Perforated Bulkhead Vacuum Bag for Composite Curing
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Solution Overview
Problem
The traditional Single Vacuum Bag process for curing epoxy matrix-based composites often results in voids due to inadequate volatile and air management, while existing Double Vacuum Bag Debulking techniques face issues with compaction pressure hindering volatile removal and sealing line detachment during the curing cycle, particularly in repair processes.
Innovation Solution
A system comprising an inner vacuum bag over the lay-up with a perforated bulkhead and an outer vacuum bag, where the outer bag applies slightly higher vacuum pressure to balloon the inner bag against the bulkhead, ensuring effective volatile and air extraction without detaching sealing lines, and incorporating a heating source for controlled curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the vacuum in the upper chamber is greater than the vacuum in the lower vacuum bag, then the trapped air and volatiles are more effectively removed, but the sealing lines of the inner bag detach from the working area
Solution Approach 1:
The patent introduces a rigid box as an intermediary structure positioned between the two vacuum chambers. This rigid box serves as a mediator that distributes the vacuum pressure from the outer chamber, preventing direct concentration of force on the inner bag's sealing lines. By placing the rigid box over the inner bag and connecting it to the outer chamber vacuum system, the pressure differential is managed more evenly, allowing effective volatile removal while protecting the sealing integrity of the inner bag.
2Object-generated harmful factors
If the outer vacuum bag applies higher vacuum pressure to balloon the inner bag, then volatile extraction is improved, but the inner bag may become unstable and detach sealing lines
Solution Approach 1:
The rigid box acts as a stabilizing intermediary between the outer and inner vacuum bags. When the outer bag applies higher vacuum pressure to balloon the inner bag for improved volatile extraction, the rigid box provides structural support that prevents excessive ballooning and instability. The rigid box distributes the pressure forces evenly, maintaining the inner bag's stability while still allowing sufficient volatile extraction.
Solution Approach 2:
The patent carefully controls the vacuum pressure parameters in both chambers. The outer chamber vacuum pressure is maintained at a level that provides sufficient force to balloon the inner bag for effective volatile removal, but not so high as to cause instability. The rigid box enables this parameter optimization by providing a stable intermediate structure that allows precise control of the pressure differential between the two chambers.
3Strength
If the inner vacuum bag is collapsed onto the tool with high pressure, then compaction is improved, but the removal of trapped air and volatiles is hindered
Solution Approach 1:
The patent divides the vacuum application into two separate chambers with independent pressure control. The inner vacuum bag can be collapsed onto the tool with high pressure for compaction, while the outer vacuum bag simultaneously or subsequently applies vacuum to remove trapped air and volatiles. This segmentation of the vacuum function into two independent systems allows both compaction and volatile removal to be optimized without compromising either function.
Solution Approach 2:
The curing process uses periodic or sequential vacuum application in two stages. First, the inner bag is collapsed with high vacuum pressure to compact the composite. Then, the outer bag applies vacuum pressure to remove trapped air and volatiles that may have been trapped during compaction. This periodic action ensures both compaction and thorough volatile removal are achieved at different stages of the curing cycle.
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 configuration allows for efficient removal of trapped air and volatiles without compromising sealing integrity, enabling void-free composite curing suitable for both manufacturing and repair processes without the need for external pressure sources like autoclaves.
Implementation Method 1
vacuum pressure is applied both to the inner vacuum bag and to the outer vacuum bag with a slightly higher vacuum pressure in the outer vacuum bag than in the inner vacuum bag
Implementation Method 2
incorporating a heating source for controlled curing
Data Source
AI summary
A system for curing polymer matrix composite parts out of autoclave in manufacturing and repairing processes including: (i) an inner vacuum bag (3) placed over the lay-up to be cured located over a working area (15, 18) with the edges of the inner vacuum bag (3) joined to the working area by first sealing elements (8); (ii) a Perforated bulkhead (4) located over the inner vacuum bag (3), (iii) an Outer vacuum bag (2) over a perforated bulkhead (4) and over the edges of the inner vacuum bag with the edges of the outer vacuum bag (2) joined to the working area (15, 18) by second sealing elements (1), (iv) a vacuum device (5, 7, 6) and (v) a heating source (9, 20).