Segmented Mandrel for High-Temperature Bonding
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Solution Overview
Problem
The delta-alpha high temperature bonding process faces challenges in forming axisymmetric composite shells with complex curvatures, as existing methods require constructing shells in multiple sections, leading to increased weight, production time, and cost due to the need for connecting hardware and girth seam welds.
Innovation Solution
A segmented mandrel assembly with multiple segments that form a continuous outer surface, allowing for the bonding of composite shells with complex curvatures in a single piece by differential thermal expansion, eliminating the need for girth seam welds and reducing part count and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a one-piece inner mandrel is used for bonding composite shells with complex curvatures, then the shell can be formed as a single piece without girth seam welds, but the mandrel becomes entrapped within the bonded shell structure and cannot be extracted
Solution Approach 1:
The mandrel is divided into multiple separable segments that can be assembled around the shell components during bonding, then disassembled and extracted from the completed shell. This segmentation allows the mandrel to provide continuous support during the bonding process while enabling easy removal after bonding, resolving the contradiction between forming a single-piece shell and extracting the mandrel.
2Ease of operation
If composite shells with complex curvatures are constructed in multiple sections, then the mandrel can be extracted from open ends, but the shell requires connecting hardware and girth seam welds that increase weight and production time
Solution Approach 1:
The mandrel is segmented into multiple removable sections that can be extracted from the completed shell, allowing the shell to be formed as a single continuous piece without requiring girth seam welds or connecting hardware. This eliminates the additional weight from joints and fasteners while maintaining ease of mandrel removal.
Solution Approach 2:
The mandrel segments are designed to be movable and reconfigurable, transitioning from a fixed assembled state during bonding to a disassembled extractable state after bonding. This dynamic capability allows the system to achieve both single-piece shell formation and mandrel extraction without compromising structural integrity.
3Ease of operation
If composite shells with complex curvatures are constructed in multiple sections, then the mandrel can be extracted, but the production time and cost increase due to additional joining operations
Solution Approach 1:
The segmented mandrel enables single-piece shell formation, eliminating the need for post-bonding joining operations such as girth seam welding or hardware installation. This reduces production time and cost while maintaining the ability to extract the mandrel through segment disassembly.
Solution Approach 2:
The shell is formed as a complete single-piece structure during the bonding process itself, rather than requiring subsequent assembly operations. The segmented mandrel facilitates this preliminary formation while maintaining extractability, thereby eliminating later joining steps and reducing overall production time.
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
Enables the production of lightweight, single-piece composite shells with complex curvatures efficiently, reducing production time and costs by avoiding the use of connecting hardware and girth seam welds, while maintaining structural integrity.
Implementation Method 1
As the layered components and mandrel are heated to an elevated temperature, the difference between coefficients of thermal expansion of the layered components and the mandrel causes the inner mandrel to thermally expand more than the layered components.
Implementation Method 2
As the layered components and mandrel cool, the mandrel contracts in size, and the one-piece inner mandrel can be extracted from one end of the bonded shell, thereby releasing the bonded shell from the mandrel.
Data Source
AI summary
A method for bonding a composite multi-layer shell having complex curvature by the delta-alpha high temperature bonding process uses a novel tool. The tool includes a plurality of segments that combine to form a mandrel assembly having a substantially continuous outer surface. The outer surface has a substantially axisymmetric shape including a complex curvature. When the segments are combined to form the mandrel assembly, at least one of the segments is configured to be movable in a substantially inward direction without substantial obstruction by any other segment. The segments are constructed of a first material have a first coefficient of thermal expansion that is greater than a second coefficient of thermal expansion of a second material of a composite multi-layer shell to be bonded together using the tool.