I'm planning an experiment with ISO 527. I would like to know what the difference are when testing a type A ( with narrow parallel-sided section and tabs) compared to a type B (rectangular shaped) test specimen. I'm also planning to conduct a ISO 178 flexural strength test and therefore it seems appropriate to choose type B, since the dimensions for type B in ISO 527 and ISO 178 are the same.
Dear Jonas,
The tests of ISO 527 and ISO 178 are good tests for quality control in factory (FPC in European jargon). Those tests might not be always appropriate for other purposes (model development; characterization of design properties of products;...), because of different side effects, if you are not aware of these.
The choice of the specimen shape is dictated by the polymer type (stiffness / strength) and the homogeneity/heterogenity / isotropic character of the tested product, and of the thickness of the specimen : basically, in function of the usable cutting tools, and in function of the expected/known behaviour of the material. The dumbell shape (type A) is usually punched out of a plate if the product is soft/thin enough; a cutting is possible, to check with the labo. A cutting/sawing of a dumbell shape is more work intensive, and not always possible (strength cutting tools), nor wishable (loss of representativity of the tested specimens for the intended purpose); in that case the type B is an option. The interest of the dumbell shape (or dogbone shape) is to force the breakage/necking of the specimens within its gauge length : if the breakage occurs outside the gauge length, then the result should be disregarded.
The dumbell shape specimen gives little interest for a flexural test as the one described in ISO 178.
A major point of attention is that mechanical properties of polymers are rather to be understood as product than material properties, that means influence of processing conditions and of experimental uncertainties can play an important role on the results.
I only can advise you to consult following book, which is a kind of proposed "meeting point" between academic research and industrial development, written by experts having been involved in standardization works for polymer products :
Moore, D. R., and Turner, S. (2001). Mechanical evaluation strategies for plastics. Woodhead Publishing Ltd, Cambridge
My personal advise : dare to work iterative with small experimental campaigns. A practical example here : http://hdl.handle.net/1854/LU-4346098.
Good luck.
Great advice Didier Delincé ! Bridging the gap between academic research and industrial development is something I have been contemplating myself lately. I will study the book and your work further. Thank you!
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