Double Vacuum Debulk Protocol for Carbon-Epoxy Laminates
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Solution Overview
Problem
Existing vacuum bag processing techniques for composite prepreg materials, such as Torayca 3631 carbon-epoxy prepreg, result in excessively long processing times and high porosity levels, especially when dealing with thick patches or reworks, which limits the ability to achieve desired strength and integrity in composite structures.
Innovation Solution
A protocol for determining process parameters using double vacuum debulk (DVD) techniques, including rheology studies, trial panels with varying time/temperature profiles, and non-destructive inspections to optimize consolidation and reduce porosity, allowing for efficient fabrication of thick composite patches with improved quality and reduced processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If vacuum bag processing is used for thick composite patches, then processing time is reduced, but porosity levels increase excessively
Solution Approach 1:
The vacuum bag processing is divided into two distinct stages: a debulking stage at atmospheric pressure to remove air pockets, followed by a curing stage at vacuum pressure to consolidate the laminate. This segmentation allows each stage to optimize for its specific function, reducing overall porosity while maintaining efficient processing time.
Solution Approach 2:
The process employs periodic action by alternating between debulking and curing phases with specific timing sequences. The debulking phase removes trapped air, followed by the curing phase that consolidates the material, creating a periodic cycle that achieves both low porosity and efficient processing.
2Strength
If multiple adhesive layers are applied to thick patches, then structural strength is improved, but porosity in adhesive layers increases
Solution Approach 1:
The debulking action is performed preliminarily before the adhesive layers are fully cured. By removing air pockets and consolidating the laminate structure in advance, the subsequent adhesive application occurs on a pre-consolidated surface, preventing air entrapment within adhesive layers and eliminating the need for multiple thick adhesive applications.
3Device complexity
If standard vacuum bag processing is used for rework patches, then equipment simplicity is maintained, but processing time becomes excessively long
Solution Approach 1:
The process uses periodic action by implementing sequential debulking and curing phases with optimized timing. This allows standard vacuum bag equipment to achieve rapid processing by systematically alternating between air removal and consolidation phases, dramatically reducing total cycle time without requiring complex equipment modifications.
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 DVD protocol significantly reduces processing time and achieves lower porosity levels, enabling the creation of thick, high-strength composite patches that can restore structural integrity, even for complex or reworked structures, without the need for multiple adhesive layers or autoclave processing.
Implementation Method 1
A lower vacuum bag assembly and an upper vacuum bag assembly are used to debulk and cure a multilayer composite material patch
Implementation Method 2
A lower vacuum bag assembly and an upper vacuum bag assembly are used to debulk and cure a multilayer composite material patch
Implementation Method 3
conducting a Non-destructive Inspection (NDI) of at least one panel using 5 MHz through-transmission ultrasonics
Data Source
AI summary
A protocol for determining process parameters for debulking composite laminates is established using a standardized a double vacuum debulk (DVD) process. This allows for the development of a rapid fabrication process for thick laminates of toughened carbon/epoxy composite materials. For rework, a single piece multilayer patch is made available for bonding with an adhesive layer to a prepared structural area.