| Περίληψη: | In the last decades, fibrous composite materials have proven to be the answer in the advanced industries' search for materials with superior mechanical properties, combined with minimized weight. Graphene, one of the current century's greatest discoveries, was quickly realized to be of immense value in this search. The inclusion of various types of graphene nanoparticles in composite structures yielded not only astounding mechanical properties, but also unprecedented improvements in the electrical, chemical and optical properties of such materials.
In the present thesis, the effect of graphene nanoplatelets (GNPs) in the fracture response of fibrous composite specimens is investigated. More specifically, nano-enhanced laminates were compared to their neat counterparts on their interlaminar fracture toughness results in Mode I and Mode II testing, under static loading. In the case of nanoenhanced specimens, two material systems were created with nanoparticles of different dimensional features, in order to further assess the effect of sizing in the overall enhancement.
The specimens for both modes originated from a single laminated CFRP plate in each case, the manufacturing of which entailed the use of an automated pre-impregnation contraption, lamination and consolidation by means of an autoclave. For the nano-enhanced epoxy matrix, the required dispersion of the GNPs was achieved by following the method of three-roll milling, that utilizes a calender configuration.
Results indicated a similar fracture response in both modes, as the nano-enhanced material system with the smaller GNPs exhibited improvement of the interlaminar fracture toughness values, by 19% for Mode I and 5% for Mode II, compared to the neat matrix system. On the contrary, the second nano-enhanced material system's results showed deterioration of the same values, 27% and 37% respectively, providing thus a strong case on the matter of the nanoparticles' dimensions effect on their capability to enhance composite material structures.
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