Apple is
investigating use of metal-ceramic composites to reinforce thin lightweight
structural housings for personal electronic devices.
"The
metal-ceramic composite component may be made of a metal-ceramic composite
material containing at least one of aluminum, magnesium, titanium, zirconia and
alumina," the company stated in a patent
that was approved March 22.
The composite
represents another step in Apple's increasing sophistication in materials'
technology.
As
previously reported by
Design News,
Apple is now a significant investor in a novel, but commercially unproven, bulk
metallic glass
technology
developed at the California Institute of Technology.
Also in the
game as a housing material is carbon fiber reinforced plastics (CFRP), similar
to the type of composite used in the Boeing Dreamliner 787.
Apple
recently hired Kevin Keeney as a senior composites engineer. He had been CEO at
Kestrel Bicycles, an advanced user of carbon composite technology for frames.
One of his accomplishments was developing a custom manufacturing process for
volume production of advanced composite products.
Apple's
exploration of the high end of the materials' portfolio is due to frustrations
with more traditional materials as devices shrink in size and demands rise for
strength and aesthetics.
Apple
declined to comment for this article, but spelled out the pros and cons of
various materials in the metal-ceramic composite patent.
Engineering
plastics, such as polycarbonate, nylon and ABS have these advantages: lower
cost, lighter weight and the potential for colors, patterns and other visual
effects when compared with metal. "However, a plastic component may need a
relatively large dimension (e.g., thickness) to provide sufficient strength,"
states the patent. "Further, a plastic component may not be able to
satisfactorily resist scratch."
Metals may
provide higher strength and scratch resistance than plastics, but may incur
higher material and manufacturing costs. Metals may also significantly add
weight to electronic devices.
And the problem
with light metals such as aluminum or titanium is they may be costly or require
a large dimension to provide sufficient dent resistance and strength.
The proposed
metal-ceramic composite provides optimal strength, as well as light weight and
the opportunity to be shaped and anodized.
In the
patent, Apple describes several types of metal-ceramic composites. The most
conventional would be an injection molded shape. Lower density and high stiffness have long
been practiced with Al-SiC (aluminum silicon carbide), says
Rand
German, an expert in powder composites who was asked by
Design News to review the patent.
Another
option for Apple is a ceramic matrix composite reinforced with discontinuous
metal fibers or layered coatings or multilayers.
The
inventors of the new metal-ceramic composite component are John DiFonzo, a
product design manager at Apple, and Chris Ligtenberg, director of product design
architecture at Apple.
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