Software Use > Creating & Editing Composite Laminates

Effective Laminate Elastic Engineering Constants

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zoltan117:
When I create an effective laminate for a quasi-iso tropic layup (-45,0,45,90) for tape I dont get the same values for the engineering constants E1 and E2 ie E1 does not equal E2.

Is there a theory manual that shows what assumptions Hypersizer is making when developing the smeared laminate properties?

When I use our internal in-house code E1= E2.

Phil:
Please see the following link:

http://hypersizer.com/help/Content/Materials/EffLam/el-properties-stiffness.php


The engineering constants come from the inverse of the ABD matrix.  If the B terms are non-zero, it will throw off

Try making the laminate symmetric...  Instead of [-45/0/45/90], make it [-45/0/45/90]s instead.

zoltan117:
Does hypersizer calculate the correct effective laminate properties for unsymmetric layups?

mraedel:
I have problems to reproduce the elastic engineering constants in HyperSizer for single ply laminates with angles other than 0° and 90°.

I created a generic ply material and created effective laminates with (100% 0°, 0% 45°, 0% 90°); (0% 0°, 0% 45°, 100% 90°); (0% 0°, 100% 45°, 0% 90°). In the attached Excel spreadsheet I calculated the ABD-Matrix and from these values the elastic engineering constants according to http://hypersizer.com/help/#Materials/EffLam/el-properties-stiffness.php.

I checked the calculation with 2 composite analysis tools: eLamX² and alfalam. The calculations in my spreadsheet and the two composite analysis programs are identical.

However, for the (0% 0°, 100% 45°, 0% 90°) effective laminate, the engineering constants are different in HyperSizer than in all other calculations. They don't even match the values from the equations from the link.

What am I missing?

A second question: Why do effective laminates, defined as symmetric and balanced, create coupling stiffness terms in the B-matrix?

August:
The reason for the discrepancy is rooted in the way that HS handles 45deg plies when deriving the effective laminate properties. Because HS doesn't distinguish between percent +45 and -45 in the effective laminate definition, it assumes that the laminate is balanced.

So in your case, HS is assuming that the effective laminate is 50% +45deg tape and 50% -45deg tape. The result is that the A13 and A23 terms are zero for the effective laminate. When the A matrix for the effective laminate (pic attached) is inverted to calculate E1 and E2, you get different results than a discrete laminate that is 100% +45deg.

It is good practice to not use effective laminates as small as one ply, because the smeared property assumptions begin to break down. If you are having this problem in a design application, I would recommend switching to discrete laminates for your 1-ply case.

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