Embedded Connecting Element for Flush Sandwich Structure Fastening
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Solution Overview
Problem
In sandwich structures used in lightweight construction, particularly in the aviation sector, insert pulls occur due to the deformation of one cover layer when a screw is tightened, leading to a complex and cost-intensive revarnishing process to address visible light reflection issues, and replacing the core with a rigid filling material increases weight and production complexity.
Innovation Solution
A connecting element with an insert embedded in the sandwich structure is finished flush with the cover layer or protrudes from it by a predetermined height, preventing relative movement and deformation, which can be achieved by blending or using a compensating element like a knifing filler or prefabricated washer to ensure the insert is securely embedded without damaging the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the core is replaced with rigid filling material in insert regions, then insert pulls are prevented, but weight increases and production complexity increases
Solution Approach 1:
The patent applies local reinforcement by providing a reinforcing element only in the region of the blind hole, rather than replacing the entire core with rigid filling material. The reinforcing element has a local bonding area that bonds to the core only in the blind hole region, providing localized support to prevent insert pulls while maintaining the lightweight properties of the rest of the sandwich structure.
Solution Approach 2:
The solution segments the core reinforcement into a localized reinforcing element rather than using a continuous rigid filling material throughout the core. This segmented approach allows the reinforcing element to provide targeted support where needed (at the blind hole location) while leaving the rest of the core structure intact and lightweight.
2Strength
If the insert is embedded deeply into the sandwich structure, then connection strength is improved, but insert pulls occur due to cover layer deformation
Solution Approach 1:
The reinforcing element provides localized reinforcement at the blind hole region, allowing the insert to be embedded with sufficient depth for strong connection while the reinforcing element prevents excessive deformation of the cover layer that would cause insert pulls and surface defects.
Data Source
AI summary
A sandwich structure includes two cover layers and a core arranged therebetween, and at least one connecting element for connection to further components. The connecting element has an insert, which is embedded into the sandwich structure at a cover layer of the two cover layers. An embedding depth of the insert is less than a thickness of the core. The connecting element is finished flush with an outer side of the cover layer via which the connecting element is embedded or protrudes from the cover layer.