Tapered Adhesive Patch for Composite Rework
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Solution Overview
Problem
Existing methods for reworking composite structures, such as those in aircraft, often fail to effectively reduce the propagation of inconsistencies like cracks or delamination, and may increase weight or drag due to the use of fasteners, or fail to adequately manage stress concentrations.
Innovation Solution
A composite rework patch with tapered adhesive sections is used, where the patch and adhesive layers are tailored to have different structural properties, reducing strain energy release rates and preventing disbond growth, thereby enhancing damage tolerance and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If mechanical fasteners are used to secure the patch, then the patch can be securely attached to the parent structure, but the aircraft weight and drag increase
Solution Approach 1:
The patent replaces mechanical fasteners with a bonded joint system consisting of a patch and adhesive layers. The adhesive layers are configured with varying thicknesses to create tapered adhesive sections that distribute stresses effectively, providing secure attachment without the weight and drag penalties of mechanical fasteners.
2Weight of moving object
If a bonded patch is used to secure the patch, then weight and drag are reduced, but the spread of inconsistency cannot be limited effectively
Solution Approach 1:
The patent applies local quality by configuring adhesive layers with varying thicknesses in different regions. The adhesive layers are thicker at certain locations and thinner at others, creating tapered adhesive sections that locally control stress distribution and strain energy release rates to limit the spread of inconsistencies.
Solution Approach 2:
The patent changes the geometric parameter of the adhesive layers by varying their thickness through different regions. This creates tapered adhesive sections with different structural properties that control the strain energy release rate and prevent inconsistency propagation while maintaining the benefits of bonded joints.
3Ease of manufacture
If uniform adhesive layers are used, then the bonding process is simple, but stress concentrations are not adequately managed
Solution Approach 1:
The patent applies local quality by configuring adhesive layers with varying thicknesses in different regions. The adhesive layers are thicker at certain locations and thinner at others, creating tapered adhesive sections that locally control stress distribution and strain energy release rates to limit the spread of inconsistencies.
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
The solution effectively reduces the propagation of inconsistencies, increases the lifespan of the patch, and decreases the frequency of rework, while avoiding the weight and drag issues associated with traditional fastener-based methods.
Implementation Method 1
Both the patch regions and the tapered adhesive sections may be tailored to reduce the strain energy release rate at the inconsistent boundary area more efficiently than patches using fasteners or bonded joints without tapered adhesive sections.
Data Source
AI summary
A method and apparatus for reworking a composite structure. A composite rework patch system comprises a composite rework patch and a plurality of adhesive layers. The composite rework patch includes a first side having a contour conforming to an inconsistent area on the composite structure. The composite re patch comprises a plurality of regions having different structural properties. The plurality of adhesive layers is on the first side of the composite rework patch. The plurality of adhesive layers change in thickness within at least one region of the composite rework patch to form tapered adhesive sections.