Physical assessment of essential work of fracture parameters based on m-LLDPE blown films

- Three distinct fracture process zones have been identified in blown film fracture.
- Viscoelastic component should be included when estimating total fracture energy.
- Essential work of fracture is related to the volume of inner fracture process zone.

A new experimental approach based on essential work of fracture (EWF) method and an in-situ digital image correlation strain mapping analysis has been developed to quantify different aspects of fracture energy on model metallocene linear low-density polyethylene (m-LLDPE) blown films. Three distinctive fracture process zones have been identified from the photoelastic observation of the model m-LLDPE blown films. These three zones include the essential work (We) zone due to necking and crack propagation, the non-essential plastic deformation zone (Wp), and a newly proposed recoverable viscoelastic deformation zone (Wv), which is found to be nontrivial. Furthermore, in contrast to the assumption involved in the EWF theory, We is found to be proportional to the volume of the materials involved in the inner fracture process zone. The current approach allows for exact physical interpretation of the EWF parameters and their correlation to material characteristics. Usefulness of the present work for development of stronger polymeric blown films is discussed.

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