Verificação da sensibilidade do método do Trabalho Essencial de Fratura (EWF) a taxa de deformação, aplicado ao polietileno de alta densidade

Abstract

Polyethylene is a semi crystalline viscoelastic and thermoplastic polymer widely used in a variety of products and applications. The increasing employment of this material in structural responsibility applications implies a deeply characterization of its properties. In this work, the application of the EWF method to a high density polyethylene developed for blow-molding processes is studied by varying the speed of the test. Considering the dispersion of the results, it was not possible to observe the sensitivity of the essential work of fracture (we) to the rate of deformation in the speed range adopted. The results obtained from the non-essencial fracture work (βwp) suggests that this parameter decreases with the loading rate. The Ramp Test was also applied to the studied material obtaining a stress characteristic value of 9,8 MPa, which is comparable to previous results. However, it was not possible to estabilish a correlation between the results of the Ramp test to those of the EWF test, probably due the plane stress state developed in the region of the tip of the crack.