Adjustable Bladder Vent Plugs for Void-Free Composite Stringer Filling
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Solution Overview
Problem
Conventional stringer bladders used in vacuum compacting processes for stiffened composite structures often shrink during curing, leading to incomplete cavity filling and potential voids, and the vacuum bagging process is labor-intensive with numerous leak points due to perforated vent lines.
Innovation Solution
A network of fluid lines is selectively coupled to stringer bladders, with bladder vent plugs and covers to maintain atmospheric pressure, preventing collapse and leakages, while adjustable bladder vent plugs accommodate shrinkage, ensuring complete cavity filling and efficient vacuum compaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional stringer bladders are used in vacuum compacting process, then the bladder can be sealed to maintain vacuum, but the bladder shrinks during curing causing incomplete cavity filling and voids
Solution Approach 1:
The bladder vent plug incorporates an adjustable elongate conduit that can slide within the main body bore, allowing the vent passage length to be dynamically adjusted. This enables the system to compensate for bladder shrinkage by extending the vent line to maintain fluid communication with the bladder interior throughout the curing process, ensuring continuous cavity filling despite dimensional changes in the bladder.
Solution Approach 2:
The invention changes the parameter of vent passage configuration by providing an adjustable conduit length and position. The elongate conduit can be positioned at different depths within the main body bore to accommodate varying bladder shrinkage levels, thereby maintaining optimal venting and filling conditions throughout the curing process.
2Ease of operation
If vent lines are connected to stringer bladders through perforated bags, then the bladders can be vented to atmosphere, but numerous leak points are created compromising vacuum integrity
Solution Approach 1:
The invention extracts the vent line connection from the flexible bag material and relocates it to a rigid structural component. The bladder vent plug with its main body and elongate conduit provides a dedicated venting pathway that does not require perforating the flexible bag, thereby eliminating the leak points while maintaining atmospheric venting capability through the rigid vent passage.
Solution Approach 2:
The bladder vent plug acts as an intermediary component between the stringer bladder and the external environment. It provides a controlled interface for atmospheric pressure equalization through the vent passage, eliminating the need for direct perforation of the flexible bag and thus preventing vacuum leaks while maintaining venting functionality.
3Productivity
If the vacuum bagging process uses perforated flexible sheets, then the stringers and skin can be compacted, but the sheet requires frequent replacement due to damage from perforations
Solution Approach 1:
The invention extracts the vent line connection points from the flexible bag material, eliminating the need for perforations. By providing venting capability through the rigid bladder vent plug structure, the flexible bag remains intact and undamaged, thereby extending its service life and reducing replacement frequency while maintaining compaction efficiency.
4Ease of manufacture
If conventional bladders are used without adjustment capability, then the assembly process is simple, but shrinkage causes voids requiring rework
Solution Approach 1:
The adjustable elongate conduit provides a simple yet effective mechanism for maintaining manufacturing precision. The conduit can be easily repositioned within the main body bore to accommodate bladder shrinkage, ensuring consistent cavity filling without complex procedures. This adjustable feature maintains filling consistency while preserving assembly simplicity through intuitive adjustment.
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 system reduces installation time, minimizes leaks, extends the life of vacuum bagging materials, and ensures consistent cavity filling, enhancing the assembly process efficiency and quality of stiffened composite structures.
Implementation Method 1
The elongate conduit is slidingly received within the main-body bore
Implementation Method 2
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 stringer bladders (118) positioned relative to the layup mandrel (102). Bladder vent plugs (300) are adjustable in length and are configured to close stringer bladders (118) except for fluid connection to the fluid lines (116).