Study On The Interface Enhancement And Performance Of Carbon Fiber/nylon 6 Composites "bio-glue-nanoparticles

Carbon fiber reinforced polymer（CFRP）composites have excellent properties such as high strength,low weight and high temperature resistance,and are widely used in many industrial fields such as automotive,defense,and sports.Due to shorter cycle times and higher reusability than thermoset composites,thermoplastic resins have attracted more attention in the past few years.Due to its low cost,versatile machinability and good mechanical properties.As a commonly used engineering plastic,polyamide 6（PA6）has attracted more and more attention because of its high tensile properties,good heat resistance and good processing properties,and is considered to be the main matrix of CFRP,while short fiber（SCFs）reinforced thermoplastic composites are welcomed by academia because of their advantages such as continuous processing,recycling,outstanding thermal and mechanical properties.However,due to the smooth surface and chemical inertness of CFs,the interfacial adhesion of the composites is weak,which affects the comprehensive properties of CFRP composites.In this paper,the surface element composition,microscopic morphology and wettability of CFs were studied.The effects of processing properties,thermal/mechanical properties and interface layers on the crystallization behavior of composites,and the interface and matrix strengthening mechanisms of composites were deeply analyzed.The main research contents and results are as follows:1.The polydopamine/nano silica（PDA-SiO₂）interface layer was constructed on the surface of carbon fiber by gradually grafting polydopamine and nano-SiO₂,and then blended with polyamide 6 to prepare carbon fiber reinforced polyamide 6 composites（CFs/PA6）.The effects of PDA-SiO₂ interface layer on the crystalline structure and behavior,thermal properties and mechanical properties of CFs/PA6 composites were investigated.In addition,the interface reinforcement mechanism of composite materials is analyzed in depth.This interfacial layer significantly increases the number of CF surfactant groups and their wettability.The tensile strength of CF-PDA-SiO₂/PA6 composites was increased by 28.09%,19.37%and 26.22%compared with untreated CF/PA6,CF-PDA/PA6 and CF-SiO₂/PA6 composites,respectively,due to the hydrogen bonding of hydroxyl groups on nano-SiO₂ and amide groups on PA6 molecular chains and the mechanical meshing between the two,resulting in increased interfacial bonding between CFs and PA6 substrates.The thermal stability,crystallization temperature,crystallinity and glass transition temperature（T_g）of CF-PDA-SiO₂/PA6 composites were improved,which was attributed to the heterogeneous nucleation of nano-SiO₂ in the crystalline region and the hydrogen bonding of PA6 molecular chains in the amorphous region.In addition,the interface reinforcement mechanism of composite materials is also elucidated.2.The "TA-KH550-ZnO" grafted interface layer was constructed on the surface of carbon fiber to prepare carbon fiber reinforced polyamide 6 composites（CFs/PA6）by using an environmentally friendly and effective method.The effects of"TA-KH550-Zn O"grafted interface layer on the crystalline structure and behavior,thermal properties and mechanical properties of CFs/PA6 composites were investigated.The tensile strength of CF-TA-KH550-Zn O/PA6 composites was increased by 41.69%,35.20%and 26.42%compared with untreated CF/PA6,CF-TA-KH550/PA6 and CF-Zn O/PA6 composites,respectively.The thermal properties of CF-TA-KH550-Zn O/PA6 composites are also significantly improved,which is caused by the heterogeneous nucleation of Zn O and hydrogen bonds with PA6 molecular chains.On this basis,the interface reinforcement mechanism of the composite is also explained.3.On the basis of the fiber modification method of the previous experiment,the method of melt blending was used to add PK to modify the PA6 matrix.The test results show that the thermal and mechanical properties of the composite materials are improved to a certain extent compared with the CF-TA-KH550-Zn O/PA6 composite samples of the previous system,especially the impact strength,which is increased by 37.48%（10 wt%PK）under different proportions of PK addition.37.78%（20 wt%PK）;43.71%（30 wt%PK）and 6.67%（40 wt%PK）.In addition,the interface enhancement mechanism was analyzed in depth by observing the fracture morphology of the impact test.