CMC Turbine Blade Platform Assembly for Interlaminar Stress Relief
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Solution Overview
Problem
Ceramic Matrix Composite (CMC) turbine blades face challenges in attaching a platform due to low interlaminar strengths, leading to high internal interlaminar stresses and limited functionality, as the bending of the platform causes stress concentrations at the blade root region, limiting the platform's operational duration.
Innovation Solution
A ceramic matrix composite blade design is proposed, separating the airfoil/root assembly from the platform assembly, with the platform assembly being a three-dimensional woven preform bonded to the airfoil/root assembly, using a silicon interfacial layer for enhanced interlaminar tensile strength and distributing attachment loads across a larger root region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a platform is attached to a laminated CMC blade, then the platform can support blade-to-blade dampers and form the inner flowpath, but the low interlaminar strengths of CMC cause high internal interlaminar stresses that limit the platform's functional duration
Solution Approach 1:
The blade is divided into two separate assemblies: an airfoil/root assembly and a platform assembly. This segmentation allows each component to be optimized independently for its specific loading conditions, preventing the platform from imposing bending stresses on the laminated airfoil/root structure while maintaining full platform functionality.
Solution Approach 2:
The platform assembly is constructed using three-dimensional woven CMC material, which provides superior interlaminar strength compared to traditional laminated structures. This composite material approach enables the platform to withstand centrifugal and bending loads without the interlaminar stress problems that plague laminated constructions.
2Device complexity
If the platform is integrally woven into the airfoil region, then the structure is simplified, but the fibers at the intersection are exposed to both large radial loads and local bending stresses, limiting the design capability
Solution Approach 1:
Rather than integrating the platform into the airfoil region, the design segments the structure into separate airfoil/root and platform assemblies. This eliminates the problematic fiber intersection zone where radial and bending loads would combine, allowing fibers in each assembly to be oriented optimally for their respective load paths.
Solution Approach 2:
The airfoil/root assembly uses a laminate construction optimized for radial tension loads, while the platform assembly uses three-dimensional woven construction optimized for handling bending and centrifugal loads. Each region has a material structure tailored to its specific mechanical environment.
3Ease of operation
If the platform extends outward from the airfoil as a cantilevered structure, then the platform can be attached to the root region, but the combined load creates large bending stresses at the platform-blade root interface
Solution Approach 1:
The platform is separated from the airfoil/root assembly into an independent platform assembly. This segmentation moves the platform's attachment point away from the stressed airfoil-root interface, allowing the platform to be supported by the disk attachment region instead, thereby eliminating the compounding bending stresses at the original interface.
Solution Approach 2:
The platform assembly acts as an intermediary structure between the airfoil/root assembly and the disk attachment. It transfers loads directly to the disk attachment region, bypassing the airfoil-root interface and reducing bending stresses at that critical location.
4Stress or pressure
If the platform assembly is extended to cover the attachment region, then complex bending stresses are distributed over a larger region, but the platform must be bonded to the airfoil/root assembly requiring enhanced interlaminar strength
Solution Approach 1:
The platform assembly is made from three-dimensional woven CMC material, which inherently provides superior interlaminar strength compared to traditional laminated structures. This material property enables the platform to be bonded to the airfoil/root assembly while withstanding the enhanced interlaminar stresses required for load transfer across the bond interface.
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 design minimizes interlaminar tensile stresses, increases the interlaminar tensile strength, and improves the structural performance of the blade by distributing complex bending stresses, thereby enhancing the operational capability of the ceramic matrix composite blade.
Implementation Method 1
using a silicon interfacial layer for enhanced interlaminar tensile strength
Data Source
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AI summary
A component (10) for use in a gas turbine engine includes an airfoil/root assembly (12, 14); a platform assembly structure (24) having an opening (30) which is bonded to the airfoil/root assembly.