As a bibliographic research has shown the absence of machines of the type requested, it has been necessary to design, build and test a new cycling-loads machine capable to measure the micro-mechanical characteristics of flax fibers like Young modulus, tensile strength and the loss factor. The flax fibers in question have diameters of 5-25 μm and lengths of 1-3 mm.
The requirements for the testing machine are to furnish the stress-strain parameters, with an uncertainty not greater than 10%, relative to different loading-unloading cycles measuring fibers from 1 mm to 30 mm long, with 1% strain, a resolution of the order of 0.1 μm and capable to measure forces up to 0.5 N with a resolution better than 2 μN.
The design problems have been solved by employing a mechanical lever displaced by a micrometric screw to impose the displacements and by using an analytical balance, properly calibrated to measure the corresponding forces. The single flax fibers have been glued on particular polyester bases build up for the purpose.
The machine has been used to date fibers coming from the Turin Shroud. To reach this purpose, proper calibration curves have been determined using a series of ancient flax textiles. The Turin Shroud fibers resulted of 400 AD with an uncertainty of ±400 years at 95% confidence level, thus compatible with the epoch in which Jesus Christ lived in Palestine.
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