CONSTITUTIVE MODELING AND EXPERIMENTAL CHARACTERIZATION OF THE NON-LINEAR STRESS-STRAIN BEHAVIOR OF UNIDIRECTIONAL CARBON-EPOXY UNDER HIGH STRAIN RATES

The mechanical response of IM7-8552 carbon epoxy was investigated for transverse tension and transverse tension / in-plane shear loadings at static and dynamic strain rates using transverse tension and off-axis tension specimens. The dynamic tests were carried out on a split-Hopkinson tension bar at axial strain rates from 113s(-1) to 300s(-1). With the already available off-axis and transverse compression test data for IM7-8552 presented in [1], a comprehensive data set is available now, which can be used for validation and calibration of numerical models. The measured axial stress-strain response was simulated using a fully 3D transversely isotropic elastic-viscoplastic constitutive model. The constitutive model represents a viscoplastic extension of the transversely-isotropic plasticity model presented in [2]. A generally quite good correlation between the measured and numerically predicted stress-strain response was achieved for all specimen types and both strain rate regimes. However, the results show the necessity to regard viscous effects in the elastic regime as well.