Reusable Metal Retainers for Co-bonding Uncured Stringers
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Solution Overview
Problem
Existing retainers used in the co-bonding of composite stringers in aircraft manufacturing are difficult to remove, result in poor surface quality, and need to be replaced for each manufactured specimen, with issues in adapting the vacuum bag to the stringer ends and prone to undesired movements during the curing process.
Innovation Solution
Reusable metal retainers with a geometry matching the stringer cross-section and an inclined plane between 30° and 60°, incorporating metallic sheets and magnets for secure placement, allowing a mild vacuum bag transition and preventing resin and adhesive flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If cork or airpad retainers are used to prevent resin flow, then resin flow is prevented, but the retainers are difficult to remove and require cutting, resulting in poor surface quality
Solution Approach 1:
The patent replaces the disposable cork/airpad retainers with reusable metal retainers. Although metal is more expensive per unit, the ability to reuse them eliminates the need for cutting and removal operations, improving ease of operation while maintaining effective resin flow prevention
Solution Approach 2:
The patent changes the material parameter from soft/compressible materials (cork, airpad) to rigid metal materials. This parameter change allows the retainer to maintain its shape and be easily removed without deforming or requiring cutting, while still effectively preventing resin flow
2Object-affected harmful factors
If cork or airpad retainers are used, then resin flow is prevented, but new retainers must be manufactured for each specimen, increasing production time and cost
Solution Approach 1:
The patent implements a system where metal retainers are recovered and reused across multiple production cycles. The retainers are not discarded after single use like traditional cork or airpad retainers, but are instead cleaned and reused, significantly improving productivity and reducing manufacturing costs
Solution Approach 2:
The metal retainers are designed with universal applicability across different stringer specimens. A single retainer design can be used on multiple stringers, eliminating the need to manufacture new retainers for each specimen and improving overall production efficiency
3Object-affected harmful factors
If traditional retainer geometry is used, then resin flow is prevented, but the vacuum bag cannot adapt properly to the stringer ends, causing breakage
Solution Approach 1:
The patent modifies the retainer geometry to include curved or rounded transitions at the ends, allowing the vacuum bag to follow a mild contour rather than sharp angles. This curvature enables the vacuum bag to adapt properly to the stringer ends without causing breakage, while the retainers continue to effectively prevent resin flow
4Object-affected harmful factors
If traditional retainer placement is used, then resin flow is prevented, but undesired movements occur during vacuum bag displacement
Solution Approach 1:
The patent replaces traditional mechanical retention methods with magnetic retention. Magnets are embedded in the metal retainers, allowing them to be securely held in position during vacuum bag displacement without physical contact or mechanical fastening, preventing undesired movements while maintaining effective resin flow prevention
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 reusable metal retainers provide better surface quality, easier installation and removal, adapt well to the stringer ends, and prevent undesired movements, eliminating the need for new retainers with each specimen and enhancing vacuum bag compatibility.
Implementation Method 1
incorporating metallic sheets and magnets for secure placement
Implementation Method 2
a vacuum bag film. The material of the vacuum bag film is a very thin film with a great elongation capacity to adapt perfectly to the invar geometry
Data Source
AI summary
A re-usable retainer designed to be used in the curing process of co-bonding uncured stringers. The re-usable retainer is made of metal so it is not necessary to manufacture one retainer for each manufactured stringer. The metallic retainer is placed in direct contact with the uncured resin so the cured stringer has a very good surface quality.The re-usable retainer has a special shape that allows a mild transition of the vacuum bag that avoids vacuum bag breakages. The re-usable retainer is easy to install and to remove.