The purpose of this paper is to provide a peridynamic (PD) model for the prediction of the viscoelastic creep deformation and failure model. The viscoelastic characteristic consists of several stages, namely primary creep, secondary creep, tertiary creep and fracture. A nonlinear viscoelastic creep equation based on the internal state variable (ISV) theory covering four creep stages and PD equations are used. The viscoelastic equation is inserted into the PD equation to derive a PD model with two time parameters, i.e., numerical time and viscoelastic real time. The parameters of the viscoelastic equation are analyzed and optimized. A comparison between numerical and experimental data is performed to validate this PD model. The new PD model for nonlinear viscoelastic creep behavior is confirmed by an acceptable similarity between the numerical and experimental creep strain curves with an error of 15.85%. The nonlinearity of the experimental and numerical data is sufficiently similar as the error between the experimental and numerical curves of the secondary stage strain rate against the load is 21.83%. The factors for the errors are discussed and the variation of the constants in the nonlinear viscoelastic model is also investigated.

This paper presents the peridynamic (PD) numerical model for simulating a tensile test until total fracture for a brittle polymeric material namely polymethyl methacrylate (PMMA). U-notched and V-notched specimens were used to investigate the effect of the notches on the elongation and fracture of PMMA. The tensile elongation of PMMA exhibits nonlinearity with respect to the applied load, while the fracture occurs when the material stress has reached the ultimate tensile stress of the material. Similar elongation and fracture properties were applied on PD simulations. Two types of elongation equation are used namely brittle and ductile equations to form PD-brittle and PD-ductile models. The published experimental data of tensile fracture test on notched PMMA specimens are used as reference to validate the simulations of the PD models. The PD numerical force-extension curves have good quantitative similarity for V-notched specimen but adequate quantitative similarity for U-notched specimen. As for the quality of the fractured specimen shape, the PD simulations have good similarity for the V-notched specimen but adequate similarity for the U-notched specimen. The plot of the internal force distribution from the simulations of PD shows good qualitative similarity to the plot of the stress distribution from the published data of FEM in terms of stress concentration. From the PD results, it is observed that the PD-ductile model has better capability in producing accurate simulation of the notched specimens than the PD-brittle model.