

Leaked image of the Galaxy S IV  (Source: evleaks)
Plastic likely to be used extensively in the Galaxy S IV




Source: CNET

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By Solandri on 3/6/2013 4:02:02 PM , Rating: 3
I've seen iPad's dropped so many times the corners are caved in and it still operates as new.

This is why metal is bad for mitigating falling damage. It has a rather stiff young's modulus (it doesn't deform much for a given stress). That means the deceleration forces from a fall are high, resulting in the metal quickly entering the permanent deformation region. And you end up with caved in corners.

With a more flexible material like plastic, the energy of the fall is dissipated over a greater distance/time, reducing deceleration forces, and thus reducing the likelihood of permanent damage. The plastic corner bends a lot more, possibly even resulting in the different major pieces of the phone snapping apart. But because the bending spreads out the forces and reduces the peak stresses, there's less chance of permanent deformation being done (other than a few scuff marks) and after the impact everything just snaps right back. Fighting styles like judo embrace this philosophy - minimize damage by redirecting the energy of blows instead of trying to resist them entirely.

HP (the old HP) understood this when designing their original Laserjet printers, the ones that weighed 50-75 lbs. People complained about the exterior being "cheap plastic". But the things could fall off a table, bounce around, and they'd continue to work perfectly fine. If it had been metal it would've deformed, the interior pieces would no longer be aligned, and it wouldn't function as a printer anymore. For the damage modes most frequently experienced by laser printers, "cheap plastic" was the superior exterior material choice. Heck, Apple understood the same thing when they made their laptop power plugs magnetic, instead of a long, rigid physical plug and socket.

No I'm not saying metal sucks. Materials all have a different roles based on their dozens of different properties, and it's the engineer's job to pick the material whose properties best suit the needs of the task at hand. If people were using their phones to support large weights or to hold things solidly in place or to provide puncture resistance, then yes I'd agree metal is the better choice than plastic. But for a device whose primary damage risk is falls from about 3-5 feet, you want a softer, flexible material on the exterior to take the brunt of the impact forces while the interior is protected by a stronger frame/chassis.

If the phone doesn't have that soft, flexible exterior, people feel compelled to buy one to protect the phone. That's why most iPad/iPhone owners buy a protective case. The metal is mostly decorative, not functional, so they feel it needs additional protection. I never really understood this - it's like buying a plastic wrap for your sofa to protect it from spills. If spills on the sofa are a concern, it should be designed from the beginning to be spill-resistant. And that's what the plastic back cover does. In essence the plastic back is your protective cover. And it's cheap and easily replaced if it gets too scuffed up for your tastes (a quick Google search says you can get them for the S3 for less than $10, probably less than $1 wholesale, making it cheaper than most protective cases).


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