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Fracture toughness indentation experiments performed on Si-alloyed LTI PyC-graphite layered
composites for biomedical applications have allowed to fully assess the sequence of damages induced in
the top pyrolytic carbon layer while increasing the applied load. FEM analysis has indicated a
compressive residual stress pattern in PyC. Kc data obtained at different applied loads pertain to
composites with a different residual stress level, what is the cause of the large scatter usually found in Kc
values while performing such a type of experiments. A procedure to single out a unique Kc value for
heart-valve screening and design purposes is illustrated.