An experimental study on uniaxial ratcheting of polycarbonate polymers with different molecular weights

The uniaxial ratcheting was experimentally observed on the polycarbonate (PC) polymers with different molecular weights (i.e., PC-7030PJ and PC-7020PJ) at room temperature. The effects of mean stress, stress amplitude, stress rate and peak hold-time on the ratcheting were observed. The results show that obvious ratcheting deformation occurs in the two prescribed polycarbonate polymers subjected to the stress-controlled cyclic loading; and the ratcheting strain accumulates cyclically in the direction of non-zero mean stress. The ratcheting greatly depends on the mean stress and stress amplitude, and the ratcheting strain increases more rapidly as the mean stress and stress amplitude increase. The ratcheting of two prescribed polycarbonate polymers is also significantly time-dependent, the ratcheting strains observed in the load cases with longer peak hold-time and at lower stress rate are larger than that with shorter peak hold-time and at higher stress rate. More importantly, a comparison of the ratcheting of two prescribed polycarbonate polymers shows that, at room temperature, the ratcheting of the polycarbonate polymer with a larger molecular weight (i.e., PC-7030PJ) is more remarkable than that with a smaller one (i.e., PC-7020PJ).