Some questions about PreComp

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Joined: Thu Nov 15, 2018 5:46 pm
Organization: Universidad Pública de Navarra
Location: Navarra

Some questions about PreComp

Postby Alvaro.Olcoz » Thu Apr 25, 2019 3:12 pm

Dear Jason,
I have encountered some doubts when using PreComp in order to find sectional properties of an own blade design for the first time. I will number them in order to make it easier for you to answer:

1) Regarding the ply concept, as I am not a native speaker, I dont know if I understand it well. Each lamina is composed by one or more plies, which are some kind of sub laminas? (i.e. a lamina formed by 5 plies, with a thickness of ply of 1 mm will make a lamina thickness of 5 mm ?). If this is correct, I do not understand why in the sample internal structure data input file (Figure 5) in PreComp user guide, the ply number assigned to the material "balsa" (Mat_id=5) is set to 0. Wouldn`t it mean that this lamina is not existing for the program? (as nº of plies * ply thickness = 0)

2.1) With respect to the material table in the sample file (Figure 9 in PreComp user guide ), in those materials that have the same Young's Modulus in both 1 and 2 directions (E1=E2), the classic equation of 2*G*(1+ν)=E does not need to be fullfilled? I found that it does not work for them.

2.2) Also regarding materials, do you have some information or reference about where the data (or commercil datasheet) was taken from? Which king of materials are the "gelcoat" and the "nexus"? As the nexus has the same moduli than the double-bias FRP with a bit lower density, I guess it is also a reinforced polimer.

3) Do you know if the sample file layout reproduces a real blade layout, or at least, if it is consistent with real blades' ? As I find it difficult to find information about material layouts, I have thought to calculate and average chord of the blade considered in the sample file, and scale the thickness of those FRP laminas taking into account my own blade average chord, which is a bit smaller. Do you think it will work for academic purpose, in order to calculate loads with FAST after the mechanical modelling of the blade?

Thank you very much in advance for your help.
Best regards,
Alvaro Olcoz Alonso
Public University of Navarre

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