Composite Hole Plug Structure for Vacuum-Assisted Repair
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Solution Overview
Problem
The challenge in repairing composite structures, such as carbon fiber reinforced polymers, lies in accessing the backside of the repair surface due to hollow areas or gaps, which impedes the establishment of a vacuum force during the cure process, potentially leading to lifting of the repair patch.
Innovation Solution
A hole plug with a flange, bevel, shank, and nubs is designed to fill the opening through the carbon composite, providing a secure interface for adhesive bonding and vacuum application, ensuring proper debulking of repair layers and preventing the patch from lifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hole plug is inserted to fill the opening through the carbon composite, then vacuum force can be applied effectively during curing, but the hole plug structure itself occupies space in the hollow area
Solution Approach 1:
The hole plug is segmented into multiple functional components: a flange portion for vacuum application, a shank portion for structural support, and multiple nubs for mechanical interlocking with the carbon composite layers. This segmentation allows each component to perform its specific function while minimizing overall space occupation.
Solution Approach 2:
The hole plug is designed to nest within the hollow area created by removing the damaged section. The flange sits at the first surface, the shank extends through the hollow area, and the nubs engage with the carbon composite layers, effectively nesting the repair structure within the existing geometry without requiring additional external space.
2Strength
If the hole plug includes multiple nubs and grooves for mechanical interlocking, then bonding strength is improved, but manufacturing complexity increases
Solution Approach 1:
The hole plug incorporates a porous or textured surface structure with multiple grooves and nubs that increase the surface area and mechanical interlocking capability. This porous-like structure enhances bonding strength by providing multiple engagement points with the carbon composite layers while being manufacturable through standard processes.
Solution Approach 2:
The hole plug is designed as a composite structure combining different geometric features (flange, shank, nubs, grooves) that work together to provide both mechanical strength and bonding capability. The integration of these features into a single monolithic component maintains manufacturing simplicity while achieving superior bonding performance.
3Ease of operation
If the hole plug is designed with a flange at the first surface, then vacuum application is enabled, but the flange diameter increases the overall size
Solution Approach 1:
The flange of the hole plug serves multiple functions: it provides a surface for vacuum application, acts as a structural support element, and helps distribute loads across the repair area. By making the flange multi-functional, the design achieves vacuum application capability without requiring an excessively large diameter, as the same structure performs multiple roles.
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 hole plug facilitates effective adhesive bonding and vacuum debulking, ensuring a robust and reliable repair process by maintaining the patch in place during curing and preventing air leakage, thus enhancing the structural integrity of the composite assembly.
Implementation Method 1
providing a secure interface for adhesive bonding
Implementation Method 2
a vacuum force is applied to the fiber patch during the resin cure to compact the two or more fiber layers that make up the fiber patch by removing air and volatile gases from within and between the laminated layers
Data Source
AI summary
A hole plug that can be used during rework or repair of a composite fiber assembly includes various features that allow placement of a vacuum force to the surface being reworked or repaired. In some implementations, the hole plug can include a plurality of nubs positioned around a shank. The nubs can secure the hole plug to the composite fiber assembly until a cure of an adhesive. The hole plug can further include a plurality of longitudinally oriented grooves extending along the shank and positioned between the plurality of nubs, and can include a notch positioned circumferentially around the shank. The grooves and notch can be used as adhesive carriers that assist with dispersal of a sufficient volume of the adhesive onto other portions of the shank and the composite fiber assembly during insertion of the hole plug into a hole in the composite fiber assembly.