In the quest for lighter and larger phones, Apple moved (back) to aluminium for its new iPhone 5. The result is a sleek, featherweight design with one problem: It’s easy to scratch. Whether or not the criticism is fair, complaints are taking on a life of their own among iPhone 5 owners, and the affair has been dubbed “Scuffgate” by the press. Better anodisation may be a solution, but Apple has quietly been working on another option – carbon fibre – for several years now.
As early as 2009, Apple’s carbon fibre guru, Kevin Kenney, filed for a patent on a reinforced phone case that could be a plastic composite stiffened with a carbon-fibre-reinforced plastic (CFRP) spine. Cyclists may already know Kenney as the former CEO of pioneering carbon-fibre bicycle maker Kestrel.
Carbon fibres’ light weight and unusual strength make them a natural stiffener for fast bike frames, as well as camera tripods, race cars, and airplanes. The carbon fibres themselves are three times lighter and four times stronger than steel.
Cost is often cited as a reason carbon fibre hasn’t found its way into more consumer devices. That’s too simple an explanation, however, especially considering the cost of phones these days – the 64GB iPhone 5 notches up a £700 price tag, for example – so there’s room to spend a bit more on the chassis. That said, carbon fibre presents several challenges in a phone, tablet, or laptop design. First among them is its low melting point, which makes CFRP difficult to machine or drill without deforming.
As a result, CFRP is best suited for single pieces that can be moulded with minimal connection points, like the glued together pieces of a carbon-fibre bicycle frame. The back side of a phone is certainly a candidate. In fact, there are already iPhone protective cases that use a flat sheet of CFRP to help protect the phone from drops and scratches.
Unfortunately, the issues with CFRP don’t stop with getting it into shape. It has very low thermal conductivity, making it ideal for items like camera tripods that need to be handled in cold weather. Phones and computer cases, though, need to bleed off heat generated by their electronics. CFRP chassis, like plastic ones, need a separate heatsink, precluding designs like the new Macbook, which relies on its aluminium unibody for cooling.
Coincidentally carbon fibre, like plastic, is not an EMI shield, so to avoid bleeding electronic noise into the world any CFRP phone could use its metal EMI shield as a heatsink. The only problem is that the addition of the metal shield adds back some of the weight that using carbon fibre is designed to reduce.
CFRP is also almost the opposite of aluminium or steel in many ways. It is remarkably stiff, which is great for protecting what’s inside from denting or bending, but once it reaches its limits it breaks rather than yielding. That means a CFRP chassis would need to be over-spec’d compared to a similar metal version.
Did Android already beat Apple to the punch?
For those keeping score in the interminable war between Apple and Android, they’ll be happy to know that there is already an Android phone with a partial carbon fibre chassis. Tag Heuer introduced the very cool looking, and very expensive Racer phone this summer. Priced at over £2,000, it isn’t flying off the shelves, but I’m sure they’re more than covering the cost of working with the material.
If you’re an Android fan tired of seeing iPhone 5 ads, check out this high-tech, if content-free, video promoting the Tag Heuer carbon-fibre-infused Android phone: