In 2007, Apple applied for and was granted a patent for a method of manufacturing carbon fiber that allows for consistency in the surface appearance. Because of the lack of uniformity common to carbon fiber, most finished products made of the material are essentially inconsistent in appearance. However, because of the strict requirements mandated and perfection sought by Apple as a brand, this lack of consistency has prevented the tech behemoth from utilizing carbon fiber in any of their products.
A quote from the patent argues against other methods of carbon fiber production in saying,
“As a result, the resulting carbon fiber composite can have cosmetic imperfections that reduce the aesthetic appearance of the molded article formed therefrom.”
To combat this issue, Apple filed patent US 7790637 B2, which details a method of creating consistent appeal without risk of aesthetic imperfections. The patent relies on a “scrim layer” which are the outer most layers of fabric (the visible layers), being used to combat this issue.
“A scrim layer provided on an exterior surface of the plurality of sheets of prepreg, wherein the scrim layer and the sheets of prepreg form a composite laminate and the scrim layer constitutes an outer, exposed surface of the composite laminate, wherein the scrim layer is made of a nonwoven mat of randomly oriented fibers and provides the outer surface of the composite laminate with a consistent appearance.”
This nonwoven mat, although it has a lesser degree of structure and uniformity that are found in CF threads and weaves, in its minuscule randomization achieves an appearance of uniformity unavailable to typical CF constructions. The distinction is akin to the differences between a tweed jacket and a merino sweater. Though both are made of wool, the sweater appears more uniform because of the lack of organized, patterned threads.
The nonwoven mat of fibers is becoming a bigger and bigger trend in carbon fiber manufacturing. For example, Lamborghini is using forged carbon fiber for more of its parts in their exotic vehicles.
So what exactly is “forged” carbon fiber and why is it being used? Forged composites use a patch of fibers (500,000 turbostratic fibers per square inch) mixed with resin that is then put under high compression to “stamp” out pieces in a matter of minutes or even seconds, in nearly any molded shape imaginable. This variation of carbon fiber allows for the creation of new shapes not possible from the traditional woven fabric due to the existing physical limitations. While this is revolutionary in respect to the variety of products now available for production, forged carbon fiber is not proven to provide the inherent strength woven or uni-directional composites currently offer.
What makes this patent unique?
What differs from forged carbon fiber as opposed to Apple’s patent is the actual look of this layer. According to Apple’s patent, they developed a method to make a scrim layer that is consistent in appearance every time. What this means is unclear to the public, but one assumption can be that they created a homogeneous paste that when applied to the mold, appears uniform in appearance.
Why would they not use it until now?
Carbon fiber is a conductive material, as well as RFID blocking. This has its benefits and drawbacks for electronics. Depending on the location within the phone, it can be beneficial as carbon fiber is 40x more heat conductive than aluminum. Thus, it could be used for its strength and as an insulator. However, even though CF is an extremely strong and lightweight material, it could reduce the signal strength if used as the outer shell of the phone incorrectly. This may be the largest challenge for Apple to overcome before it can use this revolutionary material in its phones.
Why could forged carbon fiber be important for the iPhone 8 in particular?
Early rumors have hinted at an edge to edge screen, even extending all the way down to the lightning port. This will reduce the amount of aluminum Apple can use on the edges, which would make the casing significantly weaker in terms of breaking point. In order for the company to continue making phones lighter and thinner, a new material, manufacturing process, or design will need to be used, hence forged carbon fiber. Is there a chance the patent will never be used for Apple’s phones? Yes. But as technology continues to evolve, it would not be surprising to find it in one of their product lines, perhaps sooner than later.