Fracture mechanics of PVDF polymeric material : specimen geometry effects

摘要

Polyvinylidene fluoride (PVDF) is a semi-crystalline polymer that has been widely studied for structural applications, because it exhibits good mechanical properties and chemical resistance.During viscoplastic deformation, the material whitens after the onset of necking due to nucleation and growth of voids.Mechanical tests on cracked specimens show the crack instability on DENT specimens whereas stable crack growth on SENB specimens is also encountered.In the global approach of non linear fracture mechanics framework, the two-parameter approach indicates that according to the opening stress state in the remaining ligament, the crack growth can be more or less stable.Namely, tensile crack specimens such as DENT favour instabilities whereas bending specimens (like SENB) are proved to present stable cracking.This work deals with computing Q-stresses on DENT and SENB specimens with the help of FE modelling.The material toughness J JIC IC is then determined by means of experimental data gathered with both specimens.J JIC IC depends on the specimen geometry.A J JIC IC-Q curve is then plotted for the PVDF material at 20°C.