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Elloumi A.,LAboratoire des Systemes Electro Mecaniques LASEM | Elloumi A.,University of Sfax | Pimbert S.,University of Southern Brittany | Bradai C.,LAboratoire des Systemes Electro Mecaniques LASEM | Bradai C.,University of Sfax
Polymer Engineering and Science | Year: 2015

Calcium carbonate (CaCO3) reinforced polypropylene/ethylene propylene rubber (PP/EPR) copolymer composites for automotive use were developed by means of extrusion and injection molding process. Three kinds of CaCO3 (stearic acid treated and untreated) nanoparticles and microparticles were used as fillers. The influence of stearic acid, particle size, and filler content on the state distribution and morphology were investigated by SEM and rheological measurements. Two different morphologies were observed: EPR and CaCO3 dispersed in the PP matrix and a core shell structure, depending on the interactions between EPR and CaCO3. Toughening mechanisms and mechanical properties of the different systems were investigated. Significant improvement in tensile modulus is observed in all composites, depending on filler content. Elongation and notched impact strength were drastically decreased, especially for composites with nano CaCO3. Better impact properties were obtained with low content of treated particles, showing the importance of filler treatment. © 2015 Society of Plastics Engineers.

Mnif R.,Laboratoire des Systemes Electro mecaniques LASEM | Elleuch R.,Laboratoire des Systemes Electro mecaniques LASEM | Halouani F.,Laboratoire des Systemes Electro mecaniques LASEM
Materials and Design | Year: 2010

Many practical structural members and parts may be subjected to fluctuating plastic deformation by prestraining due to manufacturing and machining process (forming operation, straightening, etc.) and unintentional overstrains (misuse, accidents, under design, etc.). For this reason, the effect of the prestrain and periodic overstrains on fatigue life and damage behavior was being necessary considered for reasonable fatigue design. In this context, an experimental program was conducted to study the effects of overstrain and prestraining on fatigue life and damage behavior of brass alloy subjected to cyclic torsional loading. To establish baseline fatigue behavior, several virgin specimens were tested under fully-reversed strain control and constant amplitude fatigue torsional loading up to failure. The obtained experimental results showed that the fatigue life depends strongly on the strain amplitude and prestraining type (monotonic or cyclic). In addition, a beneficial effect in the fatigue life was observed for all tests with periodic overstrain. Cyclic fatigue fracture on a macroscopic scale revealed features reminiscent of locally ductile and brittle mechanisms. At the same time, microscopic analysis indicated a difference on fatigue fracture surface morphology between the conducted tests and those performed under constant amplitude loading. © 2010 Elsevier Ltd.

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