Deformation Mechanics of a Non-linear Hyper-viscoelastic Porous Material, Part I: Testing and Constitutive Modeling of Non-porous Polychloroprene

Solid and foamed polymeric materials demonstrate a significant increase in stiffness with increasing deformation rate, and existing hyper-viscoelastic constitutive formulations are often limited in applicability across large ranges of deformation rate and finite deformations. The development of micro-level pore-based foam models requires the mechanical properties of the constituent non-porous material coupled with efficient and representative constitutive models. In this study, the mechanical properties of non-porous polychloroprene were measured at low deformation rates using a conventional hydraulic test apparatus and at high deformation rates using a polymeric split Hopkinson pressure bar apparatus. A constitutive model was developed using an additive formulation to describe the hyper-viscoelastic material response for large deformations and a range of deformation rates from quasi-static (0.001 s −1 ) up to 2700 s −1 . The material coefficients were determined using a constrained optimization technique that simultaneously fit all of the data, and iterated to determine the required number of material constants. The constitutive model was implemented into an explicit finite element code and accurately predicted the response of non-porous polychloroprene rubber (R 2 = 0.996) over the range of tested strain rates. Importantly, the finite element implementation minimized the required computational storage, addressing limitations in existing constitutive models, and was computationally efficient, which was necessary for the large finite element micro-scale simulations of foamed polychloroprene undertaken in a follow-on study.