Refined fixture design for effective essential work of fracture toughness characterization of m-LLDPE thin films

Characterization of Mode-I fracture toughness of ductile polymeric thin films is nontrivial. Proper specimen preparation and experimental procedures are required to ensure in-plane tensile loading. In this study, a custom-built double-edge notched tensile test fixture was employed to characterize the Mode-I essential work of fracture (EWF) toughness of metallocene linear low-density polyethylene (m-LLDPE) films. Effects of specimen geometry, strain rate and film orientation on the specific essential work of fracture, we, and the specific non-essential work of fracture, wp, were investigated. Results indicate both EWF parameters are independent of the crosshead speed, gauge length (distance between upper and lower clamps) and specimen width within the ranges tested. we is significantly higher for thinner films and for crack propagation perpendicular to the blown film machine direction (MD). The usefulness of EWF for evaluating m-LLDPE fracture toughness is discussed.