A dynamic constitutive-micromechanical model to predict the strain rate-dependent mechanical behavior of carbon nanofiber/epoxy nanocomposites

Polymeric materials have wide applications; therefore, it is necessary to develop a dynamic constitutive model to investigate their strain rate-dependent mechanical behavior. In this study, mechanical behavior of neat epoxy and carbon nanofiber (CNF)/epoxy nanocomposites were studied experimentally and analytically. For this purpose, the Johnson–Cook material model has been modified to develop a generalized strain rate-dependent constitutive model to simulate the tensile and shear mechanical behaviors of the neat epoxy at a wide range of applied loading rates. The present model includes three main components: the first component expresses the elastic behavior of polymers using an empirical equation. The second component models the nonlinear behavior of polymers using the modified Johnson–Cook model. Finally, the third component predicts the ultimate strength of polymers under dynamic loading conditions using another empirical equation. Furthermore, by combining the generalized strain rate-dependent constitutive model and the modified Halpin–Tsai micromechanical model, a dynamic constitutive-micromechanical model is presented to predict the strain rate-dependent mechanical behavior of CNF/epoxy nanocomposites. To evaluate the present model, predicted results for the pure epoxy and CNF/epoxy nanocomposites were compared with conducted and available experimental data. It is shown that the present model predicts the strain rate-dependent mechanical behavior of polymeric materials with a good accuracy.