Machinable CMC Insert with Polymer Char Bonding
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Solution Overview
Problem
Ceramic matrix composite (CMC) components in gas turbine engines face challenges with machining, as it exposes fibers and leads to cracks and reduced tolerance, necessitating the development of a method to bond a machinable insert to the CMC without attacking the fibers.
Innovation Solution
A ceramic matrix composite assembly is created by sandwiching a polymer char between the CMC component and a monolithic insert, where the insert is bonded to the exterior surface of the CMC using a pre-ceramic polymer that forms a polymer char upon heating, forming a continuous ceramic matrix to prevent fiber exposure and degradation during machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If CMC components are machined directly, then machining can be performed, but fibers are exposed and cracks occur reducing tolerance
Solution Approach 1:
A monolithic insert made of machinable CMC material is bonded to the exterior surface of the CMC component, serving as an intermediary layer that can be machined without exposing or damaging the underlying CMC fibers. This mediator allows machining operations to proceed while protecting the structural integrity and tolerance of the main component.
Solution Approach 2:
The CMC component is divided into two functional parts: the main CMC component that maintains structural integrity and the separate monolithic insert that handles machining operations. This segmentation allows each part to be optimized for its specific function - the insert for machinability and the component for structural performance.
2Reliability
If a bonding method is used to attach insert to CMC, then the insert protects fibers during machining, but the bonding process must not attack or degrade the CMC fibers
Solution Approach 1:
A polymer char layer is applied between the monolithic insert and the CMC component exterior surface. This polymer char creates an inert barrier that prevents chemical interaction and potential degradation of the CMC fibers during the bonding process, while still allowing effective bonding of the insert to the component.
3Reliability
If polymer char is sandwiched between insert and CMC component, then bonding is achieved without fiber attack, but additional material and processing steps are required
Solution Approach 1:
The polymer char layer undergoes thermal transformation during processing, changing from a polymer state to a charred ceramic-like state that provides both bonding functionality and fiber protection. This parameter change allows a single material to fulfill multiple functions - bonding the insert while protecting the CMC fibers from chemical attack.
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 allows for machining of CMC components without exposing fibers, reducing the risk of cracks and maintaining tolerance, thereby enhancing the durability and performance of gas turbine engine components.
Implementation Method 1
heating the pre-ceramic polymer to form a polymer char that bonds the insert to the ceramic preform
Implementation Method 2
forming a continuous ceramic matrix to prevent fiber exposure and degradation during machining
Data Source
AI summary
An assembly comprising a ceramic matrix composite component, a monolithic insert, and a polymer char and a method for producing the same. The ceramic matrix composite component may include an exterior surface, with the monolithic insert bonded to the exterior surface of the ceramic matrix composite component. The polymer char may be sandwiched between the monolithic insert and the exterior surface of the ceramic matrix composite that may bond the monolithic insert to the ceramic matrix composite component.