Characterization and modeling of nonlinear viscoelastic response of PEEK resin and PEEK composites

The viscoelastic properties of PEEK resin and unidirectional PEEK composite APC-2 were characterized by an accelerated testing procedure based on the time-temperature and time-stress superposition principles. The results obtained by creep and recovery tests are presented, and the constitutive modeling of the nonlinear viscoelastic response is discussed. The stress-dependent viscoelastic responses of the composite were modeled by a special case of Schapery's nonlinear viscoelastic equation with a kernel of the general power law. The relations for the temperature-time scale shift factors and stress-time scale factors are given. With the equations and parameters presented, the linear and nonlinear viscoelastic behaviors of APC-2 composite laminate from ambient temperature up to the glass transition temperature can be described analytically. Comparisons were made on the nonlinear properties of the 15° off-axis laminate, transverse laminate and pure resin. The results agree with the theory that the matrix octahedral shear stress is the main variable determining the nonlinearity of polymers and polymer-based composites. © 1994.SCOPUS: ar.jinfo:eu-repo/semantics/publishe