| Nanocomposites have been widely studied because of their unique properties, such as mechanical, tribological, electrical, thermal and optical properties. So the fabric composites based on these nanocomposites not only have high specific strength, wear resistance and thermal resistance, but have those unique properties of nanocomposites. In this paper, several nanofillers were chosen (such as nanosilica, nanoalumina, attapulgite and carbon nanofiber) as fillers to modify polymer matrix (including polyoxymethylene thermoplastic and epoxy resin thermoset), and various preparation methods (eg. in-situ polymerization, mechanical blending and solution casting) were used to prepare the nanocomposites. The mechanical, tribological and electrical properties of the nanocomposites were studied. Furthermore, fabric nanocomposites were made by hand lay-up process with nanocomposites as matrix and polyester fabric as fabric reinforcement to study their mechanical and tribological properties. The detailed research contents and results are summarized as follows:1. Nanosilica/acetal copolymer nanocomposite was prepared by in-situ bulk cationic copolymerizaiton of trioxane and 1,3-dioxolane at the presence of nanosilica. It was found that nanoparticles had good compatibility with acetal copolymer and had an average size of about 100nm. The high surface energy and small scale of nanoparticles had a prominent impact on the polymerization mechanism. For the crystallization behavior:On one hand, nanoparticles acted as nucleation center, which accelerated the crystallization rate but reduced the crystallinity. The spherulite sizes also decreased with the addition of nanoparticles attributed to the nucleation effect. On the other hand, the presence of nanoparticles interrupted the spherical symmetry of the crystallite.2. POM nanocomposites with various contents of nano-Al2O3 were prepared by twin-screw extruder in order to study the influence of inorganic nanoparticles on tribological properties of POM nanocomposites under dry sliding and oil lubricated conditions respectively. The results showed that nanoparticles were more effective in enhancing the tribological properties of POM nanocomposites in oil lubrication tests than in dry sliding tests. The reason may be attributed to the flowability of lubrication oils, which broadened the activity range of nanoparticles. The nanoparticles peeling off from the worn surface could fill in the roughness of the counterpart and the wear scratches due to their small sizes and high surface energy. As a result a uniform and compact transfer film was formed on the surface of counterpart steel ring, which was effective in protecting the surface from the abrasion of hard asperities on counterpart surface accounting for the reduction of friction coefficient and wear volume. However, nanoparticles peeling off from the worn surface agglomerated under dry sliding condition. They resided between the friction surfaces accelerating the abrasive wear. The optimal nanoparticles content in POM nanocomposites is 9 wt% at which the nanocomposite had the lowest friction coefficient and wear volume at the same time. The friction coefficient of POM nanocomposites decreased with increasing load under relatively lower load, and reached the lowest value under load of 245N, then increased with the increasing load. However, the wear volume loss of POM nanocomposites increased with the increasing load.3. POM composites modified with nanoparticles, polytetrafluoroethylene (PTFE) and MoS2 were prepared by a twin-screw extruder. It was found that POM/PTFE/MoS2/Al2O3 nanocomposite had the best mechanical and tribological properties of all three composites, which was attributed to the synergistic effect of nanoparticles and PTFE:a. For mechanical properties, nanoparticles enhanced the interaction between macromolecular chains, while PTFE improved the compatibility between inorganic fillers (nanoparticles and MoS2) and POM matrix. b. For tribological properties, PTFE facilitated the formation of the transfer film while nanoparticles strengthened the interaction between transfer films and the counterpart.4. CNF/epoxy nanocomposites with various contents of CNF were prepared by solution casting. The results showed that 1 wt%CNF/epoxy nanocomposite had the highest strength as well as the modulus (both Young's modulus and storage modulus) due to the uniform distribution of CNF in matrix. The predicted values of the Young's modulus and storage modulus using a modified Halpin-Tsai equation that accounts for the effect of the CNF agglomeration compared fairly well with those obtained experimentally. The AC electrical behaviors of the CNF/epoxy nanocomposites exhibit a typical insulator-conductor transition. The conductivity increased by four orders of magnitude with the addition of 0.1 wt% (0.058 vol%) CNF, and ten orders of magnitude for nanocomposites with CNF volume fractions higher than 1 wt% (0.578 vol%). The measured values of the conductivity of the nanocomposites conformed to the percolation theory and showed a low percolation threshold at 0.057vol%.5. Nano-Al2O3/PTFE/epoxy fabric nanocomposites were made by hand lay-up process, the synergistic effect of nanoparticles and PTFE were studied. It was found that:a. The addition of nanoparticles could enhance the fiber-matrix adhesion. The improvement of fiber-matrix adhesion to some extent could enhance the tensile properties. But too strong fiber-matrix adhesion was unfavorable to the tensile properties causing the brittle fracture of the fabric composite. b. Matrix played the most important part in wear-resistant properties of the fabric nanocomposite once fillers were added. That is to say, nanoparticles enhanced the wear-resistance of epoxy resin when they were added to epoxy resin, thus the anti-wear properties of polyester fabric nanocomposite increased. However, the friction coefficients of polyester fabric nanocomposites were higher than corresponding polyester fabric composites.6. Epoxy based fabric composites containing attapulgite (ATP) and polytetrafluoroethylene (PTFE) were prepared by hand lay-up process. The results showed that the treatment of ATP resulted in the formation of the covalent link between the treated ATP nanorods and the epoxy matrix, which enhanced the tensile properties of the matrix. Also, the fiber-matrix adhesion was improved due to the high surface energy of the ATP nanorods. Thus, the tensile properties of the fabric composites increased due to the above reasons.16 wt% was the critical overall content of the fillers, exceeding which the fillers had a strong tendency to agglomerate lowering the tensile strength. ATP:PTFE= 1:1 was the optimal relative content ratio, at which ATP and PTFE acted synergisticly to further improve the tensile properties of the fabric composites.
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