Fracture Mechanics Applied in Thin Ductile Packaging Materials-Experiments with Simulations

Abstract: Finding new or improving existing opening solutions for a package are important at Tetra Pak since the development of new polymers films influence the present package opening solutions. Knowing the general mechanical and fractural behavior of the package material is crucial for the understanding and prediction of the overall opening performance. This thesis presents a study of two different polymer materials, Polypropylene (BoPP) and Low-density polyethylene (LDPE). Single layer of BoPP, single layer of LDPE, BoPP with both sides laminated by LDPE with full adhesion(LDPE/BoPP/LDPE) and with no adhesion(LDPE//BoPP//LDPE) are analyzed under Mode I tensile loading. The study is based on physical test together with Finite Element analysis using computer software ABAQUS. The physical test and calibration is done for continuum and fractured (center crack) test specimen. Comparison of the physical test and the numerical analysis showed a convincing match between the two results for every test cases, continuum and fracture, both in machine and cross direction. Fracture toughness calculated using theory of linear elastic fracture mechanics (LEFM), Modified Strip yield model (MSYM) and Experimental test (using global force) and all compared together to determine the possible range of the fracture toughness of BoPP and LDPE.