Dynamic mechanical characterization for nonlinear behavior of single carbon fibers

In the work presented here, small amplitude in-situ dynamic loads are superimposed onto quasi-static tensile tests, to obtain storage and loss modulus as a function of global strain for deforming single PAN carbon fibers. This technique allows for the measurement of carbon fiber modulus at unprecedented resolution without the need for compliance correction, which is difficult to implement as carbon fibers have a non-linear modulus dependency with strain. The relationship of the elastic modulus with strain is quantified to evaluate the single fiber nonlinearity during extension. Fibers with initially higher modulus are shown to have greater nonlinear dependency on strain amplitude, even for fibers taken from the identical tow. The strong correlation between tensile modulus with strain and its initial modulus indicates that the measured mechanical properties describe a fundamental structure of carbon fibers.