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Join Date: Nov 2007
Location: Bangalore, India; 12.981550 N 77.531867 E
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### Re: Optimized Engineering Materials Through Cleantech

07/15/2011 9:48 PM

Derived Properties that Help in Materials Selection

The initial selection of appropriate engineering materials for particular type of application is not based on mere Tensile Strength and Elastic Modulus. If that were so, very few engineering materials would compete with Steel. The following Derived Engineering Properties may be noted:

1. Specific Tensile Strength: This is mathematically derived as:

Tensile Strength/ Sp wt (Unit = Meter)

In conceptual terms this could be viewed as the Length of any Material that hangs on a ceiling and the resultant weight creates sufficient stress at the "anchor" point to effect "Breaking Load" by its own weight. The cross section being unity

2. Equivalent Weight Section: This is mathematically derived as the Section depth of a rectangular beam having unit width in cross section, wherein the resultant cross section x unit length (volume) has the same weight of low Carbon Steel beam with unit width. Its unit is in cm

(Schematic ... Not to Scale)

3. Equivalent Weight Rigidity factor: This is mathematically the multiplication of Elastic Modulus of the material in question by the Moment of Inertia of the Rectangular beam cross section as in 2 above. Its unit would be in Kg-M2

Let us look at some Derived Engineering properties of a few Composite materials

 Fiber (40% uni-directional) Tensile Strength Sp.wt Sp. Tensile Strength Tensile Modulus Eq Wt Section Eq. Wt Rigidity Modulus Cost Factor (MPa) (kg/m 3) (m) (GPa) (cm) Carbon Steel = 1 cm (Kg-m 2) (Rs/ Kg) Bamboo 293 600 48833 18.32 13.08 3416 250 Hybrid Bamboo1 440 688 63953 22.85 11.4 2282 740 Hybrid Bamboo2 438.2 695 63050 27.09 11.29 3248 990 E-Glass 816.8 1474 55413 18.91 5.32 237.27 270 S-Glass 1104 1455 75876 23.16 5.39 302.22 510 Carbon Fiber 1222 1336 91467 74.95 5.87 1263 3210 Kevlar 49 1298 1243 104424 45.27 6.31 947.8 2210 Boron 946.5 1467 64519 92.94 5.35 1186 3810 High tensile Steel 4000 7900 50632 210 0.99 16.98 250 Low Carbon steel 400 7850 5095 210 1 17.5 60

[NOTE: 1. Hybrid Bamboo1 comprises Bamboo 30% Kevlar49 10%; Hybrid Bamboo2 comprises Bamboo 30% Carbon Fiber 10%; The different properties are based on estimations using available data, and are only for comparative study.]

It would be noted that Composites based on Bamboo could be strong contenders to compete with even specialty (exotic) Engineering Composites consisting of "KEVLAR-49" and Carbon Fiber

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