For the compressive strenghth, you haver to prepare your samples while taking into account that the height equal to twice the diameter as is mentionned in the Afnor Standard NF P 94 420 (see the attached file).
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Thank you very much for your answer. This is not a normal metallic material .. this is a composite sandwich structure material where the sample cross section will in the range from 1 square inch to 9 square inch as listed in the ASTM standard.
I couldn't find any attached file you are referring to (Afnor Standard NF P 94 420)