Mixing the materials
Do you think a composite propeller is made of solid fiberglass? Or carbon fiber? Kevlar? So did I at first. Most commonly a composite propeller is made of wood and covered with one of those materials. Composite just means a mixture of materials.
That's why homebuilders Ken Rand and Stuart Robinson get credit for having pioneered "composite construction" in the late 1960s when they glued Dynel cloth to carved polystyrene shapes to build their KR1 and KR2 airplanes. In 1969 Leo Windecker, D.D.S., helped Dow Chemical invent Fibaloy, a nonwoven glass fiber, allowing his Windecker Eagle to become the first FAA-certificated composite airplane. The reaction by general aviation pilots was, "Gee, you can't see it on radar." Then the military said, "Shut up. You can't see it on radar," and stealth technology was born. Now there are two new composite fighters on the way, and airline manufacturers are increasing their use of the materials. The first time you ride on a new Boeing 787, check the carbon-fiber-covered wings from inside your composite fuselage. (Light-sport-aircraft manufacturers like carbon fiber because it is lighter than fiberglass, and they face stringent weight restrictions.)
Use of carbon fiber in particular is growing by 10 to 15 percent a year — thanks mainly to airliner manufacturing and military uses, not to mention recreation. That means there is a shortage and very high prices; there won't be enough factories in the United States making carbon fiber for two years. Those general aviation companies using only fiberglass are the lucky ones, for now. Aside from the current shortage, any composite construction is labor intensive and therefore expensive. There also is a need to develop epoxy and resin materials that won't soften in high heat found on the ramp when the airplane is parked. The higher the temperature protection offered, the more costly the material. But despite the cost, the use of composites in aviation is here to stay. A scientist noted that they are half the weight of aluminum and 2.5 times lighter than titanium. But for companies still bending metal, switching is a huge start-up expense. There will continue to be all-metal airplanes until the supply of composite material goes up and manufacturing costs come down.— AKM
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