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Sep 25

Swimming pool analysis

No we cannot CT scan your whole swimming pool, not non-destructively anyway. What we can do is take a sample of fibreglass from where the weir is cut out, and analyze that section. In this example, two samples of different fibreglass pool manufacturing methods are compared. These are the chopper gun application (sample 1) and the hand lamination method (sample 2). We do not endorse one or the other and have done a comparison based on one sample of each, but the newly installed pool shown is of the chopper gun application type. The chopper gun sample has a lower average porosity while the hand lamination method has a higher average porosity as well as larger pores in general. In this project, large sections were scanned followed by a high resolution scan of small sections to see more details.

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pool samples

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histogram 20mm samples swimming pool

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VIDEOS:
ROTATION OF POROSITY COMPARISON: Rotation
SLICE VIDEO: SLICE MOVIE POOL

2 comments

  1. Alberto Tagliaro

    Hi Dr Du Plessis,
    Any comment regarding relative tensile strengths of these two samples. What effect does increased porosity have on the strength of a pool shell – presumably it weakens it?

    Overall, I would assume that hand lamination produces a stronger shell relative to chopper gun because of the length of glass fibers and the fact that they are in mats, with some reduction in strength due to porosity.

    Regards,
    Alberto.

    Ps/ just an interested person, not involved in pool manufacturing!!

    1. Dr Anton du Plessis

      Hi Alberto
      You are right, porosity will weaken the material, but there are many other factors also involved. We also only scanned one sample of each, this is not representative enough to make any conclusions yet. It is a nice example though and the largest pores are expected to cause some serious issues (largest one being about 6 mm wide and 2 mm thick in a approx 6-8 mm thick shell!), compared to the same material with no pores. Anyone interested in a more serious study into this topic is welcome to contact me, I will be very interested to extend this and to see what the major factors are affecting the strength of these materials and to compare them, via CT scans, simulation and validation with tensile and other tests. We have in situ tensile testing as well, which means we can see the material deformation in a CT scan when a load is applied, to see exactly where in the material it first fails, ie the weakest point.
      Thanks for the interest

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