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Formula to Generate Mid-Plane

T

Tripp

Member
Hi Guys,

I am trying to create formula that will allow me to generate the mid plane of a particular layer in a laminate material, such that I can enter "n" no. of layers (max 20) with different layer thicknesses and have a formula that I can drag down and put inside an "if" function when I want a value displayed.

What I'm after is the mid plane of a particular ply plus (or minus) all the thicknesses of the plies in between, from the midpoint.

The formula normally for mid plane of ply "1" would be = (total thickness/2)-((tk)+(tk-1)+.....(ply2)+(ply1/2))

Below the total thickness for ply "n" would be =(total thickness/2)+((tk+1)+(tk+2).....+(n-1)+(n/2))

I have tried experimenting with count, sum and if to try and work from the midpoint but to no avail.

I have been looking at this work for a while so I may not have explained everything clearly enough. Questions welcome.

Regards,

Sam

Below is the diagram I've been using in my work.

upload_2014-11-3_17-29-8.png
 
This is probably easy to understand if you're in the business, but to a poor formula guy like me, I'm very confused. :eek:
Would it be possible for you to upload a spreadsheet showing some dummy example of what you want?
 
Hi Sam ,

I might be wrong , please correct me.

The geometric midpoint will always be half the thickness of the total laminate thickness.

If you want the distance from the geometric midpoint to the individual layer boundaries that is a more complicated calculation ; are you looking for this ?

Narayan
 
Hi Guys

Yes, I realise that it seems mighty complicated if you haven't been looking at it for as long as I have :(

I've attached a dummy version that should demonstrate what I'm after. Currently the formulas are not reactive as if I wanted more or less layers I would have to change the z values manually.

Narayan, I am using the geometric midpoint of the the total thickness to each layer, but not the layer boundary. I'm trying to get the distance from the geometric midpoint to the midpoint of each layer.

Initially I was using the count function to find the midpoint then trying to work from there. It might be I need another column with overall height, as Narayan has used, that has overall height included but I thought I would upload what I have so far.

Regards,

Tripp
 

Attachments

  • Laminate Calculator.xlsx
    34.1 KB · Views: 4
Hi ,

You have written :
I'm trying to get the distance from the geometric midpoint to the midpoint of each layer.
Click to expand...
but the diagram in your first post shows the distances from the geometric midpoint to the boundary of each layer.

Narayan
 
Hey,

Yes I used that diagram so that the first set of formula I gave made sense. At the end of each line I've put "Ply1/2" and "Plyn/2".

Sorry for the confusion.
 
The individual layer thickness is a manual input so it could vary. The only variable is the amount of layers and the subsequent z value. Angle and Thickness are input manually by design.
 
Hi ,

Can you see if this is OK ?

Please try to separate data from calculations.

Narayan
 

Attachments

  • Laminate_Layers.xlsx
    11.7 KB · Views: 16
Hey Narayan,

Thats perfect thank you.

I've been through the spreadsheet and I understand it, all except the [@[ when referring to layer midpoints (the last column). Could you explain how they are all referred to with just [@[?

Cheers,

Tripp
 
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