Skin-Bonded Threaded Inserts for Adhesive-Free Sandwich Panels
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Solution Overview
Problem
Conventional round inserts in sandwich panels require labor-intensive adhesive application and curing, leading to inefficiencies and defects such as shifting and imperfect positioning, which hinder automation and increase the risk of bond failure.
Innovation Solution
Skin-bonded threaded inserts that rely on friction fit with the panel skins for stability, eliminating the need for adhesive and allowing concurrent curing with the panel, using a collar that transitions between raised and compressed positions during installation to ensure secure engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adhesive material is used to secure the insert in place, then the insert is retained within the sandwich panel, but the process becomes labor-intensive and time-consuming with curing time of 2-6 hours or more
Solution Approach 1:
The patent removes the adhesive material from the insertion process, extracting the problematic curing step entirely. The insert is retained through mechanical interference fit between the insert body and the bore, eliminating the need for adhesive bonding and its associated labor-intensive application and long curing time.
Solution Approach 2:
The patent replaces the chemical bonding system (adhesive) with a mechanical retention system. The insert features a body with external dimensions that create friction fit and mechanical interference with the bore walls, providing retention through physical contact and friction rather than chemical adhesion.
2Reliability
If adhesive material is used to bond the insert, then the insert is secured in place, but the insert may shift during curing and positioning becomes imperfect
Solution Approach 1:
The insert is designed with pre-configured geometric features including a body with specific external dimensions and a flange that engage with the bore and panel skin before any curing process. The mechanical interference fit is established immediately upon insertion, preventing any shifting or movement during what would traditionally be the curing period.
Solution Approach 2:
By removing the adhesive curing process entirely, the patent eliminates the time window during which shifting could occur. The mechanical retention system provides immediate and continuous positioning stability from insertion through final assembly, with no intermediate vulnerable state.
3Reliability
If adhesive compound is injected through potting holes, then the insert is retained, but excess adhesive must be removed and the process is labor-intensive
Solution Approach 1:
The patent eliminates the adhesive application step entirely, removing potting holes, adhesive injection equipment, and post-application cleanup operations. The mechanical interference fit requires no additional materials or steps beyond inserting the pre-formed insert into the prepared bore.
Solution Approach 2:
The insert design incorporates self-retaining features where the body dimensions and flange geometry automatically create the necessary retention and positioning when inserted into the bore. The system is self-sufficient, requiring no external adhesive application or specialized tooling beyond standard insertion equipment.
4Productivity
If the insert is installed without adhesive, then manufacturing efficiency is improved, but the insert may not be securely retained
Solution Approach 1:
The patent modifies the geometric parameters of the insert body, specifically the external dimensions and surface characteristics, to create optimal friction fit and mechanical interference with the bore. The body is designed with specific diameter, length, and surface roughness parameters that generate sufficient friction and normal force to retain the insert securely without adhesive.
Solution Approach 2:
The retention mechanism combines multiple physical phenomena: friction between the insert body and bore walls, normal force from mechanical interference fit, and potentially deformation of the panel skin or core material around the insert. This composite retention mechanism provides reliable holding strength through the combination of these effects rather than relying on a single mechanism.
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 solution enhances manufacturing efficiency by reducing processing steps, improving flushness, and increasing the strength and reliability of the insert installation, while avoiding the limitations of adhesive-based bonding.
Implementation Method 1
a collar that is sized with respect to the first enlarged portion of the hole such that an external surface of the collar has a friction fit with the first enlarged portion
Data Source
AI summary
Skin-bonded threaded inserts may be installed within a sandwich panel by curing the insert in place as the sandwich panel is cured. Skin-bonded threaded inserts may include a collar that is transitioned between a raised position and a compressed position during installation of the skin-bonded threaded insert in the sandwich panel, due to compression of the sandwich panel during curing. Skin-bonded threaded inserts may include one or more flanges that engage one or more skins of the sandwich panel. Such flanges may be positioned between two skins, or between the core and a skin of the sandwich panel to secure the sandwich panel in place within the sandwich panel. Skin-bonded threaded inserts may be positioned within a sandwich panel without the use of potting compound and may engage with the skins of the sandwich panel, rather than relying on adherence to the core for sufficient pull-out and shear strength.