Further development of a data reduction method for the nonlinear viscoelastic characterization of FRPs

According to the well-known Schapery's formulation, the nonlinear viscoelas tic response of any material is controlled by four stress and temperature d ependent parameters, g(0) g(1), g(2) and a(sigma), which reflect the deviat ion from the linear viscoelastic response. Based on Schapery's formulation, a new methodology for the separate estimation of the three out of four non linear viscoelastic parameters, g(0), g(1) and a(sigma), was recently devel oped by the authors. In the present article, a further development of the p reviously developed methodology is attempted leading to an analytical estim ation of the fourth nonlinear parameter, g(2), which additionally includes the viscoplastic response of the system. Thus, a full nonlinear characteriz ation of the composite system under consideration is achieved. The validity of the integrated model was verified through creep-recovery experiments, a pplied at different stress levels to a unidirectional carbon fibre reinforc ed polymer. (C) 1999 Elsevier Science Ltd. All rights reserved.