Sharlin Shahid

An experimental characterization of the mechanical properties in a low-density polyethylene (LDPE) film is performed in this article. Anisotropy in LDPE at different in-plane material orientations is measured from the stress–strain response and digital image correlation observations of the specimens under uniaxial tension. Finite element simulation of in-plane anisotropy of the material is carried out in Abaqus R2020 using available models like von Mises, Hill 48, Barlat Yld91, and Barlat Yld2004-18P. To express the mechanical behavior at larger strain, a suitable hardening extrapolation model is selected from a trial of several extrapolation models. To validate the simulation methods and the material characterization process, finite element simulation results such as force displacement and strain distribution are compared with the experimental data showing good agreement. Finally, a calibrated anisotropic yield model together with ductile failure criterion is shown to successfully simulate the response of precracked LDPE film under tension. Overall, this study provides valuable insights into the modeling of LDPE polymer films with and without cracks using different anisotropic yield functions and largely simplifies material characterization with some tradeoffs.

Injection-molded polyethylene plates exhibit highly anisotropic mechanical behavior due to, e.g., the uneven orientation of the polymer chains during the molding process and the differential cooling, especially in the thickness direction. Elastoplastic finite element modeling of these plates in particular is used with isotropic yield criteria like von Mises, trading off accuracy in favor of simpler constitutive characterization and faster solution. This article studies three different anisotropic yield criteria, namely, Hill 1948, Barlat Yld91, and Barlat Yld2004-18P, for the finite element modeling of low-density polyethylene (LDPE) at large uniaxial tensile deformation and compares the accuracy and computation time with von Mises. A simplified calibration technique is investigated to identify the constitutive parameters of the studied Barlat group yield criteria. The calibration process is simplified in the sense that only uniaxial tensile tests with digital image correlation measurements are used for the calibration of all the yield criteria studied in this article, although a standard calibration procedure for the Barlat group yield criteria requires additional material testing using more demanding test setups. It is concluded that both Barlat Yld91 and Barlat Yld2004-18P yield criteria can be calibrated with only a few tensile tests and still capture anisotropy in deformation–stress–strain at different levels of accuracy.