So I've been doing a lot of FEA simulations of 'skis' (wood core with fiberglass) lately, and a professor I was going over these with was convinced that the fiberglass properties I was using for these FEA simulation were incorrect. I used the properties listed directly from the manufactorer, so I really don't know how they could be wrong, but I figured I'd check here and get another opinion.
22 oz triaxial braided fiberglass from vectorply (where I got the properties from):
http://www.vectorply.com/pdf/e-tlx%202200.pdf
They give:
Ex = 3.88 MSI
Ey = 1.9 MSI
I was using:
Ex = 3.88x10^6 lbm/(in sec^2)
Ey = 1.9x10^6 lbm/(in sec^2)
What is wrong here?
Fiberglass properties
Moderators: Head Monkey, kelvin, bigKam, skidesmond, chrismp
The lbm is really throwing me off. Thankfully, most of my textbooks emphasize the metric system more and more (international manufacturing and collaboration) and all the ones that I currently have avoid using pound-mass.
I haven't taken FEA yet, so maybe I am missing something, but those units look wrong. What I do remember is from a few years back when I was working with some material properties/testing. The MSI was just mega pound/in^2. KSI=kilo pounds/in^2 and of course, PSI=pounds/in^2.
lbm/(in sec^2) seems like some sort of a moment. A quick Google search turns up a few things that are "flow resistance coefficients". I can ask a few people tomorrow and see what they think.
I am kind of surprised that your prfo can;t figure this out though.
I haven't taken FEA yet, so maybe I am missing something, but those units look wrong. What I do remember is from a few years back when I was working with some material properties/testing. The MSI was just mega pound/in^2. KSI=kilo pounds/in^2 and of course, PSI=pounds/in^2.
lbm/(in sec^2) seems like some sort of a moment. A quick Google search turns up a few things that are "flow resistance coefficients". I can ask a few people tomorrow and see what they think.
I am kind of surprised that your prfo can;t figure this out though.
He's difficult to work with and just criticizes the work instead of trying to find out what is wrong...
I'm with you on the units though, it just doesn't make any sense to me. I did not take FEA either, but the other person I'm working with did and says that they always used PSI for the lbm/(in sec^2).
Going more into this though, the modulus that we have for the fiberglass IS lower than those we have for our woods, and the prof. doesn't see how that is possible, or why we'd even use a fiberglass if that was the case. I'm not an expert at all on this and just assume what he's saying is right, but does anyone else have any input on this?
I'm with you on the units though, it just doesn't make any sense to me. I did not take FEA either, but the other person I'm working with did and says that they always used PSI for the lbm/(in sec^2).
Going more into this though, the modulus that we have for the fiberglass IS lower than those we have for our woods, and the prof. doesn't see how that is possible, or why we'd even use a fiberglass if that was the case. I'm not an expert at all on this and just assume what he's saying is right, but does anyone else have any input on this?
-Pat
melvs wrote:Going more into this though, the modulus that we have for the fiberglass IS lower than those we have for our woods, and the prof. doesn't see how that is possible, or why we'd even use a fiberglass if that was the case. I'm not an expert at all on this and just assume what he's saying is right, but does anyone else have any input on this?
Wait...
What wood are you using? 3.88 MSI=3,880,000 PSI!