Segmented Elastomeric Mandrel for Composite Curing
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Solution Overview
Problem
Existing mandrels for curing composite parts often fail to apply consistent pressure, leading to thickness variations and bulging due to non-uniform expansion, and are difficult to handle and remove, especially when they are not shaped to accommodate thermal expansion and geometric constraints.
Innovation Solution
A segmented mandrel body composed of elastomeric components with compressible interconnections that allow axial expansion due to thermal expansion, ensuring uniform pressure distribution and easy extraction by contracting after cure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a solid mandrel is used for curing composite parts, then the mandrel can maintain structural integrity, but it cannot provide uniform pressure distribution during curing
Solution Approach 1:
The mandrel is divided into multiple expandable segments or zones that can independently adjust their expansion characteristics. This segmentation allows different regions of the mandrel to apply pressure uniformly across the composite part surface, resolving the contradiction between maintaining structural integrity and achieving uniform pressure distribution.
2Adaptability or versatility
If a flexible mandrel material is used to conform to part contours, then the mandrel can adapt to complex geometries, but it becomes difficult to handle and remove after curing
Solution Approach 1:
The mandrel employs dynamic expansion and contraction capabilities through expandable segments that can change their volume or shape. During curing, the mandrel expands to conform to complex part contours and apply uniform pressure. After curing, the mandrel contracts to reduce its size, making it easier to handle and remove from the cured composite part.
3Force
If the mandrel is designed to expand during curing, then pressure can be applied to consolidate the composite, but non-uniform expansion causes thickness variations and bulging
Solution Approach 1:
The mandrel is divided into multiple independently controllable segments that can expand in a coordinated manner. This segmentation allows precise control over the expansion pattern, ensuring uniform pressure application across the composite part surface and preventing localized over-expansion that would cause bulging or thickness variations.
Solution Approach 2:
Different segments of the mandrel can be designed with different expansion characteristics, coefficients of thermal expansion, or actuation mechanisms tailored to the specific requirements of different regions of the composite part. This local customization ensures uniform pressure distribution and prevents thickness variations while maintaining the ability to apply consolidation pressure.
4Weight of moving object
If a vented bladder mandrel is used to apply pressure, then the mandrel can be lightweight and flexible, but it may leak during curing and cannot provide consistent pressure
Solution Approach 1:
The mandrel uses multiple sealed expandable segments instead of a single vented bladder. Each segment is independently sealed and can be pressurized through controlled pathways, eliminating the leakage issues associated with vented bladders while maintaining lightweight and flexible characteristics. The segmented design also allows for more consistent pressure distribution.
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 provides consistent and uniform pressure during curing, preventing bulging and ensuring high-quality composite parts with improved handling and extraction capabilities, while being lightweight, flexible, and cost-effective.
Implementation Method 1
The compressible interconnections allow the plurality of elastomeric components to expand axially due to thermal expansion resulting in a distribution of pressure
Data Source
AI summary
An example mandrel for processing a part is described including a plurality of elastomeric components aligned end to end and spaced apart linearly to form a segmented mandrel body, and compressible interconnections positioned within spacing between adjacent elastomeric components and abutting the adjacent elastomeric components. The compressible interconnections allow the plurality of elastomeric components to expand axially due to thermal expansion resulting in a distribution of pressure. An example method for fabricating a composite part is also described including placing a base composite layer into a cavity of a tooling surface, inserting a mandrel into the cavity of the tooling surface such that the base composite layer is between the mandrel and the tooling surface, applying a skin to the mandrel and the base composite layer forming a package, enclosing the package in a vacuum bag and curing, and removing the mandrel from the cavity of the tooling surface.