Fracture Mechanics on PVDF Polymeric Material : Specimen Geometry Effects (original) (raw)
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Fracture mechanics of PVDF polymeric material : specimen geometry effects
HAL (Le Centre pour la Communication Scientifique Directe), 2006
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 IC is then determined by means of experimental data gathered with both specimens. J IC depends on the specimen geometry. A J IC-Q curve is then plotted for the PVDF material at 20°C.
The Polyvinylidene fluoride (PVDF) under study is a semi-crystalline polymer that exhibits significant initial porosity and sensitivity on mechanical properties to both strain rate and temperature. A comprehensive experimental database was built in order to analyze the fracture behavior in the ductile to brittle transition domain. Experimental data on smooth and notched specimens were produced at temperature ranging from-50°C to 20°C. They were used to determine temperature dependent material parameters by using the mechanics of porous media. The obtained set of parameters was validated on two kinds of precracked specimens, by using the local approach of fracture mechanics. With the help of a finite element code, both global and local approaches of fracture mechanics were shown to complement one another: whereas classical formulae of J-integral fail to characterize crack initiation for this PVDF, the present methodology allowed the plot of J 1C values with respect to temperature.
Ecf17 Brno 2008, 2013
The Polyvinylidene fluoride (PVDF) under study is a semi-crystalline polymer that exhibits significant initial porosity and sensitivity on mechanical properties to both strain rate and temperature. A comprehensive experimental database was built in order to analyze the fracture behavior in the ductile to brittle transition domain. Experimental data on smooth and notched specimens were produced at temperature ranging from-50°C to 20°C. They were used to determine temperature dependent material parameters by using the mechanics of porous media. The obtained set of parameters was validated on two kinds of precracked specimens, by using the local approach of fracture mechanics. With the help of a finite element code, both global and local approaches of fracture mechanics were shown to complement one another: whereas classical formulae of J-integral fail to characterize crack initiation for this PVDF, the present methodology allowed the plot of J 1C values with respect to temperature.
Fracture of metal‐polymer line structures. I. Semiflexible polyimide
Journal of Applied Physics, 1994
The fracture characteristics of metal/polymer line structures formed by depositing Au/Cr lines on a semiflexible polyimide, pyromellitic dianhydride-oxydianiline (PMDA-ODA), substrate have been investigated using a stretch deformation technique. The delamination behavior, fracture morphology, fracture energy, and energy dissipation rate have been determined as a function of line width and thickness. The metal dimension was found to influence the crack formation mode and morphology. The experimental studies were supplemented by finite-element analysis to evaluate the stress distribution and deformation energetics of the line structure, which takes into account the plastic deformation of the metal and the polymer. Results from this analysis show that the observed fracture characteristics can be attributed to the edge and thickness effects induced by metal confinement. Essentially, the deformation behavior is determined by the mechanical environment induced by metal confinement at the interface. Plastic deformation of both metal and polymer plays an important role in controlling the stress distributions as well as the deformation energetics. The fracture energy of the metal-polyimide interface determined by an overall energy balance method was consistent with that obtained from energy dissipation rate. The average value is 25 J/m2 for the Au/Cr/PMDA-ODA line structure.