Separation of tear energy of polythylene blown films using essential work of energy

• EWF test give two different information, EWF and NEWF (or slope) for crack behavior • Load-displacement curves obtained by DENT specimen are similar as ligament increase • EWF is the intrinsic material parameter for given thickness, and is corresponding to the J_Ic based on mathematical similarity • Slope of EWF test gives the reduction of compliance during crack propagation, NEWF is the concentration of energy dissipation • All CD crack propagation and MD crack propagation of 0.920 density films, consistent shape ratio (Beta) of PZ and ligament • For MD crack propagation of 0.940 density films, there is no craze zone observed in the vicinity of crack propagation (Zero beta) • The accuracy of EWF test (R-square) have the same trend with Elmendorf tear test (CV), and it may depends on geometry of the specimen, process condition, notch symmetry and so on • Although EWF value is important to explain the intrinsic fracture toughness of the material, actual energy consumption including crack propagation is controlled by NEWF and beta as ligament increase • EWF value of CD crack is larger than that of MD crack for 0.920 density films, but opposite trend for 0.940 density films observed • Good correlation between slope and Elmendorf tear is observed in semi-log scale for all films • Though there are some differences of EWF observed for tested films, EWFs for yield for films with similar density are similar each other. Slope for yield shows weak ligament dependency • By separation of work of energy, most energy dissipation mechanism is observed at NEWF which is represented by slope, which may be microcrazing and/or microvoiding • Steps of films with plane stress responding for EWF test are elastic stretching, yielding with large notch blunting, ligament drawing, stretching and necking of drawn material, instability with thinning of ligament.