Influence of femtolaser notch sharpening technique in the determination of essential work of fracture (EWF) parameters

The fracture behaviour of a 0.5 mm thick ethylene-propylene block copolymer is analyzed using the essential work of fracture method, using DENT-type specimens. The influence of three experimental parameters in the technique is evaluated: the effect of the notch sharpening technique, the use of a videoextensometer for monitoring the deformations and the measurement of ligament lengths before or after fracture tests were carried on. The results showed that the femtosecond pulsed laser ablation technique (femtolaser) produced sharp notches with no plastic deformation ahead of the notch tip, which yield smaller specific essential work of fracture (w(e)) values than in the cases where the notches were sharpened with razor blades. The use of a videoextensometer has allowed removing the viscoelastic energy from the plastic work, with lower values of beta w(p), The measurement of the ligament lengths before or after the test did not affect the results. (C) 2009 Elsevier Ltd. All rights reserved.