Improvement of continuous fiber reinforced epoxy based composites with nanocellulose

High-performance composites can be commonly used in marine, automotive, aerospace and defence industries. With developing technology, the properties of these materials should be improved. Nowadays, the nanocomposites, which are one kind of composite materials containing nanometer-sized inorganic nanoparticles, can be utilized to improve physical properties of polymers. The nanosized reinforcing materials, typically in the range of 1–100 nm, are uniformly dispersed in and fixed to a polymer matrix. Depending on the nanoscale dimension, nanosized reinforcing materials are categorized as one-dimensional (graphites and clays), two-dimensional (nanofibers, nanocellulose, nanotubes, or whiskers) and three-dimensional (spherical silica, metal particles, polyhedral oligomeric silsesquioxanes (POSS), and semiconductor nanoclusters). Among them, the nanocellulose, also called nanocrystalline cellulose (NCC), is a material composed of nanosized cellulose fibrils with a high aspect ratio (length to width ratio). It has been used in various high-performance products such as, composites and packaging, rheology modifiers, pharmaceuticals and cosmetics, information and communications industry. The inclusion of nanosized reinforcing materials into a polymer matrix not only dramatically improves the mechanical properties (e.g., strength, modulus and rigidity) but also reduces its flammability, heat evolution and viscosity during processing. Moreover, it brings advanced new functions in the final materials that finds applications in many industrial fields. In this work, mechanical properties of carbon and glass fiber-reinforced epoxy composites with two-dimensional (0o-90o) woven were improved by addition of nanocrystalline cellulose as reinforcing material. The mechanical properties of obtained nanocomposites were investigated in accordance with the standard tests (ISO 527-2 and ISO 178). Thermal properties of the nanocomposites were also investigated by DSC and TGA analyses. Firstly, the optimum NCC loading starting from 1% to 6% in the epoxy matrice was determined by thermal and mechanical analyses. The optimum loading was found as 4% according to thermal and mechanical tests. Then, the glass (70% w/w) and carbon (65% w/w) fibers were included in the NCC/epoxy systems. The mechanical properties of glass/NCC/epoxy and carbon/NCC/epoxy composites were investigated and the improvement between 4.4 and 27.18% were found. Thus, the small addition of NCC (4%, w/w) not only improve the mechanical properties of glass/epoxy composite but also carbon/epoxy composite. The morphology of hybrid composites was also investigated by scanning electron microscopy. Both non-hybrid (glass/epoxy or carbon/epoxy) and hybrid (glass/NCC/epoxy or carbon/NCC/epoxy) composites displayed similar microstructures in the SEM micrographs.