Essential Work of Fracture (EWF) of multilayer films

The potential of a fracture mechanics approach (Essential Work of Fracture or EWF method) to determine the toughness of PE/PEgMAH/PA multilayer films has been investigated. The films had been modified either by blending EVA in the PE and PEgMAH layers or by inserting clay nanoparticles in the PA layer. The method was first calibrated on PE and PA single layer films. An analysis of the sensitivity of the toughness, assessed by the EWF method, to both sample geometry and test conditions has been carried out, so as to optimise the testing procedure for these materials. Then these optimal test conditions have been used to characterise PE- and PA-based multilayer films. The results show that the Essential Work of Fracture method is relevant for this type of structure, and may be more sensitive to the film composition variations than standard tensile mechanical tests, especially when the composition modification affects the layer of lowest rigidity and tensile strength.