The longitudinal tensile behavior of carbon fibers is studied to characterize the relationship between initial stiffness and their non-linear behavior. Four different PAN-based fibers are measured through single fiber tensile testing. The results show clear non-linear behavior for all fibers, with a significant correlation between the non-linearity and the initial stiffness of the fibers. These relationships are quantified and the experiments are used to fit established models for the non-Hookean response of carbon fibers. We find a negative correlation between initial stiffness and non-linearity in the response.
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