Spreadsheet on composites properties 1

[vinhermes]

Dear All,

First of all thank you for all the information this forum has provided me. This is my first post as I have just been graduated in Naval Architecture; so I am not a composites expert but can expect to design parts at some point.

It is very hard to find free spreadsheets on the internet to calculate laminate properties as it seems that everyone keeps its own. So I am happy to give this one, which is just basic for the moment but will hopefull grow with time (cores, outer skins, stresses at each ply, etc.). But before I go further, I would be happy if some of you could double-check the results obtained as I do not have a feel for all these numbers yet. No doubt this will come with experience.

So here is how it works:

- Page one is used to define the materials properties. So that it is pretty easy to make the spreadsheet evolve with time. I you don't think that have changes to make for the moment
- Page two is the calcultor itself. Just play with the yellow cells and see the results appear.
- Page three is the formulae references: very basic rules of mixture for the moment.

Sorry for my spelling mistakes but I am french. Thanks by advance for all your constructive comments.

Best regards, Vincent

 

[rstupplebeen]

First, thank you for posting your work instead of just asking for others. You should be able to use this to validate your results.

http://math.materials-sciences.com/webMathematica/MSC/start.html

I hope this helps.

Rob Stupplebeen

 

[vinhermes]

Thank you Rstupplebeen.

Is this the way I should go to take into account all the differences in orientation, fibre weight fraction fibre, matrix, stacking sequence? Or do you think there is a more approriate way to do this?

If someone has an example, I would be really grateful as this is quite a lot of work and I would like to make sure that I am in the right direction.

Thanks to all. Vincent

 

[RPstress]

Using micromechanics to find the lamina properties like this is generally not used a great deal; usually the 1-, 2- and 12-direction (the 12-direction being shear) ply properties for the fibre and matrix together are measured. I think that the micromechanics equations are right, but using the carbon longitudinal fibre modulus as the fibre transverse modulus is probably wrong. Carbon fibre transverse properties are quite hard to establish and are not often documented, as carbon fibres themselves are a markedly anisotropic material (whereas glass fibres can usually be taken to be isotropic).

Also, with the woven roving you've taken the fibre/matrix property in the '0' direction to be the same as for UD, then also used this as the WR '90' modulus. If calculating the woven material's lamina properties from micromechanics you need to take account of the proportion of fibres in the 1- and 2-directions. Additionally, with woven material the fibre properties are not fully realised because of fibre crimp when in woven form. Roughly speaking, your micromechanics-calculated '0' and '90' moduluses should be halved, and an additional arbitrary knockdown of about 0.9 applied for crimp.

An option to enter the lamina properties without the micromechanics stage would help with this, as there is no easy way to calculate the crimp knockdown factor.

I haven't checked your calcs on ply directions yet.

(NB: you've tended to use '0°' to mean the direction of the fibres when calculating the lamina properties. It's more conventional to use the term '1-direction' for this, and reserve the terms '0°', etc., for the laminate.)

 

[RPstress]

Some transverse direct and shear fibre moduluses can be found at:

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA340559&Location=U2&doc=GetTRDoc.pdf

(DOT/FAA/AR-95/29 "Fiber Composite Analysis and Design: Composites Materials and Laminates, Volume 1".)