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Selection
Issues
In
a quest for light-strong structures, the density of a selected
material will be another important parameter. In general, the lower the
material density, r, the more of it that can be used to perform a
certain task if the system mass is fixed.
The quantities (E/r), (E/r2), and (E/r3) are all employed in material selection for different
tasks. The diagram shows a log-log plot of Young's modulus versus density for
a wide range of materials. The yellow zone is metal alloys, the blue polymers,
the green composite materials, and the brown woods. The red line represents
a selected value of (E/r). All materials above the
line have a higher value of this parameter, all below the line a lower value.
If the selected value of (E/r) is related to a design
criterion, those materials above the line exceed this criterion and merit further
examination. |
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