Composite Preform Consolidation Using Bridge Tool and Pressure Bladder
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Solution Overview
Problem
The processing of large composite materials, such as boat hulls and wind turbine blades, using a single vacuum bag results in high void content due to trapped air and volatiles, which compromises the strength and properties of the composite, as the pressure applied can hinder bubble removal and incomplete consolidation.
Innovation Solution
A method and apparatus utilizing an outer vacuum bag with a hard bridge tool and a pressure bladder to achieve independent control of pressure and vacuum, allowing for pressures higher than traditional vacuum bag processes, facilitating complete consolidation of pre-impregnated preforms by inflating the pressure bladder within the vacuum bag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single vacuum bag is used for curing pre-impregnated materials, then the process is simple and suitable for large parts, but the void content in the composite is too high which negatively affects strength and other properties
Solution Approach 1:
The single vacuum bag system is segmented into multiple independent vacuum chambers (inner vacuum bag and outer vacuum bag) that can operate simultaneously with different pressure levels. This allows one chamber to remove volatiles while another applies consolidation pressure, resolving the contradiction between process simplicity and void content reduction.
Solution Approach 2:
A rigid bridge tool structure serves as an intermediary between the inner and outer vacuum chambers, allowing independent pressure control while maintaining structural stability. The bridge tool enables the outer chamber to apply pressure without directly contacting the preform, thus eliminating voids while the inner chamber continues volatile removal.
2Manufacturing precision
If pressure is applied to the preform inside the vacuum bag to consolidate the laminate, then consolidation is improved, but the pressure actually hinders the removal of bubbles by trapping the bubbles containing air and/or volatiles between the tacky layers of fiber and resin
Solution Approach 1:
The vacuum system is divided into separate chambers with distinct functions: one chamber dedicated to volatile removal and another to consolidation pressure. This temporal and spatial segmentation allows bubble removal to occur before pressure application, preventing bubble trapping while achieving complete consolidation.
Solution Approach 2:
Volatile removal is performed as a preliminary action before consolidation pressure is applied. The first vacuum chamber removes air and volatiles from the preform, and only after this is complete does the second chamber apply pressure for consolidation, ensuring bubbles are eliminated before being trapped.
3Manufacturing precision
If multiple vacuum bags are used to overcome the void content problem, then void removal is improved, but the level of independence achievable is limited and not sufficient for pre-impregnated forms of composites
Solution Approach 1:
The rigid bridge tool acts as a mediator that mechanically connects the outer vacuum chamber to the structure while allowing independent pressure control. This intermediary enables the outer chamber to apply high consolidation pressure without affecting the vacuum level in the inner chamber, achieving the independence needed for pre-impregnated composites.
Solution Approach 2:
The system enables independent control of pressure parameters in different chambers. The inner chamber maintains vacuum (negative pressure) for volatile removal while the outer chamber applies positive pressure for consolidation. This parameter independence allows optimization of each process stage without compromising the other.
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 significantly reduces void content and shortens the processing time, enabling faster and more complete consolidation of composite materials before final shaping and curing, thereby improving the fabricating capacity and reducing the time in expensive molds.
Implementation Method 1
drawing a vacuum in the vacuum bag to remove air and volatiles from the preform
Implementation Method 2
applying pressure to the preform by inflating the pressure bladder to consolidate the preform
Data Source
AI summary
A method of making a composite material article includes, in an exemplary embodiment, providing a pre-impregnated preform formed from a plurality of reinforcing fibers and a polymer matrix, positioning the preform on a flat base plate, positioning a pressure bladder on top of the preform, and positioning a bridge tool above the pressure bladder. The bridge tool includes a top plate and at least one support member. The support members are coupled to the base plate with the top plate spaced above the pressure bladder. The method also includes enclosing the preform and bridge tool inside a vacuum bag by sealingly attaching the vacuum bag to the base plate, drawing a vacuum in the vacuum bag to remove air and volatiles from the preform, and then applying pressure to the preform by inflating the pressure bladder to consolidate the preform.