When creating a laminate and then selecting the analyse button you can see the effective elastic engineering constants and the laminate failure allowables (both stress and strain Fu1, Fu2, Fsu12, eu1, eu2 & esu12). These are LAMINATE properties. You are using CLT for the elastic constants and the generated moduli are considered an accurate estimation. However, how are the strengths (Fu1, Fu2 & Fsu12) predicted?
When I then use this laminate in a composite PLY BASED analysis it uses the LAMINATE failure allowables for each of the analyses. Is this correct? I would have expected the orthotropic ply material stress and strain allowables to be used for a PLY based analysis. With the LAMINATE properties used in the LAMINATE based analysis.
However, when the laminate based analysis are selected in the failure tab it does not read across the pristine laminate properties from the created laminate. Why does it not read across the effective laminate failure allowables (Fu1, Fu2, Fsu12, eu1, eu2 & esu12)?
The following are values that are typical of carbon epoxy UD tape and are follows:
Orthotropic Et1 = 128 GPa, Et2 = 8 GPa, Ec1 = 120 GPa, Ec2 = 9 GPa, G12 = 3 GPa, Ftu1 = 2300 MPa, Ftu2 = 20 MPa, Fcu1 = 1200 MPa, Fcu2 = 150 MPa, Fsu12 = 90 MPa, etu = 0.018000, ecu = 0.011000
Hypersizer generated QI layup allowables E1 = E2 = 48 GPa, G12 = 18 GPa, Ftu1 = Ftu2 = 126 MPa, Fcu1 = Fcu2 = 362 MPa, Fsu12 = 89 GPa, eu1 = eu2 = 0.002633, esu12 = 0.004943
(It should be noted we consider the generated strength & strain values to be extremely low. We would expect tensile values higher than this and the tensile strength to be higher than compression strength. This material with this layup has been tested with Ftu1 = Ftu2 =600 MPa and Fcu1 = Fcu2 = 300 MPa. This would give strain allowables etu1 = etu2 = 0.012500 & ecu1 = ecu2 = 0.006250. Hence the question above about how are the strength allowables generated. We have also used the same material to create a Hypersizer laminate with 30% ±45° plies, 65% 0° plies, 10% 90° plies and the 90° direction has considerably higher strength and strain allowables than the 0° even though there is only 10% plies in the 90° direction!)
The ply based analysis uses the QI layup generated strain allowables of 2633 microstrain which is not the strain allowable of an individual orthotropic ply?
Your reasoning and logic for using the laminate allowable for a ply based analyses would be appreciated, as currently we are ignoring the ply based analyses except for OHT/OHC where we can input the damage tolerance strain allowables.