Working with Metals: Exotics and Composites
By Matt Carlson /autoMedia.com
At Home with Titanium
So is there a future for titanium valves in your hot rod? Maybe. They are
probably available for your particular application, but for a price. As tough
as titanium may be, it still lacks the strength and durability of the old
standard steel valve. Titanium has a tendency to deform where it comes into
hard contact with other metals, and it galls, or sticks, when mating parts
must continually slide across it.
In a racing engine that is not expected to last more than a few races, these
drawbacks are entirely acceptable. In an engine that is designed to last a few
hundred thousand miles, they could begin to cause problems. A material like
titanium is best suited for racing applications where extreme light weight and
strength are priorities over cost and longevity.
Some other exotic metals that are used in aerospace are grouped in a category
called super alloys. Super alloys are designed for high strength under high
heat, such as what may be encountered in a jet or rocket engine. These
materials are rarely necessary in automotive applications that are not
involved in professional racing. They are typically heavy, and are designed to
offer maximum strength under very high temperatures.
As for exotic non-metals or composite materials, one of the most popular
aerospace composite materials to make it into consumer use is carbon fiber.
Carbon fiber fabric is infused with an epoxy that hardens much like fiberglass
– it is not carbon fiber alone that makes the material.
True aircraft carbon fiber composites are designed with high heat and strength
in mind. These materials are therefore usually made in special ovens to heat
and cure the epoxy chemicals. Most consumer-grade carbon fiber products are
made with an epoxy that cures or dries in the air. Once again, this kind of
material can be quite expensive, and the weight savings and strength are often
not worth the expense.
Its appearance in direct sunlight has to be one of the greatest benefits of
using carbon fiber on a non-competition vehicle. It's such a nice
three-dimensional, moves-when-you-look-at-it, shiny-but-not-shiny, mystery
material; just the thing to show off to the friends on a Saturday.
Should you buy into the high tech exotic material craze? Maybe. If you have
the money, and you like to have the most advanced things on the block, then
these materials are for you. However, if you are just a regular day-to-day
person, and you need the best value for your money, there are probably more
reasonable things to buy for your restoration projects. Sometimes the
tried-and-true methods are more reliable, and easier to service, than the
latest technologies. Leave the exotic materials for the next mission—the one
to the moon.