Expandable Tube Core for Stringer Layup Without Fiber Bridging
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Solution Overview
Problem
Current methods for manufacturing composite components with thermoforming skins and stringers face issues such as fiber bridging and undulations during layup, adherence of cores to skins, and high costs due to frequent core exchange, leading to inefficiencies in high-rate manufacturing.
Innovation Solution
A flexible tubular core with a reinforcement member, expandable to match the shape of the stringer, which withstands layup pressure and is collapsible post-curing, providing support and geometrical definition, and is reusable, suitable for various manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a semi-rigid core material is used to support the layup process, then the layup process is supported, but the core adheres between stringers and skins causing fiber bridging and undulations
Solution Approach 1:
The patent employs a flexible membrane instead of a semi-rigid core material. This membrane provides the necessary support during layup while being compliant enough to prevent fiber bridging and undulations. The flexible nature allows it to conform to the stringer geometry without creating the adhesion problems associated with rigid cores.
Solution Approach 2:
The flexible membrane acts as an intermediary between the stringer core and the composite skin. It provides the necessary geometric definition and support during manufacturing while preventing direct adhesion between the core material and the skin, thereby eliminating fiber bridging issues.
2Ease of operation
If tube cores are placed inside cavity following 'Lay over the hollow' constraint, then the layup process is simplified, but bridging and undulations of fibers occur during skin layup
Solution Approach 1:
The flexible membrane maintains the simplified 'Lay over the hollow' approach while resolving the fiber bridging issue. Its flexibility allows it to accommodate the layup process simplicity while preventing the undulations that occur with rigid tube cores.
3Strength
If state-of-the-art cores are used, then the core provides structural support, but they adhere between stringers and skins leading to high cost for core exchange
Solution Approach 1:
The flexible membrane provides structural support during the manufacturing process while its non-adhesive properties prevent bonding to the skin. This allows for easier core removal and reuse, improving productivity and reducing costs associated with frequent core exchange.
4Manufacturing precision
If a rigid core is used to maintain geometry during curing, then geometrical definition is maintained, but the core cannot be removed or reused efficiently
Solution Approach 1:
The membrane transitions from a rigid-like state during curing (maintaining geometrical definition) to a flexible, removable state afterward. This dynamic behavior allows it to provide the necessary geometric definition during manufacturing while enabling easy removal and reuse for subsequent production cycles.
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 waste reduction, lower recurring costs, improved laminate quality, better cycle times, and enhanced demolding capabilities, with potential for automation.
Implementation Method 1
a flexible tube core (10c) configured to be expandable to essentially the same shape as the closed-profile thermoforming stringer
Implementation Method 2
the reinforcement member (10r) is configured to withstand layup pressure over the hollow portion (20h) so that a minimum layup pressure can be realized while keeping geometrical shape of the thermoforming base layer (30)
Data Source
AI summary
A flexible tube element for insertion into a hollow portion enclosed between a first principal surface of a thermoforming base layer and a protruding part of a closed-profile thermoforming stringer, wherein the closed-profile thermoforming stringer has a base part attached to the first principal surface. The flexible tube element includes a flexible tube core configured to be expandable to essentially the same shape as the closed-profile thermoforming stringer; and a reinforcement member disposed only in an area of the flexible tube element that faces the first principal surface of the thermoforming base layer.