Dielectric Nut Retainer Strip for Lightning-Isolated Wing Fasteners
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Solution Overview
Problem
Aerospace vehicle manufacturers face challenges in providing lightning protection for composite components, particularly on thin wings where metal fasteners need to be electrically isolated to prevent ignition hazards, while also being removable for maintenance and inspections without adding weight or complexity.
Innovation Solution
The use of a dielectric nut retainer strip made of dielectric material, which includes fastener thru holes, cap receiver portions, anti-rotation nut retainer portions, and a substructure fastener portion, along with a conductive coating on fasteners, to create a fastening system that isolates fasteners electrically while allowing for easy removal and reinstallation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal fasteners are used to connect composite aerospace vehicle components, then structural strength and connection reliability are improved, but electrical isolation is lost creating ignition hazards from lightning
Solution Approach 1:
A dielectric nut retainer strip is introduced as an intermediary component between the metal fastener and the composite structure. This strip provides both mechanical retention (maintaining structural connection) and electrical isolation (preventing lightning ignition hazards). The dielectric material blocks electrical current while the mechanical features (through holes, retention features) maintain fastener connection.
Solution Approach 2:
The solution uses composite construction by combining dielectric material with mechanical fastening features. The dielectric nut retainer strip integrates multiple functions (electrical isolation, mechanical retention, fastener positioning) into a single composite component that bridges the gap between metal fastener and composite structure.
2Ease of repair
If access panels are added to allow inspection and removal of fasteners, then ease of maintenance is improved, but weight and drag of the wing structure increase
Solution Approach 1:
The dielectric nut retainer strip includes integrally formed cap receiver portions that accept caps to protect fasteners, and the entire assembly is designed to be removable as a unit. The fastener can be accessed by removing the cap and retainer strip from the exterior, allowing maintenance without additional access panels. The structure serves its own maintenance needs through its inherent design.
3Ease of manufacture
If fasteners are inserted from accessible side to connect inaccessible parts, then ease of installation is improved, but removability is lost requiring destruction of fastener
Solution Approach 1:
The fastening system is segmented into distinct functional components: the dielectric nut retainer strip (providing retention and electrical isolation), the cap (protecting the fastener), and the metal fastener itself. This segmentation allows the fastener to be inserted from the accessible side while the retainer strip and cap remain on the accessible side for easy removal and reinstallation without destroying any component.
4Object-affected harmful factors
If dielectric materials are used to isolate fasteners electrically, then lightning protection is improved, but fastener removal and reinstallation becomes difficult
Solution Approach 1:
The dielectric nut retainer strip performs multiple functions simultaneously: it provides electrical isolation (lightning protection), mechanical retention of the fastener, positioning alignment through through holes, and structural support. By integrating these functions into a single multi-functional component, the system achieves lightning protection without compromising fastener removability and reinstallation ease.
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 effectively isolates fasteners electrically, preventing ignition hazards from lightning, while allowing for easy removal and reinstallation without adding weight or complexity to the aerospace vehicle structure.
Implementation Method 1
a dielectric nut retainer strip formed of dielectric material having at least one fastener thru hole
Data Source
AI summary
A method for assembling an aerospace vehicle wing, the method includes inserting at least one nut in at least one nut retention pocket formed on a dielectric nut retainer strip, attaching the dielectric nut retainer strip to a wing substructure over a fastener hole, applying at least one cap to the dielectric nut retainer strip over the at least one nut in the at least one nut retention pocket, locating a wing skin over the fastener hole, inserting a fastener through the wing skin into the fastener hole, and fastening the fastener to the at least one nut.