The code stated that:-
"The initial loading rate up to deflection of L/900 for other sizes and shapes of specimens shall be based on reaching the first-peak deflection 40 to 100 s after the start of the test"
It does not specify the speed rate of the loading. Does that mean i can simply "pick" the rate of loading and test it on the specimen until the first peak deflection (as i understand, this is the first crack) is within 40 to 100s after the test?
It is important to distinguish between whether you are using a load rate control (i.e. XX kN/s) or deflection rate control (i.e. XX mm/s), You should be using deflection rate control if you are interested in 'post peak' (i.e. secondary or residual toughness provided by the fibres) parameters; the nature of a load-rate controlled test means that it will not correctly characterise the toughness after the first crack strength has been passed because the test machine will accelerate the cross-head in order to try to keep the loading rate constant.
You will need to make an estimate of the deflection at 'first peak' failure for your specimen, and divide this by 40s (for the upper bound) or 100s (for the lower bound) to derive a suitable deflection rate. If it is not possible to predict the deflection at failure, it would be useful to look at the literature to see what loading rates have been used for similar specimens.
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