Elastic-Plastic Mixed-Mode Fracture Analysis of Polypropylene Using New Loading Device

In ductile materials the deformation can occur in the plastic zone where the crack tip deformations can no longer be considered small. Linear Elastic Fracture Mechanics (LEFM) is valid only when the inelastic deformation is small compared to the size of the crack, which called small-scale yielding. If large zones of plastic deformation spread before the crack grow, Elastic Plastic Fracture Mechanics (EPFM) must be used. There are many procedures that can be used in EPFM but still the J-integral and the Crack Tip Opening Displacement (CTOD) are generally accepted methods. J-integral is a feasible parameter for describing the fracture of the non-linear elastic materials. Arcan test fixture is widely used for mixed-mode fracture tests of the isotropic and composite materials. In this research, disadvantages of Arcan fixture such as asymmetry in in-plane loading and limitations of changing the angle of loading have been solved by designing and using a new mixed-mode in-plane loading device. Mixed-mode fracture tests from pure mode I to pure mode II were conducted on Polypropylene (PP) using elastic plastic fracture mechanics analysis. Changes of the J-integral were also investigated numerically via the finite element method for a range of loading angles.