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General
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4. The Paradox of Composite Materials
When taken as a whole, a composite can withstand stresses that would break the weaker component,
whereas the composite’s stronger component can exhibit a greater percentage of its theoretical
strength than when loaded singly (G. Slayter).
Fiber Composites
The principle of combining different materials to form a composite with enhanced properties is just
as common in nature as in lightweight engineering.
This design method copied from nature has virtually revolutionized many fields of technology, with
the result that now for the first time extremely strong, but at the sa me time lightweight materials with
superior characteristics are available.
In particular the aerospace industries benefit from these low structural weights, which allow
considerable fuel savings and performance gains.
In space flight, high-performance fiber composites are used mainly for economic reasons. In view of
the high fuel costs, space agencies are prepared to spend up to 25,000 euros for every kilogram
saved. In aviation the figure is 250-750 euros per kg, in the automotive industry 0- 2.50 euros per kg
(with the exception of racing).
As fiber composites are usually more expensive than compact materials (e.g. metals) and place higher
demands on design and processing technologies, there is little incentive to use them in normal
automotive engineering, whereas their benefits for the aerospace industries are obvious.
With falling prices and growing, more generally available processing know-how composites are now
widely used. Motor sports, model construction and sports equipment design today could hardly be
imagined without them.
Applications in mechanical engineering are also gaining ground.
The Principle
A fiber composite (FC) is the result of combining several materials:
1.)
the matrix (e.g. epoxy or polyester resin), which gives shape to the final component, and
2.)
the reinforcing, highly tensile fibers (usually glass, aramid, or carbon)