Ricerc@Sapienza

In an attempt to increase the low-velocity impact response of natural fiber composites, a new hybrid intraply woven fabric based on flax and basalt fibers has been used to manufacture laminates with both thermoplastic and thermoset matrices. The matrix type (epoxy or polypropylene (PP) with or without a maleated coupling agent) significantly affected the absorbed energy and the damage mechanisms. The absorbed energy at perforation for PP-based composites was 90% and 50% higher than that of epoxy and compatibilized PP composites, respectively.

Four different strategies for mitigating the highly hydrophilic nature of flax fibers were investigated with a view to increase their compatibility with apolar polypropylene. The effects of two carbon nanostructures (graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs)), of a chemical modification with a fatty acid (stearic acid), and of maleated polypropylene on interfacial adhesion, mechanical properties (tensile and flexural), and thermal stability (TGA) were compared.

The unremitting quest of natural and renewable materials able to replace their synthetic counterparts in high-performance applications has involved also sandwich structures. In this regard, the aim of this work is to characterize the impact response, in both high- and low-velocity conditions, of green sandwich structures made of agglomerated cork as core and flax/epoxy laminates as face sheets. Both bare cork, flax skins, and complete sandwich structures were subjected to impacts at three different energy levels representing the 25%, 50%, and 75% of the respective perforation thresholds.

The present work investigates the effects of an environmentally friendly treatment based on supercritical carbon dioxide (scCO2) on the interfacial adhesion of flax fibers with thermoset matrices. In particular, the influence of this green treatment on the mechanical (by single yarn tensile test), thermal (by TGA), and chemical (by FT-IR) properties of commercially available flax yarns was preliminary addressed.