Mandrel-Based Bladder Venting for Stiffened Composite Assembly
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Solution Overview
Problem
The conventional vacuum compacting process for assembling stiffened composite structures, such as aircraft fuselages, is labor-intensive and prone to leaks due to the need for perforating the flexible sheet to connect stringer bladders with vent lines, compromising the integrity of the vacuum and requiring frequent rework.
Innovation Solution
A network of fluid lines is configured to be selectively coupled to stringer bladders, extending through the layup mandrel and maintaining atmospheric access to bladder volumes, eliminating the need for perforations in the flexible sheet, and using covers to protect the components and maintain vacuum integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the flexible sheet is perforated to connect stringer bladders with vent lines, then the stringer bladders can be vented during vacuum compacting, but the integrity of the vacuum seal is compromised and leaks occur
Solution Approach 1:
A rigid mandrel with pre-formed channels serves as an intermediary structure between the stringer bladders and the vacuum environment. The mandrel's internal passageways provide dedicated venting pathways that eliminate the need to perforate the flexible vacuum sheet, thus maintaining vacuum seal integrity while enabling bladder venting functionality
Solution Approach 2:
The mandrel is pre-configured with venting channels and cavities before the vacuum compacting process begins. This preliminary structuring of venting pathways eliminates the need for temporary perforations in the flexible sheet during the process, preserving the vacuum seal while providing necessary venting capability
2Productivity
If the flexible sheet is used for vacuum compacting, then the stringers and skin can be compacted together, but the sheet requires frequent replacement due to wear and leaks
Solution Approach 1:
The rigid mandrel acts as a mediator that assumes the venting and structural support functions, allowing the flexible sheet to focus solely on providing the vacuum seal and compacting force. This division of functional responsibilities reduces the flexible sheet's operational stress and extends its service life
Solution Approach 2:
The invention shifts from using a disposable flexible sheet for all functions to using a durable rigid mandrel for structural and venting functions, allowing the flexible sheet to be reused multiple times without replacement, thereby extending overall system service life
3Reliability
If conventional vacuum compacting is used, then the stringers and skin can be cured, but the process is labor-intensive and time-consuming
Solution Approach 1:
The mandrel is pre-assembled with stringer bladders positioned in their correct locations within cavities before the skin is applied. This preliminary arrangement eliminates time-consuming adjustments and rework during the vacuum compacting process, reducing overall installation time while maintaining curing quality
Solution Approach 2:
The mandrel's structured design with integrated venting channels and bladder positioning features enables the system to self-align and self-vent during compacting, reducing the need for manual intervention and labor-intensive adjustments while maintaining reliable curing
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 reduces installation time, minimizes leaks, extends the life of the flexible sheet, and allows for multiple uses without replacement, enhancing the efficiency and reliability of the vacuum bagging process.
Implementation Method 1
A vacuum is then applied between the sheet of material and the inner mold line layup mandrel to compact the stringers and skin together
Data Source
AI summary
Systems (100) for assembling stiffened composite structures comprise a layup mandrel (102) and a network (104) of fluid lines (116) configured to be selectively and fluidically coupled to string bladders (118) positioned relative to the layup mandrel (102).