Tapered Adhesive Patch for Composite Rework
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Solution Overview
Problem
Existing methods for reworking inconsistent areas in composite structures, such as those in aircraft, often result in increased weight and drag due to the use of fasteners or fail to effectively reduce the spread of inconsistencies, particularly cracks and delamination, leading to suboptimal damage tolerance and durability.
Innovation Solution
A method and apparatus utilizing a patch with tapered adhesive sections, where the adhesive sections have varying structural properties to efficiently reduce strain energy release rates, thereby reducing the propagation of cracks and enhancing the damage tolerance and durability of the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If fasteners are used to secure the patch, then the patch can be mechanically attached to the structure, but the aircraft weight and drag increase
Solution Approach 1:
The patent replaces the mechanical fastening system with a bonded joint system using adhesive layers. The patch is attached to the parent structure through adhesive bonds rather than mechanical fasteners, eliminating the weight and drag penalties associated with fasteners while maintaining structural integrity through chemical bonding.
Solution Approach 2:
The patent employs tapered adhesive sections where the adhesive thickness varies spatially, being thickest at the edges and thinnest at the center. This parameter change in adhesive geometry optimizes the bond joint to provide adequate strength while minimizing weight, and also helps control stress distribution to prevent inconsistency spread.
2Strength
If a bonded patch is used without tapered adhesive sections, then the patch can be attached to the structure, but the inconsistency spread is not reduced effectively
Solution Approach 1:
The patent applies different adhesive thicknesses to different locations of the bond joint. The tapered adhesive sections create local variations in adhesive geometry, with thicker adhesive at edges and thinner adhesive at the center. This local quality differentiation allows the bond joint to simultaneously provide strong attachment and有效控制 inconsistency spread by controlling stress distribution patterns.
Solution Approach 2:
The patent changes the geometric parameters of the adhesive layer by introducing tapered sections with varying thickness. This parameter change transforms the uniform adhesive joint into a non-uniform joint that can control stress flow and energy release rates, thereby improving damage tolerance and preventing inconsistency propagation while maintaining bond strength.
3Ease of manufacture
If uniform adhesive thickness is used, then the bonding process is simpler, but the strain energy release rate is not reduced efficiently
Solution Approach 1:
The patent introduces parameter changes in the adhesive thickness to optimize strain energy release rate control. The tapered adhesive sections with varying thickness create a gradient that efficiently manages stress distribution and energy release, preventing inconsistency spread. While this increases manufacturing complexity compared to uniform adhesive, it provides superior structural reliability and damage tolerance.
Data Source
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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.