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Sci Tech
Stronger materials for aircraft
Horse bone, aircraft
THE HORSE is no longer an unlikely source of inspiration for more efficient flight. So says a group of University of Florida engineers who are testing a plate that mimics an unique bone in the horse's leg with an eye toward lighter, stronger materials for planes and spacecraft.
The third metacarpus bone in the horse's leg supports much of the force conveyed as the animal moves. One side of the bone has a pea-sized hole.
Holes weaken structures, causing them to break than solid structures when pressure is applied. Yet while the third metacarpus does fracture, it doesn't break near the hole .
According to the University of Florida (UF) press release researchers are testing a plate that mimics the bone's uncanny strength in a form potentially useful for airplanes and spacecraft.
``Holes are a classic source of failure in engineered structures, but nature has found a way around that in this bone", said Andrew Rapoff, an assistant professor of aerospace and mechanical engineering.
Airplanes have holes for wiring, fuel and hydraulic lines. Engineers compensate for the weaknesses caused by these holes by increasing the thickness of the material around them.
But that approach adds weight, a problem for airplanes and spacecraft that need to be light, Rapoff said. The rule of thumb in the aerospace industry is that reducing the weight of a plane by one pound saves 10 pounds of fuel.
The engineers analysed the structure of the horse bone around its hole. They converted the resulting information into equations describing the bone's mechanical properties. They then developed a computer model that mimics the bone's behaviour under stress. They found that the bone was configured in such a way that it pushed the highest stresses away from the hole into a region of higher strength.
The engineers use this knowledge to create a "biomimetic plate," with a hole surrounded by several different grades of polyurethane foam to mimic the compositional structure of the bone near the hole. (Biomimetics describes the increasingly common engineering trend of mimicking natural solutions in manmade materials.)
The researchers tested the plate by placing it across two upright pillars and weighing it down, comparing the results with those from an identical test of a plate with a drilled hole without the foam stabilizer. It took twice the weight to break the biomimetic plate. Moreover, when it did finally break, the fracture did not go through the hole as occurred with the plate with the drilled hole.
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