Perforated Patch Bond Line Control
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Solution Overview
Problem
Current adhesive bonding processes in the aircraft industry face challenges in achieving consistent bond line thickness and reducing porosity, making it difficult to bond patches to structures effectively, especially in field applications where specialized equipment and skilled technicians are not available.
Innovation Solution
The method involves creating perforations in the patch to allow air and excess adhesive to escape, using a spacer like a screen or beads to control adhesive thickness, and applying pressure through a caul plate limited by an anti-caul plate to ensure uniform pressure distribution, allowing for quick and repeatable bonding in the field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pressure is applied to the patch during bonding to control bond line thickness, then bond line thickness control is improved, but porosity due to air pockets may increase
Solution Approach 1:
The patch is designed with a porous structure containing multiple channels that allow air and volatiles to escape during the bonding process. This porous design enables pressure to be applied for bond line thickness control while simultaneously providing pathways for air evacuation, thus preventing porosity in the adhesive bond.
2Manufacturing precision
If film type adhesives of constant thickness are used to control bond line thickness, then bond line thickness control is improved, but handling complexity increases due to refrigeration requirements
Solution Approach 1:
The invention uses a disposable porous patch with integrated channels instead of reusable film adhesives. This eliminates the need for refrigeration and special handling of film adhesives, while still providing consistent bond line thickness control through the porous structure that maintains adhesive distribution.
3Manufacturing precision
If pressure is applied uniformly across the patch to achieve desired bond line thickness, then bond consistency is improved, but applying exact pressure uniformly is difficult
Solution Approach 1:
The patch features locally varied properties with channels distributed across different regions. This local quality variation allows the patch to accommodate pressure variations and guide adhesive flow to achieve uniform bond line thickness even when pressure application is not perfectly uniform, reducing the skill level required for consistent results.
4Adaptability or versatility
If the bonding process is performed in the field without specialized equipment, then field applicability is improved, but bond line thickness control and porosity reduction become more difficult
Solution Approach 1:
The porous patch with integrated channels performs self-service functions by automatically guiding adhesive flow and evacuating air during bonding. This self-regulating mechanism enables field applicability without specialized equipment while maintaining bond line thickness control and minimizing porosity through the inherent design of the porous structure.
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 close control of bond line thickness and reduces porosity, resulting in consistent and repeatable adhesive bonds that can be achieved by non-skilled technicians in field conditions, improving the efficiency and reliability of patch bonding.
Implementation Method 1
The spacer may comprise a screen and/or a plurality of beads that maintain a desired spacing between the patch and the structure
Implementation Method 2
The perforations in the patch allow air and excess adhesive to escape from the patch as the patch is being pressed against the structure
Implementation Method 3
The patch is pressed against the structure to achieve a desired bond line thickness
Data Source
AI summary
A patch may be used to rework a composite structure in the field. The patch is bonded to the structure by a layer of adhesive and includes perforations that allow the escape of air from the adhesive as the patch is compressed against the structure. A spacer may be introduced between the patch and the structure to control the thickness of the adhesive layer.