For the past many years, packaging have been designed just to preserve food items and to catch the attention of the customers by concentrating on the design rather than making it easy to open. But now companies like Tetra Pak are focusing on the flexibility of packaging design by making it user friendly without compromising the design quality. To predict the overall opening performance, it is required to understand the general mechanical and fracture behavior of a material. This research project focused on the study of two polymer materials, Poly Propylene (PP) and High Density Poly Ethylene (HDPE) which are used to manufacture screw caps of the food packaging. Further fracture study will enable to understand how the material will behave under shear opening. Physical experiments were performed on both materials for finding Tensile and Shear properties of the material. Dog bone shape for the case of continuum, 1mm and 2mm centered crack have been tested under Mode I loading, and tensile material model for Abaqus was constructed. Properties i.e. fracture toughness and energy release rate was determined for both of the materials by using Modified Strip Yield Model (MSYM).