Composite Prepreg Lightning Strike Resistance via Fibre Migration
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Solution Overview
Problem
Composite materials used in aerospace structures are vulnerable to lightning strikes due to low electrical conductivity in the z-direction, leading to potential catastrophic damage, and existing solutions to enhance conductivity often increase weight and compromise mechanical properties.
Innovation Solution
The process involves manipulating structural fibres to create conductive free filaments before resin impregnation, which migrate into the resin layer during curing, forming an electrical pathway without adding conductive elements, thereby enhancing z-direction conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive elements are added to enhance z-direction electrical conductivity, then lightning strike resistance is improved, but weight increases
Solution Approach 1:
The structural fibres themselves serve the dual function of providing mechanical strength and generating electrical conductivity through self-organizing migration during curing, eliminating the need for separate conductive additives and maintaining lightweight properties
Solution Approach 2:
The electrical conductivity parameter is enhanced by changing the spatial distribution and concentration of conductive fibres through temperature-controlled migration during the curing process, rather than adding conductive materials
2Reliability
If conductive elements are added to enhance z-direction electrical conductivity, then lightning strike resistance is improved, but mechanical properties are compromised
Solution Approach 1:
The structural fibres perform both structural and conductive functions simultaneously, avoiding the need for separate conductive elements that would compromise mechanical integrity
Solution Approach 2:
The conductive network is formed in advance during the curing process through fibre migration, ensuring both mechanical strength development and electrical conductivity establishment without interfering with each other
3Reliability
If elaborate processing methods are used to add conductive particles, then lightning strike resistance is improved, but manufacturing complexity increases
Solution Approach 1:
The fibres automatically migrate and self-organize into conductive networks during the standard curing process, eliminating the need for elaborate processing equipment or complex manufacturing steps
Solution Approach 2:
The complex processing steps for adding and distributing conductive particles are removed entirely, replacing them with the simpler approach of allowing fibres to migrate naturally during curing
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 approach results in lightweight composite materials with excellent mechanical properties and significantly reduced electrical resistance in the z-direction, making them more resistant to lightning strikes without compromising mechanical performance.
Implementation Method 1
As the resin is heated its viscosity drops and the free fibres are free to migrate into the resin layer away from the interface
Implementation Method 2
As the temperature rises further, the resin begins to cure, fixing the free filaments in place distributed within the resin layer
Implementation Method 3
the free fibres are believed to form electrical contacts between themselves and bridging the resin layer, thus increasing the electrical conductivity in the z-direction
Data Source
Figure 1~2
Figure 3
Figure 4a~4d
AI summary
The invention relates to a prepreg comprising a structural layer of conductive fibres comprising thermosetting resin in the interstices, and a first outer layer of resin comprising thermosetting resin, and comprising a population of conductive free filaments located at the interface between the structural layer and the outer resin layer which, when cured under elevated temperature, produces a cured composite material comprising a cured structural layer of packed conductive fibres and a first outer layer of cured resin, the outer layer of cured resin, comprising a proportion of the population of conductive free filaments dispersed therein, and to a process for manufacturing prepregs wherein the electrically conductive fibres pass a fibre disrupting means to cause a proportion of the fibres on an external face of the sheet to become free filaments.