Apple Explores Metal-Ceramic Composites

Apple isinvestigating use of metal-ceramic composites to reinforce thin lightweightstructural housings for personal electronic devices.

"Themetal-ceramic composite component may be made of a metal-ceramic compositematerial containing at least one of aluminum, magnesium, titanium, zirconia andalumina," the company stated in a patentthat was approved March 22.

The compositerepresents another step in Apple's increasing sophistication in materials'technology.

Aspreviously reported by Design News,Apple is now a significant investor in a novel, but commercially unproven, bulkmetallic glass technologydeveloped at the California Institute of Technology.

Also in thegame as a housing material is carbon fiber reinforced plastics (CFRP), similarto the type of composite used in the Boeing Dreamliner 787.

Applerecently hired Kevin Keeney as a senior composites engineer. He had been CEO atKestrel Bicycles, an advanced user of carbon composite technology for frames.One of his accomplishments was developing a custom manufacturing process forvolume production of advanced composite products.

Apple'sexploration of the high end of the materials' portfolio is due to frustrationswith more traditional materials as devices shrink in size and demands rise forstrength and aesthetics.

Appledeclined to comment for this article, but spelled out the pros and cons ofvarious materials in the metal-ceramic composite patent.

Engineeringplastics, such as polycarbonate, nylon and ABS have these advantages: lowercost, lighter weight and the potential for colors, patterns and other visualeffects when compared with metal. "However, a plastic component may need arelatively large dimension (e.g., thickness) to provide sufficient strength,"states the patent. "Further, a plastic component may not be able tosatisfactorily resist scratch."

Metals mayprovide higher strength and scratch resistance than plastics, but may incurhigher material and manufacturing costs. Metals may also significantly addweight to electronic devices.

And the problemwith light metals such as aluminum or titanium is they may be costly or requirea large dimension to provide sufficient dent resistance and strength.

The proposedmetal-ceramic composite provides optimal strength, as well as light weight andthe opportunity to be shaped and anodized.

In thepatent, Apple describes several types of metal-ceramic composites. The mostconventional would be an injection molded shape. Lower density and high stiffness have longbeen practiced with Al-SiC (aluminum silicon carbide), says RandGerman, an expert in powder composites who was asked by Design News to review the patent.

Anotheroption for Apple is a ceramic matrix composite reinforced with discontinuousmetal fibers or layered coatings or multilayers.

Theinventors of the new metal-ceramic composite component are John DiFonzo, aproduct design manager at Apple, and Chris Ligtenberg, director of product designarchitecture at Apple.