In-plane bi-axial testing of thin paper

Abstract: During its lifetime, a beverage package is subjected to a complex loading history where the loading, in general, is multiaxial. Hence, to optimize the performance of the package, knowledge of the material’s anisotropic multi-axial deformation and subsequent failure is necessary. This report presents a way to investigate the anisotropic loading and fracture of thin paper using bi-axial testing and to analyse the bi-axial test using the Finite Element Method. Getting thin paper to fracture in the central region, where the deformation and loading are bi-axial, proved difficult. To overcome this challenge, a new bi-axial specimen, with a specific sample preparation technique, is proposed and implemented in this specific project. This cruciform-shaped thin paper specimen was reinforced with laminating plastic everywhere but in the central region. This was done to avoid material failure in the notched radius area or the clamps, rather to facilitate a material failure in the central region of the material specimen. In order to simulate the bi-axial test, a Hill elastic-plastic material model was calibrated, and the material parameters were obtained from uniaxial tensile tests. When subjected to bi-axial loading, the proposed cruciform-shaped specimen fractured systematically and repetitively for the different load cases studied. Moreover, the Hill material model captured the force vs. displacement curve from the experimental results well but overestimated its values. The overestimation was mainly due to sliding during the experimental tests.