Interface Modification And Mechanical Properties Of 2D-C_f Reinforced Phosphate Polymer Composites

With the two-dimensional continuous carbon fiber（C_f）as reinforcing phase,C_f reinforced phosphate polymer composites（C_f /phosphate）were prepared in this paper,which got help from the ultrasonic-assisted impregnation process and the characteristics of low-temperature curing of phosphate polymer matrix.The effects of matrix composition and fiber content on the properties o f the composites were investigated.The effects of different methods on the surface modification were studied.The interface of the fiber-matrix interface was designed and controlled by comparing the effects of different methods on the surface modification of C_f.The effects of high temperature treatment and Sol-Si O₂ re-treatment on the properties of the composites were studied finally.The results show that the addition of appropriate amount of curing agent in the matrix can significantly improve the mechanical properties of C_f /phosphate composites at room temperature.The matrix in composites was more fully impregnated with fiber when curing agent content was 20wt%,which was the optimal content of curing agent in the matrix.When the content of carbon fiber was 5 0vol.%,the toughness of C_f on the matrix is the best and the fiber/matrix ratio is appropriate,which leads to less internal defects of the system and excellent mechanical properties of the composites with flexural strength up to 125.7MPa and elastic modulus is up to 33.5GPa.And at the same time,the composite material exhibits ductile fracture characteristics and shear failure modeBy comparing the effect of different methods on the surface modification of C_f,it was found that the effect of the impregnation treatment of oxidized graphene solution and the oxygen oxidation treatment on the surface of the fiber was proved to be the best,and the effect of introducing the oxygen-containing functional groups to surface and improving the surface wettability of C_f was satisfactory,which can play a significant effect on the impregnation effect of the bundles and the improvement of the fiber-matrix interface state.However,these two modification methods failed to improve the mechanical properties of the composites effectively.The reason may be that the simple physical adsorption binding force between the graphene oxide and the fiber is small,the air oxidation treatment causes damage to the fiber itself and the excess matrix reduced fiber content.Then the C_f was subjected to acetone impregnation and desalting treatment,which help improve the fiber-matrix interface and ensure the ratio of fiber/matrix.The mechanical properties of the composites were improved further: the flexural strength and elastic modulus of the composites after pretreatment of acetone were 156.1MPa and 39.7GPa,respectively,and increased by more than 24% and 33% respectively than before.After the high temperature treatment of the composites,the shrinkage of the matrix lead to the introduction of defects in the system,resulting in the decrease of the mechanical properties.The bending strength of the composites after treatment at 900℃ was only 32% before the heat treatment,and the composite material still showed tough fracture characteristics.Acetone impregnated modified fiber was more effective for improving the mechanical properties of composites at high temp erature,and the flexural strength of composites after 900 ℃ treatment was nearly 1 times higher than that of non-impregnated fiber reinforced composites.The modification of oxidized graphene solution and the modification of air oxidized fiber have a significant improvement effect on the mechanical properties of composite materials treated at 600℃ and 900℃.The Sol-SiO₂ re-treatment was carried out on the composites after 900℃ high temperature treatment,which eliminated the internal defects in composites caused by high temperature treatment and significantly improved the mechanical properties of the composites.The flexural strength of the composites after 40wt% Sol-Si O₂ reimpregnation treatment can be improved by more than 107%.