Fiber Steering for CTE Matching in Composite-Metal Joints
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Solution Overview
Problem
Existing methods for joining composite structures with metallic structures face challenges due to significant differences in coefficients of thermal expansion (CTE), leading to deleterious effects in environments with temperature variations, and often require heavy and costly adapters to mitigate these issues.
Innovation Solution
The solution involves creating composite assemblies with a uniform CTE in one region and a variable CTE in another, achieved through fiber steering in multiple plies, allowing for a gradual change in CTE across different regions, eliminating the need for additional adapters and reducing weight and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal expansion adapters are used between composite structures and metallic structures, then the CTE mismatch is accommodated, but the assembly weight increases and manufacturing complexity increases
Solution Approach 1:
The patent extracts the CTE-matching function from a separate adapter component and integrates it directly into the composite structure through fiber steering. By taking out the need for an intermediate adapter and embedding the solution within the composite laminate itself, the design eliminates additional weight while maintaining CTE compatibility at the interface.
Solution Approach 2:
The patent merges the structural function with the CTE-matching function into a single integrated composite structure. Instead of having separate structural elements and separate CTE-compensation elements, the fiber-steered composite laminate simultaneously provides both structural support and thermal expansion matching, eliminating the need for additional adapters.
2Reliability
If thermal expansion adapters are used between composite structures and metallic structures, then the CTE mismatch is accommodated, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent changes the fiber orientation parameters within the composite laminate to achieve CTE matching. By adjusting the fiber angles and distribution in specific plies, the effective thermal expansion properties of the composite are tailored to match the metallic structure, providing a more straightforward manufacturing approach compared to fabricating and assembling separate adapter components.
Solution Approach 2:
The patent utilizes composite material properties and anisotropy to achieve CTE matching. By leveraging the directional properties of fiber-reinforced composites and steering fibers in specific patterns, the design creates a region with customized thermal expansion characteristics that match the metallic structure, simplifying the overall assembly approach.
3Manufacturing precision
If fiber angles are changed in plies to achieve variable CTE, then the CTE matching is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent segments the composite laminate into distinct regions with different fiber steering patterns. By dividing the structure into zones with specific fiber orientations (such as +/-45 degree plies near the interface), the manufacturing process can target specific areas for complex fiber steering while keeping other regions simpler, thereby achieving precise CTE matching without requiring the entire structure to be manufactured with equal complexity.
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 approach effectively matches the CTE of composite structures with metallic structures, reducing thermal expansion mismatches and associated stresses, while maintaining structural integrity and reducing manufacturing complexity and weight.
Implementation Method 1
The CTE variation with the second composite structure may be achieved by changing fiber angles in at least one ply extending through all three regions. For example, at least one of the plies may be subjected to fiber steering.
Implementation Method 2
The second structure is formed from a composite material that includes a first ply and a second ply... The fiber angle in the overlap region in the first fiber ply is different from a fiber angle in the baseline region in the first fiber ply such that the overlap region of the second structure has a CTE substantially matching the CTE of the first structure
Implementation Method 3
It should be noted that the second structure may have different CTE values in different directions, if the material forming the second structure is an anisotropic material.
Data Source
AI summary
Provided are assemblies, each including a first structure having a uniform coefficient of thermal expansion (CTE) and a second composite structure having a variable CTE. Also provided are methods of forming such assemblies. The second structure has overlap, transition, and baseline regions. The overlap region directly interfaces the first structure and has a CTE comparable to that of the first structure. The baseline region is away from the first structure and has a different CTE. Each of these CTEs may be uniform in its respective region. The transition region may interconnect the baseline and overlap regions and may have gradual CTE change from one end to the other. The CTE variation with the second composite structure may be achieved by changing fiber angles in at least one ply extending through all three regions. For example, any of the plies may be subjected to fiber steering.