Composite Hole Plug Structure for Vacuum-Assisted Repair Bonding
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Solution Overview
Problem
The repair of composite structures, such as carbon fiber reinforced polymers, is challenging due to the difficulty in establishing a vacuum force during the curing process, especially when the structure has a hollow area or gap that prevents access to the back side, leading to issues like the repair patch lifting away from the surface.
Innovation Solution
A hole plug with a flange, bevel, shank, and nubs is used to fill the opening through the carbon composite, providing a structure for adhesive bonding and vacuum application, ensuring the repair patch adheres properly and maintaining the integrity of the composite structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a hollow area or gap is present in the composite structure during repair, then access to the back side is prevented, but vacuum force establishment becomes difficult
Solution Approach 1:
A hole plug is introduced as an intermediary component to bridge the gap between the skin and composite laminate. The hole plug includes a flange that contacts the skin, a shank that extends into the hollow area, and a tip that contacts the composite laminate, thereby transmitting vacuum force through the hollow area to enable effective debulking of repair layers.
Solution Approach 2:
The hole plug extends in the thickness direction (z-dimension) of the composite structure, bridging the hollow area that prevents vacuum force transmission. By adding this dimensional element, the vacuum force can be transmitted from the skin surface through the hollow area to the composite laminate, enabling effective repair.
2Productivity
If the repair patch is applied without proper vacuum force, then the repair process can be completed, but the repair patch lifts away from the surface
Solution Approach 1:
The hole plug acts as a mediator to transmit vacuum force through the hollow area, enabling the vacuum to hold the repair patch firmly against the surface during curing. This prevents the repair patch from lifting away while maintaining structural integrity.
3Reliability
If the hole plug includes engagement features like nubs and grooves, then adhesive bonding is improved, but manufacturing complexity increases
Solution Approach 1:
The hole plug incorporates a porous or textured surface structure with nubs and grooves that increase the surface area and mechanical interlocking capability with the adhesive. This improves adhesive bonding reliability while the overall structure remains relatively simple.
Solution Approach 2:
The engagement features (nubs and grooves) are localized to specific regions of the hole plug, particularly at the interface with the adhesive and repair layers. This provides enhanced bonding where needed without unnecessarily complicating the entire structure.
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 simplifies the repair process by allowing effective adhesive bonding and vacuum debulking of repair layers, ensuring a strong and reliable repair of composite structures while maintaining structural integrity.
Implementation Method 1
a vacuum force can be applied to the composite fiber assembly to debulk the one or more repair layers
Implementation Method 2
applying an adhesive to a plurality of grooves defined by a shank of a hole plug
Data Source
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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.