechanically robust, and thermally stable rear fairing with reduced risk of delamination, capable of withstanding high temperatures and vibrations, and provides an aerodynamic surface with acoustic treatment, effectively addressing the limitations of previous materials.
Implementation Method 1
The preforms have inter-layer weaving threads connecting the layers to each other
Implementation Method 2
Compared to the metal materials, the ceramic matrix composite materials CMC are much lighter, and have reduced thermal expansions
Implementation Method 3
The preform includes, in one single piece, the floor and the lateral walls which extend from each other by folds at least partially forming sharp edges protruding outwardly of the lateral walls
Data Source
AI summary
An rear fairing for a pylon supporting an aircraft turbojet engine forms an aerodynamic surface covering the base of the pylon. The rear fairing is elongated in a longitudinal direction and includes a floor arranged opposite the hot gases exiting the turbojet engine and side walls constituting aerodynamic surfaces. The floor and the side walls include ceramic matrix composite materials made from preforms formed by layers of superimposed warp and weft yarns, the preforms have interlayer weaving yarns connecting the layers to one another.