I want to characterize the mechanical properties of individual basalt fibers. I am having problems when choosing a test speed. If a follow ASTM C1557, I should choose a speed where the fiber fractures in less than 30 seconds. But if I follow ISO 5079:2020, my speed should be 50% gauge length per minute for specimens with a mean elongation at break lower than 8% (as is the case for basalt fibers). In this case, for a gauge length of 20mm, I would use 10 mm/min speed, which will break the fiber in less than 3 seconds.
Could you advice me in which speed to choose, please? Thanks in advance!
I come from an engineering mechanics background, but I am rusty.
Three seconds is definitely less than 30 seconds. I suppose the ASTM test is setting the time to avoid creep, and you will definitely avoid creep at that faster speed. I do not know what the ISO spec is trying to achieve.
I would read the prefaces to the techniques to make sure they apply. There is a danger of applying a standard outside its intended scope.
Rate of loading influences the peak load. Your effort is to understand the material behaviour under tensile stress. Please study the stress/strain graph of the basalt fibre. Select the test speed yielding higher values by conducting tests at various speeds. Standards are for reference. Tests parameters are material specific.
Thank you, Britannia Vondrasek,University of Utah.
Hope my view is useful to Susana Garcia-Mayo, KU Leuven.
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