Composite Core Repair Using Photopolymer Lattice Structures
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Solution Overview
Problem
Existing repair methods for composite sandwich structures fail to effectively restore the load-carrying capability of damaged panels, as they lack efficient load transfer between the repair and original core sections, leading to reduced strength compared to undamaged panels.
Innovation Solution
The method involves removing damaged sections, forming a cavity, and filling it with photomonomer resin that is exposed to collimated light through a mask to create a three-dimensional truss or lattice structure within the core, which interpenetrates to form a continuous material, allowing for structural connection to the original core and facesheets, thereby enhancing load transfer and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional repair methods are used to fill damaged core sections, then the repair process is simple, but the load-carrying capability is not effectively restored due to poor load transfer between repair and original core sections
Solution Approach 1:
The patent uses a dual-material system combining photopolymer resin (for waveguide formation) and silicone rubber (for bulk filling). The photopolymer forms a lattice structure with high load-bearing capacity through photopolymerization, while the silicone rubber provides structural continuity. This composite approach restores load-carrying capability by creating distinct functional zones within the repair material.
Solution Approach 2:
The repair method applies different material properties to different regions: the photopolymer resin creates a structured lattice in load-critical areas where load transfer is needed, while the silicone rubber fills remaining spaces for structural completion. This localized differentiation of material quality enables effective load transfer at the interface between repair and original core sections.
2Strength
If a lattice structure is formed using photopolymer resin and collimated light, then load transfer is significantly improved, but the repair process becomes more complex and time-consuming
Solution Approach 1:
The patent applies collimated light only partially - specifically targeted at the photopolymer resin regions where lattice structure formation is needed for load transfer, rather than illuminating the entire repair area uniformly. This selective photopolymerization achieves the necessary structural reinforcement while minimizing unnecessary processing time and energy expenditure.
Solution Approach 2:
The repair process is segmented into distinct phases: first forming the photopolymer lattice structure through controlled photopolymerization in load-critical zones, then filling remaining spaces with silicone rubber. This segmentation allows the time-consuming photopolymerization to be confined to only the necessary regions, improving overall repair productivity.
3Strength
If the cavity is completely filled with photopolymer resin to form a continuous lattice structure, then structural connection is maximized, but material cost and processing time increase
Solution Approach 1:
The patent applies photopolymer resin specifically in regions where structural connection and load transfer are critical - primarily at the interface between the repair section and the original core, and in load-bearing pathways. The silicone rubber complements this by filling non-critical spaces, reducing the total quantity of photopolymer resin needed while maintaining structural integrity.
Solution Approach 2:
By combining photopolymer resin with silicone rubber in a composite repair material system, the patent achieves continuous structural connection without requiring complete filling with the more expensive and slower-curing photopolymer. The two materials work together to provide both structural continuity and load transfer capability.
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 significantly improves the load-carrying capability of the repaired panel, often exceeding that of the damaged panel and approaching the strength of the undamaged panel, by forming a structurally connected repair section that enables efficient shear load transfer.
Implementation Method 1
The cavity is at least partially filled with a photomonomer resin, which then is illuminated through a mask with collimated light to form a cellular structure in the cavity
Data Source
AI summary
A method for repairing a composite structure. A damaged portion of a first facesheet of the structure is removed, forming a hole in the first facesheet. A damaged portion of the underlying core is removed to form a cavity in the sandwich. If the second facesheet is damaged, the damaged section is removed, and covered and sealed with a facesheet repair section. If the core material is an open-cell material, a dam is formed around the perimeter of the cavity, to act as a barrier between the cavity and the core material. The cavity is at least partially filled with a photomonomer resin, which then is illuminated through a mask with collimated light to form a truss structure in the cavity. Residual photomonomer resin is removed, and a facesheet repair section is bonded over the hole in the first facesheet.