Influence of the Interface and the Additional Layer on the Stable Crack Propagation through Polyolefin Bilayered Structures

Abstract

In this work, model structures coextruded from polyolefin materials with different resistance against elastic and plastic deforma- tion (tensile modulus and work of deformation up to the yield point) as well as different resistance against stable crack initiation and propagation were experimentally analyzed using the multiple-specimen crack resistance (R) curve approach under quasistatic loading conditions. Additionally, numerical calculations were done using the finite element method. R curve ratios were calculated where the R curve of material 1 in the bilayer was related to the R curve of material 1 in the single-layer and so on. Depending on the mechanical performance of both layers, the additional layer highly affects the crack propagation kinetics inside the first layer when the crack propagates across the bilayered structure. Because the resistance against stable crack propagation is related to the size and shape of the plastic zone and the energy dissipated inside, the mismatch of the resistance against stable crack propagation (R curve ratios) is highly correlated to the mismatch of the resistance against plastic deformation.