2019 年 85 巻 874 号 p. 19-00058
With use of the numerical material testing (NMT) approach based on homogenization theory, a time-temperature reduction law is proposed for both relaxation and elastic properties in the orthotropic viscoelastic constitutive equation, which is supposed to represent the macroscopic material behavior of unidirectional fiber reinforced thermoplastics (FRTP) under various temperature environments. We start with dynamic viscoelastic measurements for polycarbonate (PC) under different ambient temperatures to evaluate the master curves of storage and loss moduli as well as loss tangent that exhibit the temperature- and time-dependent characteristics of its relaxation and elastic properties. Then, with the use of the obtained viscoelastic properties of the resin, a series of NMTs simulating macroscopic stress relaxation are conducted on a periodic microstructure (unit cell) model of the FRTP to characterize the macroscopic viscoelastic material behavior. Finally, the shift functions of the orthotropic relaxation and elastic properties in the assumed macroscopic viscoelastic constitutive law involving the proposed time-temperature reduction law are determined to clarify its time- and temperature-dependent characteristics.
