Development of advanced composites with tailored strength and toughness.

The main activity of these 3 years of PhD, is the evaluation of interfacial shear strength in biopolymer composites; analytical models were used to verify their applicability to this new class of materials. In many cases modifications at these analytical models were made to better taking into account the specific features of the reinforcement and of the polymeric matrix; in some cases, also micromechanical deformation processes were investigated. Different types of biocomposites systems were studied. As a consequence, different preparation methodologies, experimental conditions, measurement methods were adopted during these three years of activities. The evolution of the reinforcement as a function of aspect ratio was progressively studied; this aspect is fundamental because the evaluation of the IFSS and consequently the final mechanical properties are strongly influenced by the aspect ratio. Also the micromechanical deformation processes (debonding, fibers’ pull-out, cavitation, fiber breakage etc…) were investigated. The activities of this PhD work can be divided into three sections: 1) Evaluation of interfacial shear strength (IFSS) of PLA/ PC blends containing cellulosic fibers having a relatively high aspect ratio (≃ 36). 2) Flax fibers characterization and evaluation of mechanical properties and IFSS of PLA-Flax composites containing short fibers (aspect ratio < 10). 3) Study of the rigid filler toughening mechanism in PLA-Calcium Carbonate composites (aspect ratio ≃1).