I am planning to make A arms and the push-rods using carbon fibre tubes.

get hold of a book and design them, do not use off the shelf pultruded tubes as they are not designed for this purpose

You will need to calculate the right tube specification.

The basic data for our range of roll wrapped tubes is:

                                                                                                                                                                                                                                                                                                

Property	This Carbon Fibre Tube	Steel	Aluminium
Density (g/cc)	1.60	8.0	2.7
Youngs Modulus 0°(GPa)	90	207	72
Youngs Modulus 90°(GPa)	19	207	72
In-Plane Shear Modulus(GPa)	4.6	-	-
Major Poisson's Ratio(MPa)	0.14	-	-
Ult. tensile Strength 0°(MPa)	750	990	460
Ult. comp. Strength 0°(MPa)	600	990	460
Ult. tensile Strength 90°(MPa)	400	990	460
Ult. comp. Strength 90°(MPa)	350	990	460

You will then need to use those figures and compare the calculations with the tube sizes we offer to see if the sizes are suitable for your needs.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

how to calculate the tube specifications from the given load
i am unable to find an approach
could you please guide ??

You need to calculate look at the arrangement you are going to use, calculate the forces (which you have calculated axial by the looks of it) but is there any bending or shear induced due to the mounting type?

Then design separately for:
Pure Axial tension
Pure Axial compression
Axial tension / compression with nominal bending from the axial force and a nominal lever arm
Bending moment capacity
Buckling moment capacity
Combined buckling and axial forces (tension and compression)

Then:
Check deflection in all load cases for calculated stiffness of tube and arrangement.

The tube will most likely be a combination of UD at 0, +/-45 and 90deg to the C/L

You need to derive it mathmatically.  The figures given above are all relative to the surface area the force is being exerted through - look at the definition of the units......

If you arent using FEA as part of CAD software then you have a lot of equations to derive mathematically all mostly based on Newtons laws, Euhlers equations of motion, hooks law etc etc etc. the more you simplify the model the less complicated the maths is.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant