Graded CTE Composite Interface for Thermal Stress Reduction
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Solution Overview
Problem
Attaching materials with vastly different coefficients of thermal expansion (CTE) in extreme environments is challenging due to the development of significant thermal stresses and strains, often requiring complex and non-rigid mechanical fastening devices that are not suitable for high-temperature applications.
Innovation Solution
A graded coefficient of thermal expansion (CTE) interface is created using a composite structure with multiple layers, fabricated through metal deposition or powder metallurgy techniques, to produce a billet or near net shape that can be processed for attachment of structural members with different CTEs, allowing for a rigid assembly without complex mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If complex mechanical fastening devices are used to attach members with different CTEs, then the assembly can accommodate relative movement during heating or cooling, but the device complexity increases and the structure becomes non-rigid
Solution Approach 1:
The patent applies parameter changes by creating a composite structure with gradually varying material composition and CTE properties across its thickness. The composite structure contains layers with different CTE values arranged in a gradient pattern, allowing the CTE parameter to transition smoothly from one value at the first interface to another value at the second interface. This gradual parameter change enables the composite structure to accommodate differential thermal expansion between dissimilar components without requiring complex mechanical fastening devices.
Solution Approach 2:
The patent employs composite materials by constructing an intermediate structure from multiple layers of materials with different CTE properties. The composite structure is formed by stacking layers with progressively varying composition and thickness, creating a graded material system. This composite approach allows the structure to exhibit intermediate CTE values that bridge the gap between components with vastly different thermal expansion characteristics, eliminating the need for complex accommodation mechanisms.
2Reliability
If composite structures with graded CTE are used to attach members with vastly different CTEs, then thermal stresses and strains are reduced, but the manufacturing complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the intermediate composite structure into multiple discrete layers, each with a specific material composition and CTE value. Rather than attempting to create a continuously graded material, the invention segments the transition into distinct steps, where each layer contributes to the overall CTE gradient. This segmentation simplifies manufacturing by allowing each layer to be fabricated separately using conventional techniques and then stacked to form the complete graded structure.
Solution Approach 2:
The patent implements local quality by varying the material composition and layer thickness at different positions through the composite structure's thickness. Each local region (layer) has tailored properties optimized for its specific position in the CTE gradient. The local quality approach allows different sections of the composite to have different mechanical and thermal characteristics, with the composition and thickness of each layer carefully controlled to achieve the desired CTE transition while maintaining manufacturability.
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 enables the attachment of structural members with vastly different CTEs, allowing for heating or cooling without significant thermal stresses or strains, and eliminates the need for complicated mechanisms, resulting in a cost-effective and weight-efficient solution for extreme environment applications.
Implementation Method 1
a graded coefficient of thermal expansion (CTE) interface is provided by a composite structure... Multiple layers with graded CTE are selected and build-up fabrication processes are employed... The resulting assembly provides capability for attaching structural members with vastly different CTE to produce an assembly that can be heated or cooled without introducing significant thermal stresses or strains
Data Source
AI summary
An integrated composite structure with a graded coefficient of thermal expansion (CTE) is formed by selecting a plurality of layers of materials with a graded CTE and using build-up (bottom-up) fabrication approaches such as metal deposition or powder metallurgy to produce a CTE-graded layered composite preform, which is then consolidated and heat treated to create the CTE graded integrated composite billet or near net shape. The integrated composite billet or near net shape is then processed to produce a first surface for attachment of a first structural member having a first CTE and to produce a second surface of for attachment of a second structural member having a second CTE.