With its deft use of brushed aluminum for instrument bezels, pedals, handles and knobs, Audi AG's TT Coupe set a new standard in interior design when it made its debut at the Frankfurt Auto Show in 1995. The vehicle is credited with sounding a wakeup call, forcing automakers on both sides of the Atlantic to view interiors as ever more integral parts of the overall driving experience. Now, designers are experimenting with never-before used substances as well as new and unexpected applications of time-tested materials.

Since the TT's arrival, metallics have become increasingly popular and now are found in a wide range of vehicles, from luxury (Porsche Boxster) to entry-level (PT Cruiser). To complement this, designers are developing cloth and leather upholstery with metallic sheens. As more vehicles get aluminum or metallic interior accents, however, the danger of overexposure exists, and automakers looking for interiors that stand out must come up with innovative solutions.

To that end, Peter Davis, director of the Advanced Interiors Studio at General Motors Design, says the No. 1 automaker is focusing on an “honest” approach to plastics — in other words, plastics that don't have a false “animal” grain. Many suppliers appear to be on board with this newfound philosophy. As one Johnson Controls designer puts it, “Younger buyers want honesty. If it's synthetic, great, but don't make it fake.”

“We can do much more interesting things without trying to imitate nature with unnatural materials,” adds Rus Shafer, director of Industrial Design at Intier Automotive Interiors. Among them, Mr. Shafer says, are soft-touch paints on plastics to make harder parts feel softer and plastic parts that are translucent — a design influence borrowed from the trendy Apple iMac computer. Textron Automotive, at the behest of its OEM customers, also is experimenting heavily with soft-touch paints.

Luxury makers such as Mercedes-Benz and Jaguar continue to experiment with carbon fiber, especially on gearshift levers, center consoles and frame covers of sporty seats. “I can definitely see applications for it in a coupe or a sporty sedan such as the E-Class or AMG S-Class,” says Benjamin Dimson, chief designer and assistant general manager, Mercedes-Benz Advanced Design of North America.

Then, of course, there's the old faithful for interiors: leather. Historically seen as a status symbol, it's now becoming more practical for lower-end vehicles. A current trend toward leather-wrapped instrument panels, door inserts, consoles, gearshifts, steering wheels and dashboards threatens to transform leather into an everyday item. Some luxury marques are taking pains to keep their leather from becoming mundane.

“We are trying to push our suppliers to come up with a supple leather that gets as close to a furniture-grade aniline leather as possible in order to differentiate our leathers from everyone else's. We have to take it one step further by finding suppliers with more unique hides and a more unique texture,” says Mr. Dimson. Lorene Boettcher, international styling coordinator for Seton Co., says her company is working on producing leathers that are as soft as possible while still meeting OEM specifications.

The continuing popularity of traditional leather, which shows no sign of waning anytime soon, doesn't bode well for Ostrich Automotive Components, a South African consortium that is trying to sell automakers on putting more ostrich leather into cars and trucks. While a few manufacturers have experimented with the pimpled-looking material, many designers feel there just isn't a big enough demand for widespread use in production vehicles. Besides its high cost and low volumes, there are issues with the size, quality and quantity of ostrich hides compared to the much more ubiquitous cow hides. Some designers also suggest that ostrich leather is too aggressive-looking for most consumers to accept. “Once upon a time, it was probably a refined item, but today it's mostly seen as garish-looking,” one executive says.

Always on the lookout for something new and different, Larry Cole, executive product planning manager at DuPont Automotive, says his company is working on a material called Leather With Lycra (or LWL) for seating, shifters, and steering wheels. Designers are interested in it because it can be fitted around curved surfaces with less wrinkling and fewer seams than traditional leather alone, Mr. Cole says. DuPont continues to see interest from automakers for its Corian kitchen countertop product for use as accent trim on handles and knobs. Mr. Cole says the interest is coming from high-end marques — “the Jaguars and BMWs of the world.” He estimates the faux mineral plastic could be in luxury vehicles as early as three years from now. “We may even see it debuting at next year's car shows.”

Some suppliers and automakers also are looking at using recyclable materials such as cork and natural fibers. “With the right binder, cork is being considered as a viable alternative to wood as an accent trim,” says Thelma Sibley, manager of Sensory Element Design, Johnson Controls. GM's Mr. Davis says there are several international efforts under way to use natural scrap materials as fillers in seating as well as in areas that are actually seen by occupants.