... | ... | @@ -31,6 +31,7 @@ Molding urethane samples |
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A second method consist in directly molding your sample in the shape you want. In this case you need first to make a mold of the sample shape you want. Then, you pick urethane with the Young Modulus corresponding with the load you want to apply and finally you can cast the liquid urethane and get your sample. The complete method and tips are given in [this tutorial](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/molding-urethane). This is the most versatile way to make sample since you can make the shape you want as long as you can make a mold, and you can easily tune the stiffness of the sample varying the cross-linker quantity. Also it is a very cheap way to make very clean photoelastic samples since raw urethane is not expensive at all.
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![100_4746](uploads/4ac6d6f7f55264d8e784cc0ab8c94f0b/100_4746.JPG)
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Squeezed piece of urethane between crossed polarisers.
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... | ... | @@ -41,11 +42,13 @@ Not only plastic polymers are good photoelastic materials convenient to mold. So |
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* Gelatine for example have been used in different labs by [lim *et al.*](https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.119.184501), [Kilcast *et al.*](http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2621.1984.tb12494.x/full) and [Workamp and Dijksman](https://arxiv.org/abs/1709.10311). This material is very clear, easy to make and to mold and nicely photoelastic but not very stable on the long run even if it can be cross-linked for a better stability as explained [here](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/molding-gel#making-cross-linked-gelatin-discs).
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![100_4737](uploads/02aecc17f3d266b6cef29cf415ee74f5/100_4737.JPG)
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Squeezed piece of gelatine between crossed polarisers.
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* Agar-agar gel can be used as a photoelastic material too, just like [Tamlinson and Taylor](https://www.spiedigitallibrary.org/journals/Optical-Engineering/volume-54/issue-8/081208/Photoelastic-materials-and-methods-for-tissue-biomechanics-applications/10.1117/1.OE.54.8.081208.short) did. Just like gelatine, it is easy to make and to mold and quite nicely photoelastic. However it is not perfectly transparent and the material is quite brittle when loaded dynamically and plastic-like when loaded very slowly.
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![100_4735](uploads/76da575d21ad6d75f25052769f041474/100_4735.JPG)
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Squeezed agar gel of urethane between crossed polarisers.
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* Many other biologic or synthesized gels like konjac...
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... | ... | @@ -56,6 +59,6 @@ The different methods associated with these different materials are explained in |
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Printing polymer samples
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Even if the method is just at its beginning it is also to 3D print photoelastic samples. Stratasys permits for example to print VeroClear (read [this article](https://www.researchgate.net/publication/319528019_The_mechanical_and_photoelastic_properties_of_3D_printable_stress-visualized_materials_OPEN) for more details).
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Even if the method is just at its beginning it is also possible to 3D print photoelastic samples. Stratasys propose for example to print VeroClear a transparent polymer that has a quite good photoelastic response (read [this article](https://www.researchgate.net/publication/319528019_The_mechanical_and_photoelastic_properties_of_3D_printable_stress-visualized_materials_OPEN) for more details). Just like polyurethane molding, this method is very versatile. However if not properly used it let massive residual stresses. More details are avaiable [here](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/3D-printing)
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[<go back to home](https://git-xen.lmgc.univ-montp2.fr/PhotoElasticity/Main/wikis/home) |
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