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Thread: AFR for Monocoques

  1. #1

    AFR for Monocoques

    Reading over the SRCF, it says "You must also include all the test data specified in the rules and in the Structural Equivalency Spreadsheet. It is recommended you attach the SES with test data along with this SRC form. You may leave the tabs blank that are part of the equivalency process." Does this mean we have to do physical testing for all different lay-ups used? So far I have just been finding properties of the carbon and core separately and doing ply-based analysis in Hyperworks. That way we can get an optimized variable layup throughout the whole chassis. But if we have to do testing for every single one of these layups doesn't that defeat the purpose of doing AFR? Thanks for the help.

  2. #2
    Junior Member
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    Hey Diebel, I came to the same conclusion. I ended up using zone based optimization rather than ply based. I am not sure if you have experience laying up composite structures or not, but we also determined that a complex layup schedule like what would be produced even after using osmooth on a ply based optimization would not be wise to attempt without a laser projector, a lot of additional debulking procedures, and guidance from layup technicians with a lot of complex form experience in industry (their time is not free).

    While initially I too had planned on using the AFR, the realization that nearly the entire SES has to be completed in support of the AFR, and that there was little to be gained if the structure was only utilizating 5 or 6 different layup types (for manufacturing simplicity) led us down the SES-only path. It is my understanding that very few (if any) teams submit an AFR for monocoque cars.

    In light of this, the most efficient way to load-tailor an fsae monocoque would likely have been to focus more on using different core thicknesses and foil thicknesses rather than using too many different tape orientations and stacking sequences. This would have been less time consuming in the testing and SES submission stage, and is less confusing to the students (sleep deprived) that are placing plies in the production tool.

  3. #3
    Thank you for your response. It's very interesting to hear that few monocoque cars to your knowledge actually end up following AFR.

    I have come up with a solution that I hope we can get to pass. Otherwise we are looking at doing a very last minute switch to SES, as most of it is already done (as you mentioned would have to be if doing AFR)
    I have ended up following ASTM Standards D3039, D3518, and D6641, as well as the standard shear tests in the SES to characterize our uni, and 0/90. In addition to this we completed all of the remaining tests that the SES lays out, with the exception of 3pt bend for every single schedule being use in our chassis. Instead, we only tested 3 different sandwich panel configurations with various core thicknesses and ply schedules. We then recreated these 3 point bend tests within FEA using the data obtained from the ASTM tests stated. By comparing the results of the 'virtual' 3pt bend test to the actual, we hope to show our proficiency in analysis and testing so that we do not have to do 3 point in every direction of every schedule. Testing alone (never mind laying up all the samples) took a week straight, working 9 hour days haha.. I can't say I have attended class in a while...

    Cheers,

    Jackson

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