Charles Kim, Jae Kim
Composite materials have been adopted to replace metal in many industries and for a wide range of applications due to the materials strong mechanical and weight savings properties. One prime example is in the modern aerospace industry. Although the advantages of being light and strong have justified the adoption of composite materials, there is an issue - composite materials are not as electrically conductive as metallic structures. This is a problem because air vehicles require electrical performance to meet multiple electromagnetic effect (EME) requirements, such as EMI shielding, HERF protection, ground planes, survivability, signature management, and lightning strike protection.
To address electrical requirements and protect composite aircraft from electromagnetic effects, designers typically apply heavy, parasitic metals, such as expanded copper and aluminum foils, to the surface of the airframe. This is a problem because metals are heavy, integration is challenging, automation is limited, and the materials are often single-purposed (e.g. lightning strike purpose only), which require numerous materials to meet multiple requirements.
For this reason, we have developed VeeloVEIL, a lightweight, electrically conductive and electrically uniform material that provides 50-75% weight savings vs. expanded copper foils and multifunctional performance. For example, VeeloVEIL addresses both EMI and lightning strike in one material, while providing significant weight savings.
Over the past 18 months, we have developed a continuous roll production process of 36-inch wide metallized carbon fiber veil for this purpose. By controlling the amount of metal applied to the surface of the substrate, we can control the conductivity of the veil between the wide range of 1 mΩ/□ to 40 mΩ/□ and with a good uniformity of less than 5% COV. The carbon fibers in the base substrate give flexibility to the metallized veil, and low amount of metal coating can create a highly conductive path due to the network of non-woven carbon fibers. These factors allow our metallized veil to remain lightweight and very durable.
Just as a continuous roll provides an uninterrupted conductive path through its entire length, an increase in the width of the veil is also required for seamless composite structures. We are currently scaling our process to increase the width of the metallized carbon fiber veil from 36 inches to 60 inches. This scaling-up process is not simple, but, we have learned a lot from our maturation from 12 to 36 inches wide, a feat we accomplished without compromising quality.
Another challenge we are facing is the necessity of high throughput for large volume production. We have a technical approach and are able to leverage techniques from the highly mature web-handling industry. Web-handling and nonwovens is a $50B industry with existing scaled systems and robust supply chains. Our strategy is to leverage industry expertise to reduce risk and accelerate our timelines to meet demand for our technology.
Additionally, metallized polymer materials have been intensively investigated for applications unachievable by metals because of drapability, light weight, low cost, and the relative ease of creating complex-shaped substrates through molding. These efforts were enabled by the commercial metal-coating processes on ABS plastics, created by solving the poor adhesion problems of the coated metals, where the surface of a polymer substrate is chemically or physically modified to improve adhesion of the coated metal films. These treatments increase the chemical bonding at the interface and creates a rough surface suitable for coating metals.
However, the adhesion issues remain unsolved on most of the polymer materials. The nylon polymers have been known to be one of the hardest polymers to metallize. Currently, VeeloTech has characterized and solved the adhesion problem at the interface of metal and nylon fabrics, resulting in a strong adhesion of metals on nylon. VeeloTech will continue to develop the metal coating processes on other synthetic and natural polymers, where the light metallized polymers are suitable for the electromagnetic shielding in forms of wallpapers, tents, and jackets because of their good drapability. Finally, these metallized polymer materials will also be scaled-up to be produced at 60-inch width.
Charles Kim