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### Author Topic: Regarding EL allowables  (Read 3403 times)

#### orchidworld

• Posts: 42
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##### Regarding EL allowables
« on: September 05, 2012, 04:42:21 AM »
Hypersizer calculated EL allowables under the temporary laminates and selected faiture thoery, The Aij membrane stiffnesses of these temporary laminates are converted to effective laminate engineering elasticity values Ex, Ey, and Gxy.   these engineering contants are approximation? Because different ply sequencing is also affect the rusult of Allowables.
When the DL is generated, the allowables should be exact for this only DL.

i dont know whether my understand is right.

#### James

• Posts: 235
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##### Re: Regarding EL allowables
« Reply #1 on: September 05, 2012, 12:29:02 PM »
The engineering constants (Ex, Ey, and Gxy) are calculated from the Aij matrix for the EL. These terms are very accurate for ELs since they are based solely on the stiffnesses and thickness of the plies in the laminate. The laminate allowables are calculated based on the selected failure criteria. This is assuming a balanced/symmetric stacking sequence with evenly distributed stiffness.

See:
http://hypersizer.com/help/index.php#Materials/EffLam/el-properties-stiffness.php
http://hypersizer.com/help/index.php#Materials/EffLam/el-properties-allowables.php

The strength analysis for an EL should be very accurate for in-plane loads (Nx, Ny, Nxy). When bending moments are introduced, the EL analysis is less accurate than the DL analysis. Since ELs have a smeared bending stiffness, the laminate bending stiffness is based on homogeneous ply distributions. This will affect the calculation of strain due to bending loads as well as the buckling analysis.

See: