| The performance of a composite material is dictated to a large extent by the properties of the interface/interphase that exists at the boundary between the constituents of the composite. Therefore, controlling the properties of the interfacial region is an essential requirement in order to improve the overall performance of the composite. The main objectives of this research are: (i) to improve the interfacial bonding in fibrous composites in order to enhance the load transfer from the matrix to the fibers; (ii) to improve the impact tolerance of brittle composites through the addition of plasma-treated energy absorbing interleaf material within the lamina layers; and (iii) to study the effect of interphase properties on the stress concentration phenomenon in multifilament composites.; In this research, RF-plasma technology is used as a powerful tool to tailor the properties of the composite interphase. Argon plasma treatment was used to increase the surface roughness, surface wettability and to facilitate the grafting of plasma polymer layer onto the substrate surface. Ammonia plasma was also used to introduce nitrogen containing functionalities onto the surface without creating a thick interphase. In addition, different plasma polymerized coatings were applied to tailor the interphase properties.; Different interfacial testing techniques were used to investigate the effect of interfacial properties on the micromechanical behavior of single fiber composites. The techniques used in this study included the fragmentation test, the pull-out test and the state of the art micro-Raman spectroscopy technique.; The results showed that RF-plasma is a powerful technique to modify the interfacial properties in composite with minimal adverse effects on the bulk properties of the substrate compared to other conventional surface modification techniques. The impact properties of interleaved composites can be improved by controlling the interfacial adhesion between the interleaf and composite lamina. The properties of the interphase can be tailored to control the stress concentration phenomenon in multifiber composites, which in turns, controls the strength and toughness of the composite. |
