Conductive Surfacing Material for Composite Structures
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Solution Overview
Problem
Aerospace composite materials face challenges in protecting against lightning strikes and fluid ingress, requiring enhanced electrical conductivity without increasing aircraft weight, and existing solutions do not adequately address these issues.
Innovation Solution
An integrated conductive surfacing material comprising a thin conductive layer sandwiched between a stiffening thermoplastic layer and a curable resin layer, with a nonwoven layer on top, designed for automated placement processes like AFP, providing lightweight, flexible, and fluid-barrier properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive layer is added to protect against lightning strikes, then lightning strike protection is improved, but weight increases
Solution Approach 1:
The patent applies a thin film conductive layer (5-25 micrometers thick) made of conductive fabric or foil between the surfacing material and composite structure. This thin film provides lightning strike protection while minimizing weight increase compared to traditional thick conductive layers or mesh structures.
Solution Approach 2:
The patent creates a composite surfacing material system consisting of multiple layers: surfacing material, conductive layer, and adhesive layer. This composite structure integrates lightning protection functionality into the existing surfacing material without requiring separate heavy protective components.
2Reliability
If a thick conductive layer is used to ensure conductivity, then electrical conductivity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent combines the conductive layer with the surfacing material installation process. The conductive layer is positioned between the surfacing material and composite structure, allowing all layers to be bonded together in a single manufacturing step rather than requiring separate installation of conductive protection layers.
Solution Approach 2:
The conductive layer is pre-positioned and adhered to the composite structure before the surfacing material is applied. This preliminary action ensures proper conductivity configuration before final assembly, simplifying the overall manufacturing process.
3Stability of the object's composition
If a non-porous thermoplastic stiffening layer is used, then structural stability is improved, but fluid barrier performance worsens
Solution Approach 1:
The patent uses a thin film conductive layer (5-25 micrometers) that acts as a fluid barrier while maintaining structural stability. The thin film nature prevents fluid ingress through the conductive layer without requiring thick non-porous materials that would compromise flexibility or stability.
Solution Approach 2:
The patent applies different properties to different layers: the surfacing material provides structural stability and stiffness, while the thin film conductive layer provides localized fluid barrier and electrical conductivity functions. Each layer is optimized for its specific function rather than requiring all layers to be thick and non-porous.
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 solution effectively enhances lightning strike protection and prevents fluid ingress while maintaining a lightweight structure, suitable for aerospace applications, and is compatible with automated manufacturing processes.
Implementation Method 1
The composite materials used in the fabrication of aerospace component parts must have certain characteristics to protect the parts from damage or hazards caused by common environmental occurrences such as lightning strikes... enhance the electrical conductivity of the composite structure to provide lightning strike protection
Implementation Method 2
Fluid and moisture ingression into composite sandwich panels containing honeycomb or foam core is a common problem... The stiffening layer is a non-porous thermoplastic layer... providing lightweight, flexible, and fluid-barrier properties
Data Source
Figure 1
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AI summary
Multifunctional surfacing materials for use in composite structures are disclosed. According to one embodiment, the surfacing material includes (a) a stiffening layer, (b) a curable resin layer, (c) a conductive layer, and (d) a nonwoven layer, wherein the stiffening layer (a) and the nonwoven layer (d) are outermost layers, and the exposed surfaces of the outermost layers are substantially tack-free at room temperature (20°C to 25°C). The conductive layer may be interposed between the curable resin layer and the stiffening layer or embedded in the curable resin layer. According to another embodiment, the surfacing material includes a fluid barrier film between two curable resin layers. The surfacing materials may be in the form of a continuous or elongated tape that is suitable for automated placement.