Composite Rework Patch with Fracture Zones
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Solution Overview
Problem
Existing methods for reworking composite structures, such as those in aircraft, often require mechanical fasteners, which increase weight and drag, and make it difficult to monitor changes in bonded joints over time, necessitating a solution that allows visual inspection and prediction of bond joint changes.
Innovation Solution
A composite rework patch with multiple regions of differing fracture toughness, including a first disbond control region, a second disbond control region, and a separation zone with higher fracture toughness, allowing for visual inspection and prediction of bond joint changes by controlling the advancement of disbond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If mechanical fasteners are used to secure the rework patch, then the patch can be securely attached to the structure, but the aircraft weight and drag increase
Solution Approach 1:
The patent replaces mechanical fastening systems with a bonded joint system using adhesive. The rework patch is secured to the parent structure through chemical bonding rather than mechanical fasteners, eliminating the weight and drag penalties associated with fasteners while maintaining secure attachment. The bonded joint creates a continuous load path across the patch-structure interface.
Solution Approach 2:
The patent changes the attachment mechanism from mechanical (fasteners) to chemical (adhesive bonding). This parameter change in the attachment method eliminates the need for physical fastening elements, thereby reducing aircraft weight and aerodynamic drag while providing sufficient attachment strength through the bonded joint.
2Strength
If mechanical fasteners are used to secure the rework patch, then the patch can be securely attached to the structure, but the aesthetic appearance deteriorates
Solution Approach 1:
The patent replaces mechanical fastening systems with a bonded joint system using adhesive. The rework patch is secured to the parent structure through chemical bonding rather than mechanical fasteners, eliminating the weight and drag penalties associated with fasteners while maintaining secure attachment. The bonded joint creates a continuous load path across the patch-structure interface.
3Weight of moving object
If a bonded joint is used to secure the rework patch, then aircraft weight and drag are reduced, but the condition of the bond joint cannot be easily monitored over time
Solution Approach 1:
The patent divides the bonded rework patch into multiple zones with different fracture toughness characteristics. This segmentation creates distinct regions that will fail in a predictable sequence, allowing the condition of the bond joint to be monitored by observing which zone shows signs of distress or failure. The segmented design transforms an invisible bonding process into a visible, monitorable system.
Solution Approach 2:
The patent incorporates visual indicators that change color or appearance based on the condition of the bond joint. These indicators are embedded in the patch or adhesive system and provide visual feedback about the health of the bonded connection, enabling easy monitoring without requiring complex inspection equipment or disassembly.
4Loss of energy
If a bonded joint is used to secure the rework patch, then aircraft weight and drag are reduced, but the ability to monitor bond joint changes deteriorates
Solution Approach 1:
The patent divides the bonded rework patch into multiple zones with different fracture toughness characteristics. This segmentation creates distinct regions that will fail in a predictable sequence, allowing the condition of the bond joint to be monitored by observing which zone shows signs of distress or failure. The segmented design transforms an invisible bonding process into a visible, monitorable system.
Solution Approach 2:
The patent incorporates visual indicators that change color or appearance based on the condition of the bond joint. These indicators are embedded in the patch or adhesive system and provide visual feedback about the health of the bonded connection, enabling easy monitoring without requiring complex inspection equipment or disassembly.
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
Enables reliable visual monitoring and prediction of bond joint changes, facilitating certification and reducing the need for mechanical fasteners, while effectively controlling the advancement of disbond in composite structures.
Implementation Method 1
The separation zone has a fracture toughness greater than the fracture toughness of the first control region
Data Source
AI summary
A composite laminate patch for reworking an inconsistent area in a structure has inner and outer control regions possessing differing interlaminar fracture toughnesses for controlling the advance of a disbond in the patch. One or more separation zones in the patch between the control regions aids in diffusing the fracture energy of the disbond as the disbond advances from the inner region to the outer region.