Lightning Protection for Composite Fasteners via Conductive Layer
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Solution Overview
Problem
Current methods for lightning protection of carbon fiber reinforced plastic (CFRP) aerospace structures are complex and costly, leading to high manufacturing and maintenance expenses, particularly for fastened joints which are susceptible to direct lightning strikes.
Innovation Solution
A multilayer composite structure with integrated fastener-to-conductive layer surface lightning protection interconnections, featuring a co-cured conductive layer with chamfered recesses and carbon-fiber reinforced plastic (CFRP) layers, which increases the electrically conductive surface area for direct contact with metallic fasteners, allowing for effective dissipation of lightning currents through clearance fit fasteners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lightning protection methods are used for fastened joints in CFRP structures, then lightning protection performance is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The conductive layer is integrated directly into the composite structure during the curing process, merging the lightning protection function with the structural skin. This eliminates separate protection layers and reduces overall system complexity while maintaining protection effectiveness.
Solution Approach 2:
The conductive layer serves multiple functions: it provides lightning protection, maintains structural integrity, and facilitates current dissipation through fasteners. This multi-functionality reduces the need for additional dedicated protection components.
2Reliability
If conventional lightning protection methods are used for fastened joints, then lightning protection performance is improved, but manufacturing cost increases
Solution Approach 1:
The conductive layer is combined with the composite structure in a single manufacturing process, eliminating the need for separate assembly steps and reducing overall manufacturing cost while maintaining protection performance.
Solution Approach 2:
The conductive layer is pre-integrated into the composite structure during curing, preparing the lightning protection path in advance. This preliminary action eliminates the need for post-assembly modifications and reduces manufacturing complexity.
3Ease of operation
If standard fasteners are used in CFRP structures, then assembly is simplified, but lightning current dissipation is insufficient
Solution Approach 1:
The conductive layer acts as an intermediary between the fastener and the composite structure, providing a dedicated path for lightning current dissipation. This allows standard fasteners to be used while ensuring adequate current carrying capacity through the integrated conductive pathway.
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 reduces the complexity and cost of lightning protection for CFRP structures by enhancing current carrying capacity and facilitating the use of clearance fit fasteners, thereby lowering production costs and simplifying assembly, while maintaining effective lightning protection.
Implementation Method 1
The chamfered recesses in the co-cured conductive layer increase an electrically conductive surface area that contacts conductive, metallic countersunk fasteners installed within the plurality of holes
Data Source
Figure 1~2
Figure 3A~3D
Figure 3E
AI summary
A multilayer composite structure (52) with integrated fastener- to-conductive layer surface lightning protection interconnection employs a conductive layer (72) with an inner surface (61) and a plurality of chamfered recesses (68) forming countersinks (74) in an outer surface (59). A carbon-fiber reinforced plastic (CFRP) composite layer is disposed on the inner surface (61) of the conductive layer (72) and conforms to the surface shape. A plurality of holes (70) extend through the plurality of chamfered recesses (68) in the conductive layer (72) and the adjoining CFRP composite layer in a manner such that the conductive layer (72) defines a countersink portion extending into the openings of the plurality of holes (70). The chamfered recesses (68) in the conductive layer (72) provides an electrically conductive surface area that contacts conductive countersunk fasteners installed within the plurality of holes (70) to enable current sharing between groups of neighboring fasteners (78).