Laminate, metal+reinforced resin

Johan_S

Hi Forum
I have never done laminates before and I will appreciate any help.
I have to analyse a pipe with a thin spot on the inside and the intention is to reinforce it with a fiber/resin on the outside. The pipe is subjected to pressure, a bending moment and an axial load.

I attach a file with a simplified model of what I think I should do.
My questions are:

* Can a 2-layer laminate work?
* Does it matter in which order the properties are entered in the laminate input window?
* Which layer is top and bottom?
* Internal or CCX solver?
* Anything else I should be careful of?


Thank you in advance.

disla

* Can a 2-layer laminate work?

There will be peak stresses close to the Laminates discontinuities. With solid elements those discontinuities between the healthy pipe and the corroded area can be smooth.
If you have bending maybe, you want to look at the through thickness shear. It will be better captured with solids.

* Does it matter in which order the properties are entered in the laminate input window?

Absolutely Yes. Each index refers to one local Axis. 1=U, 2=V, 3=W
You must define an Orientation BC (preferably the same for all the elements) and an additional GLOBAL=NO custom CARD to properly read the results.
That’s the only way to warranty a full control of your laminates position and fibers orientation. 1st line in layers material properties is the one with smallest W local coordinate value.

* Which layer is top and bottom?

The question is ambiguous. W local axis direction determine the layers order.
If you have any doubt, prepare a 2-layer laminate 1st-20mm and 2nd-1mm. CCX expands the laminates, and you will be able to check it on the results window.

* Internal or CCX solver?

CCx and Internal solver manage Laminates different. Mecway solves Laminates by transforming the composite layers into the equivalent orthotropic material by means of the ABD Matrix.
Ccx expands the composite shell element into a unique 3-D Brick element to solve and then, the stresses are computed using each layer property. This is possible because there are more integration points, and they are assigned the material properties appropriate for the layer they belong to.
I have tested Laminates with both internal and Ccx and from my point of view CCX performs better.
Quadratic elements and reduced integration seem the safest combination.

* Anything else I should be careful of?

There is some mess on your layer’s properties. I guess you want all the reinforcement the same.
I would offset the shells to align them on the outside.
¿Will you “close” the pipe?. Hoop Stress is sustained by the Resin thickness in tension. The Longitudinal Stress (aprox ½ the hoop Stress), is sustained only by the Resin adherence to the pipe surface.

Johan_S

Disla
Thank you for this really comprehensive reply. I really appreciate it.
Yes my real model will be properly loaded, I have only applied radial pressure to keep it simple.