Construction Of Polyphosphazene/Carbon Fiber Multi-scale Reinforcement And Its Composites Interfacial Properties

The lightweight materials have caused extensive concern due to environmental degradation and energy crisis.Carbon fiber(CF)reinforced polymer composites are one of the ideal alternatives because of their excellent properties including light weight,high strength and high modulus.However,CF commonly has smooth and chemical inert surface,which lead to weak interfacial bonding between the fiber surfaces and polymer matrix.The strength,toughness and chemical stability of composites are largely affected by the interface between fiber and resin matrix.Therefore,it is very important to develop a facile and efficient approach for improving the interfacial properties of CF composites without damaging the strength of the fiber,so as to promote the development and application in the new generation of automobiles,aerospace,marine science and other military and civil fields.In this thesis,we prepared poly(cyclotriphosphazene-co-4,4?-sulfonyldiphonel)(PZS)microspheres,nanotube/CF multi-scale hybrid reinforcement to improve the interfacial adhesion of CF composites.The effects of surface modification on the surface and interface properties of CF and the resulting composites were investigated systematically.The main research is as follows:(1)The multi-scale PZS microspheres/CF hybrid reinforcement was prepared by a facile in situ polymerization based on the interphase microstructure tailor of CF/epoxy composites.The test results indicated that the interfacial adhension of CF/ epoxy composites was significantly improved for the introduction of PZS microsphere and coating which improved the wettability,chemical reactivity and mechanical locking effect between CF and matrix resin.After modification,the interfacial shear strength(IFSS)of fiber reinforced epoxy composites increased obviously from 68.91 to 84.75 MPa with an increase of 23.0%.Moreover,the tensile strength of modified fiber also increased by 15.59% because of the PZS coating can heal the surface defects to some extent.(2)We proposed a facile and effective method for assembling PZS nanotube onto CF as a novel multi-scale hybrid reinforcement through in situ template polymerization using hexachlorocyclotriphosphazene(HCCP)and bis(4-hydroxyphenyl)sulfone(BPS)as monomers.After modification,the IFSS of fiber reinforced epoxy composites showed an increase of 26.41%.The improvements on interfacial properties can mainly be attributed to mechanical interlocking effect,wettability and chemical reactivity caused by PZS nanotube coating.Furthermore,the tensile strength of modified fiber also increased from 4.17 GPa to 4.85 GPa by repairing the surface defects and the synergistic enhancement of the hybrid PZS nanotube coating.In addition,the polydopamine modified layer was deposited on the surface of PZS nanotube/CF by the oxidation of dopamine,which further enhanced the IFSS to 90.32 MPa.(3)The effect of submicron PZS microspheres and PZS nanotube layer on the IFSS of CF reinforced thermoplastic polyamide(PA6)composites was investigated.After modification,the surface roughness,wettability of fibers could be significantly increased for introducing PZS microspheres or PZS nanotubes.Moreover,the transition layer was formed at the interface between fiber and resin.So the IFSS of CF/PA6 composites increased to 53.79 MPa and 52.32 MPa,showed increases of 42.75% and 38.85%,respectively.Therefore,the structure and nature of PZS coating have better effect on the interfacial adhesion of thermoplastic composites.The design and preparation of PZS/CF multi-scale reinforcement and the interfacial properties of resin composites were studied in this research work.It is helpful to solve the common problem of low interfacial adhesion of CF reinforced thermosetting and thermoplastic composites,and it provides a new method for the construction of the hierarchical structures and improving the interfacial properties of advanced fiber reinforced composites.