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Working with exotic metals and composite materials

Children don't dream of being general aviation pilots with nice, sensible Cessnas. They want to fly screaming fighter jets that tear gaping holes in the sky and touch the edge of space. And when the military builds the most sophisticated attack plane out of exotic materials, adult children naturally attempt to produce their own fighter jet, at least one for the ground, by using those same materials in their cars. Is this just a silly dream, to put these high-tech parts in cars? Or is there a real advantage to using ultra-modern parts in your old restoration project?

First of all, let's be clear on our definition of an exotic material. For something to be exotic, it has to be rare or at least unusual in its class. We will concentrate here on exotic metals but also will make mention of some exotic nonmetals.

Exotic metals: Working with titanium
One of the first metals that may come to mind when you think of exotics is titanium. Titanium is not derived from iron, so it is considered nonferrous. The qualities of this material are really quite amazing. It is very resistant to corrosion, whether by chemicals or salt water. Even more impressive is that it has the highest strength-to-weight ratio of any known metal at normal room temperature. This means that a rod of titanium that is 12 inches long and weighs 1 pound will be stronger than any other piece of metal with the same dimensions. It is almost as lightweight as aluminum but can withstand much higher loads than most kinds of steel. 

So should everything be made of titanium? Well, it could, but not many of us would be able to afford it. The processes used to manufacture raw titanium are very time consuming and expensive. Reaching more than 3,000 degrees Fahrenheit is required to liquefy titanium, and at that point it likes to absorb hydrogen, oxygen and nitrogen gases. These gases are all very common in the air that we breathe, so titanium must be kept in an airtight environment when it is made. If this sounds a little complicated, then we can move on to the fact that after it is made, it is still quite difficult to machine when compared with steel or aluminum. 

Where titanium is used 
Where might you find titanium used? Besides the treads of Soviet tanks and the engines of fighter aircraft, there is a growing trend in the use of titanium in making the intake and exhaust valves of commercially available engines. Really though, working with titanium is most common in racing applications. 

Since the valves are much lighter in weight than stainless steel, the engines can run higher revolutions per minute (rpm) without danger of encountering valve float. (Valve float occurs when a valve moves so fast that its momentum causes it to continue opening even when it should be closing.) A reduction in weight helps to keep this from happening.

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.

Composite materials: Working with carbon fiber
As for exotic nonmetals 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 often are not worth the expense.

Its appearance in direct sunlight has to be one of the greatest benefits of using carbon fiber on a noncompetition 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 friends on a Saturday.

Stick with the tried and true
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 interested in car maintenance, 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.