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Composite Tube bending properties

Composite Tube bending properties

Composite Tube bending properties

(OP)
I want to find the Young's Modulus of a composite tube (Concentric) made out of three tubes of different material glued together. Once the pipe is manufactured it will bend perpendicular to the axis. Can someone tell me where I can find the relevent equations.

Also I want to to find the poisson ratio for the composite tube. Is there an equation for this?

Thanks in advance.

RE: Composite Tube bending properties

Are you trying to estimate the bending stiffness of the composite tube around its neutral axis?

If so The trick is that M/I=s/y=E/R, or more usefully s/(yE)=1/R

R is the same for all three tubes, the strain (s/E) is the same for each at a given y.

Now you know that you can easily derive an expression for the total EI of the assembly.

 

Cheers

Greg Locock


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RE: Composite Tube bending properties


Are the three different materials fibre reinforced composite? Are the fibres directions different for the three tubes? In order to be of any help I think some more info would be necessary.

RE: Composite Tube bending properties

Differently from Greg, I understand that you have essentially a single tube, where three layers in the thickness are formed with different materials, right? A sketch would help much!
If I'm correct, and if I recall correctly the theory of reinf.concrete, you should do this:
-call E1 the elastic modulus of one of the three materials
-for the remaining two materials define n2=E2/E1 and n3=E3/E1
-now Ic=I1+n2I2+n3I3 and
σ1=My/Ic
σ2=n2My/Ic
σ3=n3My/Ic
Concerning the Poisson's ratio, I don't know how to combine them, and I suspect this would depend on the type of induced stress (if you are dealing with simple bending, what ere you doing with Poisson?). Anyway I would average the ratii on the area of the cross sections of the tubes.

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