Vacuum-Assisted Bond Cavity Joining for Void-Free Bondlines
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Solution Overview
Problem
Current bonding methods for large or complex structures, such as aircraft components, often result in bondlines with voids and strength variations, leading to lower performance capabilities and higher costs.
Innovation Solution
A method involving the formation of a bond cavity between two structures, placement of a semi-permeable breather material, and a vacuum bag, followed by evacuation and injection of de-aerated adhesive while curing with heaters to create a void-free bondline.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If adhesive injection approaches are used to create bondlines between bonded members, then the bonding process can be simplified, but voids and variation in strength are created in the bondlines
Solution Approach 1:
The patent applies vacuum evacuation to create a vacuum environment within the bond cavity during adhesive injection. This vacuum environment removes air and volatiles from the adhesive and bondline, preventing void formation while maintaining process simplicity. The vacuum bag and evacuation system create an inert atmosphere that eliminates harmful gases without complicating the manufacturing process.
Solution Approach 2:
The patent uses a breather material with controlled porosity placed at the adhesive injection port. This porous material allows air and volatiles to escape during vacuum evacuation while preventing adhesive from leaking out. The breather material's selective permeability enables void-free bondline creation while maintaining simple adhesive injection methodology.
2Productivity
If conventional bonding methods are used for large or complex structures, then the process can be completed, but the bondlines contain voids and strength variations leading to lower performance
Solution Approach 1:
The vacuum evacuation system creates a consistent vacuum environment throughout the entire bonding process for large or complex structures. This inert vacuum atmosphere ensures uniform void removal from all areas of the bondline, including hard-to-reach regions, thereby maintaining productivity while significantly improving reliability and strength consistency across the entire bonded structure.
Solution Approach 2:
The patent changes the pressure parameter by evacuating the bond cavity to vacuum conditions during adhesive injection. This parameter change from atmospheric pressure to vacuum pressure fundamentally alters the bonding process, enabling complete void removal and consistent adhesive distribution throughout the bondline, thereby improving both productivity and reliability simultaneously.
3Ease of manufacture
If paste bonds with adhesive injection are used in aircraft joints, then the bonding can be achieved, but voids and strength variation result in lower performance capability
Solution Approach 1:
The vacuum evacuation system creates an inert vacuum atmosphere during adhesive injection into aircraft joints. This vacuum environment removes air bubbles and volatiles from the paste adhesive, ensuring complete wetting and void-free bonding. The method maintains ease of manufacture through simple adhesive injection while dramatically improving joint strength and performance capability by eliminating voids.
Solution Approach 2:
The breather material with controlled porosity is positioned at the injection port to allow air and volatiles to escape during vacuum evacuation while blocking adhesive leakage. This porous material enables the simultaneous achievement of easy adhesive injection and high joint strength by facilitating complete void removal while maintaining simple manufacturing procedures.
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 enables the creation of high-quality, void-free bondlines with improved strength and reduced cost, addressing the limitations of existing methods by ensuring a consistent and strong bond.
Implementation Method 1
evacuating the bond cavity via a vacuum port and forcing adhesive into the bond cavity via an adhesive port while the bond cavity is evacuated
Implementation Method 2
evacuating the bond cavity via a vacuum port and forcing adhesive into the bond cavity via an adhesive port while the bond cavity is evacuated
Implementation Method 3
placing a semi-permeable breather material at one or more exits of the bond cavity
Implementation Method 4
curing the adhesive via one or more heaters to bond the first structure to the second structure
Data Source
AI summary
An example method of joining a first structure and a second structure is described that includes forming a bond cavity between a first structure and a second structure, placing a semi-permeable breather material at one or more exits of the bond cavity, placing a vacuum bag around the bond cavity and the semi-permeable breather material, evacuating the bond cavity via a vacuum port and forcing adhesive into the bond cavity via an adhesive port while the bond cavity is evacuated, and curing the adhesive via one or more heaters to bond the first structure to the second structure.