Integral Double Bag for Vacuum Composite Bagging
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Solution Overview
Problem
The existing method of double bagging composite parts for vacuum bagging is time-consuming and requires excessive material, particularly due to the need for separate formation, trimming, and sealing of inner and outer bags, which can lead to tooling issues with increased weight and longer cure cycles.
Innovation Solution
An integral double bag system where inner and outer bags are pre-aligned and attached at spaced apart locations using bonding techniques like ultrasonic welding or heat sealing, allowing for a single, pre-assembled bag assembly that can be quickly aligned and sealed over the composite part, reducing the need for extensive tool base area and material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate inner and outer bags are used for double bagging, then vacuum seal integrity is improved, but setup time and material usage increase
Solution Approach 1:
The patent combines the inner and outer bags into a single integrated double-bag structure where the outer bag is formed with an extended flange that overlaps and is sealed to the tool base, eliminating the need for separate bag installation steps while maintaining the protective function of double bagging
2Reliability
If separate inner and outer bags are used for double bagging, then vacuum seal integrity is improved, but material requirements increase
Solution Approach 1:
The integrated double-bag design uses a single continuous material structure where the outer bag's extended flange serves both as the outer containment and the sealing surface, reducing the total material required compared to two separate bags that would both require full sealing margins
3Ease of manufacture
If larger tool surface area is used to accommodate separate bag sealing, then bag sealing capability is improved, but tool weight increases
Solution Approach 1:
The invention extends the sealing area in the vertical dimension by creating an extended flange on the outer bag that hangs down and seals to the tool base, allowing adequate sealing area without increasing the horizontal footprint or tool weight
4Ease of manufacture
If larger tool surface area is used to accommodate separate bag sealing, then bag sealing capability is improved, but cure cycle time increases
Solution Approach 1:
By extending the flange vertically rather than increasing the horizontal tool surface area, the design provides adequate sealing capability without increasing the tool's thermal mass, thus maintaining the original cure cycle time
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 setup time and material requirements, allowing for faster alignment and sealing of the double bag assembly, resulting in shorter cure cycles and lighter tooling with reduced thermal mass, while maintaining the integrity of the vacuum compaction process.
Implementation Method 1
drawing a vacuum in the inner and outer bags to compact part
Implementation Method 2
Heat is simultaneously applied to the lay-up by placing the bagged part in an oven or autoclave
Data Source
AI summary
Composite parts such as plastic laminates are formed using a pre-assembled, integral double bag to vacuum bag the part. The double bag is formed of two sheets of bag material that are cut to pre-determined width dimensions, with the width of one sheet being less than that of the other. The bag sheets are prealigned and then attached to each other by spaced apart bonds between the sheets which hold the bag sheets in registered relationship to each other when the double bag is placed over the part and sealed to a tool base. The attachment bonds may be formed by ultrasonic welding, heat sealing or an adhesive.