CFRP Fastener Joint Conductivity via Reflowed Gap Filler
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for enhancing electromagnetic energy (EME) conduction in carbon fiber reinforced plastic (CFRP) structures using metallic fasteners are costly and inefficient, leading to poor current flow and potential hot particle ejection during lightning strikes.
Innovation Solution
Applying a conductive gap filler or coating to the sidewalls of holes in CFRP structures and remelting it post-installation to ensure seamless conductivity, or using a sleeved fastener with conductive coatings, to enhance EME conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metallic fasteners are used to secure CFRP structural elements, then the structural strength and durability are improved, but the electromagnetic energy conduction is worsened due to gaps and discontinuities in the current pathway
Solution Approach 1:
A conductive gap filler material is introduced as an intermediary substance between the metallic fastener and the CFRP structural elements. This filler material fills the gaps and crevices that naturally form during assembly, creating a continuous conductive pathway for electromagnetic energy while maintaining the mechanical fastening function.
Solution Approach 2:
The electrical conductivity parameter of the joint assembly is improved by introducing the conductive gap filler material. The filler material has high electrical conductivity that compensates for the discontinuities created by the mechanical fastening process, thereby improving EME conduction reliability without sacrificing structural strength.
2Ease of manufacture
If conventional drilling methods are used to install fasteners in CFRP, then the manufacturing process is simple, but the EME conduction is worsened due to rough hole surfaces and crevices
Solution Approach 1:
The conductive gap filler acts as a mediator that bridges the discontinuities created by conventional drilling. Rather than requiring complex precision drilling to achieve smooth hole surfaces, the filler material compensates for the rough surfaces and crevices, maintaining EME conduction continuity while preserving manufacturing simplicity.
Solution Approach 2:
The conductive gap filler is applied as a consumable material during assembly. It fills the defects created by conventional drilling and provides the necessary conductive pathway, eliminating the need for expensive precision drilling equipment or complex post-processing operations.
3Reliability
If interference fits are used to improve fastener and carbon fiber contact, then the EME conduction is improved, but the manufacturing cost and complexity increase significantly
Solution Approach 1:
Instead of relying on complex interference fit designs that require precise tolerances and complex assembly procedures, the conductive gap filler serves as a simple intermediary material that is applied to the fastener or hole surface. This approach achieves improved EME conduction through a straightforward application process rather than complex mechanical design.
Solution Approach 2:
The solution changes the approach from modifying mechanical parameters (interference fit tolerances, fastener geometry) to applying a material parameter (conductive filler with specific conductivity and flow properties). This material-based approach simplifies the assembly process while achieving the desired EME conduction improvement.
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 methods significantly reduce voids and discontinuities, improving EME conduction and preventing hot particle ejection by ensuring continuous current pathways.
Implementation Method 1
applying heat to the fastener and the conductive gap filler sufficient to melt and reflow the conductive gap filler
Implementation Method 2
applying heat to the fastener sufficient to remelt and reflow the conductive coating
Implementation Method 3
Methods of enhancing EME conduction in fastening systems... because electric currents travel through structural joints of aircraft, the fasteners must be able to accommodate lightning strikes
Data Source
AI summary
Methods of increasing electromagnetic energy conduction between a fastener and at least two structural elements secured together by the fastener after assembly of the fastener and structural elements, at least one of the structural elements formed as a layer of carbon fiber reinforced plastic. One method includes a) forming a first hole through a first structural element and a second hole through a second structural element, each of the holes being formed to align with the other; b) melting and applying a conductive gap filler to sidewalls of the holes; c) installing a shank portion of the fastener through the first and second holes to complete assembly; and d) after assembly, applying heat to the fastener and gap filler to remelt and reflow the conductive gap filler. Another method involves applying a conductive coating to the shank portion in lieu of applying conductive gap filler to sidewalls of the holes.