Mechanical Characterization of Linen Fibers: The Turin Shroud Dating

As the 1988 radiocarbon dating of the Turin Shroud (TS) was debatable also from a statistical point of view, new dating methods have been proposed. This paper presents the result of an improved mechanical dating. A recent cyclic-load machine has been improved to better fix fibers under test by using a special support designed for the purpose. The mechanical behavior of linen fibers of three different ages are measured and compared discussing these results in reference to the complex structure of aged linen fibers; the three samples are a linen fiber from an Egyptian mummy of 27thCentury B.C.; a linen fiber coming from the TS, and a recent linen fiber. This machine allowed to confirm the previous results regarding the TS mechanical dating, showing that these results are again compatible with the First Century A.D., the period in which Jesus Christ lived in Palestine. The improved machine also showed that the complex nonlinear behavior of the fibers is also due to the packing of the Secondary Cell Wall of the linen fibers, mostly composed of micro fibrils, that produces a memory-effect. The stiffening of the linen fibers with the loading increasing is a property detected for all the tested fibers that must not be forgotten also in the construction of flax fibers based composites.