Fracture mechanics and damage modeling of injection molded high density polyethylene

Abstract: For many applications a fracture is a disaster, leading to failure of the application and thus its usefulness. However, when it comes to the opening of a food and beverage package, fracture is a necessity. At Tetra Pak, food and beverage packages are produced to make food safe and available everywhere. Today, many of the packages include polymer parts, such as the opening of the packages. In the technology development process, virtual engineering has become an important tool. The possibility of performing simulations may shorten the development time and increase the quality of the product. To perform simulations that are close to the real behavior of the material, the mechanical properties need to be known. At Tetra Pak®, the general knowledge of the mechanical properties of a polymer is well known by the use of tensile tests, which can be translated into a material model. However, this model is on macroscopic scale and does not include microstructure nor damage modeling. Therefore, X-ray scattering was used to further investigate the microstructure, whilst the fracture mechanical behavior has been studied by the use of tensile testing, Scanning Electron Microscopy and Digital Image Correlation. From the experimental test, it was concluded that the positioning and the direction of a crack leads to highly different fracture mechanical behavior, indicating that the anisotropy plays an important role. Furthermore, the internal layers of an injection molded polymer delaminate during tensile testing. The knowledge gained from the experiments was used to create a virtual model, including damage modeling to capture the damage behavior. The virtual model captured the overall mechanical response and damage behavior well, though further work to improve the model can be done.