SS Cables Strengthen Structure

The test should be a SS cable and a fiberglass woven 'cable' of the same thickness and hook it onto a tractor and a city council's lamp pole... see what gives first.

Or you could make the fiberglass 'cable' to the same weight the SS cable is and see if the council's pole is still up to it.

 

If one look at the leverage you have on the beam's length and the beam hight, would it be fair to say you have a 8000mm long / 400mm high x 2 halves ratio ?

If so, the cables would only add 1500kg of down force capability.

Only a few more layups or a simple added fiberglass structure inside the fiberglass beam should beat that.

One should keep in mind it is not only the beam bottom that stretches under load, but also the sides - at a height of 400mm there should be very very little movement

 

When looking at these types of things, I like to look at the actual mechanical properties of the materials. Density, Tensile strength(ultimate or yeild whichever is applicable) and young modulus(stretch). You will see that the units are pascals which is a force per area unit.

Material--------Density (g/cm3)--------Tensile Strength (MPa)------Young modulus (GPa)

E-Glass------------2.55---------------------2000--------------------80

S-Glass------------2.49---------------------4750--------------------89

Carbon-------------2.00---------------------2900--------------------525

Kevlar 29-----------1.44---------------------2860--------------------64

Kevlar 49-----------1.44---------------------3750--------------------136

316 Stainless Steel--8-----------------------650-800(annealed)-------187.5

These numbers are very rough and are only good enough for very basic calculations. Some of the numbers seem off to me but I only googled for a minute.

http://www.azom.com/Details.asp?ArticleID=764
http://www.alloywire.com/alloy_stainless_steel_316.html
http://www.azom.com/details.asp?ArticleID=863
http://en.wikipedia.org/wiki/Tensile_strength - Wikipedia explanation of ultimate and yeild tensile strength
http://en.wikipedia.org/wiki/Young's_modulus - Wikipedia explanation of youngs modulus
http://en.wikipedia.org/wiki/Yield_strength - wikipedia explanation of yeild strength

Try find the numbers for aluminium as well, it has good properties relative to the cost of the material.

The sides of your beam are doing relativley little work because the material is close to the neutral axis, but is essential for sheer loads.

 

Added material in the centre of the beam, say a meter to each side from the centre where the breakage would occur in case of an overload, should shift the load sideways and make for a much stronger and stiffer beam.

 

Hi Deepsix, sorry, I was referring to the down sides or vertical adges.