| In this dissertation,polyethylenimine and titanium dioxide were used to modify halloysite nanoparticles.The modified halloysite nanoparticles were added to carbon fiber/epoxy composites to investigate the effects of the modified halloysite nanoparticles on the mechanical properties,cryogenic cycling properties and ultraviolet radiation properties of carbon fiber/epoxy resin properties.The main content is as follows:?1?Polyethylenimine was coated on the surface of halloysite nanoparticles by chemical grafting,and the polyethylenimine/halloysite?PEI/HNT?nanoparticles with different polyethylenimine loads were prepared by adjusting the mass ratio between polyethylenimine and halloysite.Carbon fiber/epoxy?CF/EP?composites adding PEI/HNT were fabricated via hot pressing method.The results show that polyethylenimine can form a coating on the surface of halloysite,and the surface of PEI/HNT nanoparticles is rich in–NH2groups.Compared with CF/EP composites without nanoparticles,when 1 wt%PEI/HNT-2?polyethylenimine to halloysite mass ratio of 1:2?nanoparticles were added to carbon fiber/epoxy composites,nanoparticles had the best enhancement effect on composites,and the flexural strength and flexural modulus of composites increased by 17%and 21%respectively.This is due to the fact that polyethylenimine improves the dispersion of the nanoparticles in the epoxy and enhances the interface between the nanoparticles and the epoxy.Cryogenic cycle experiments?-196??25??were conducted on CF/EP-PEI/HNT-2-1wt%,the results shownd that the flexural properties of the composites were good after 30 cryogenic cycles,and the flexural strength and flexural modulus retention rates were 96%and92%,respectively.This is because the addition of PEI/HNT-2 nanoparticles effectively reduces the thermal expansion coefficient of the composites.UV irradiation experiment on CF/EP-PEI/HNT-2-1wt%composite material,the experimental results show that the composites maintain good flexural properties after 300 hours of UV irradiation.However,due to the limited ability of HNT to shield ultraviolet rays,the flexural properties of the composite decreased when the irradiation time reached 500 h.?2?Titanium dioxide was loaded on the surface of halloysite via sol-gel method and then polyethyleneimine was grafted on the halloysite loaded with Ti O2 to prepare polyethylenimine modified titanium dioxide-halloysite nanoparticles?PEI/Ti O2-HNT?.Using PEI/Ti O2-HNT nanoparticles as additives,the PEI/Ti O2-HNT nanoparticles reinforced carbon fiber/epoxy resin composites were prepared by hot pressing process.The experimental results show that the titanium dioxide load on the surface of Ti O2-HNT nanoparticles prepared by sol-gel method is uniform.PEI/Ti O2-HNT nanoparticles are rich in-NH2 groups.In PEI/Ti O2-HNT nanoparticles enhanced carbon fiber/epoxy resin composite material mechanics property tests show that when adding1 wt%of PEI/Ti O2-HNT-1 nanoparticles,composite material has the best flexural property,relative to not add nanoparticles of CF/EP composites,flexural strength and flexural modulus increased by 16.8%and 15.03%respectively.This is due to the fact that polyethylenimine improves the dispersion of the additive in the epoxy resin and enhances the interface between the additive and the epoxy resin.Best for mechanical property enhancement effect of CF/EP-PEI/Ti O2-HNT-1-1wt%for low temperature cycle experiment found that into 30 times after low temperature cycle composite flexural property is good,the flexural strength and flexural modulus of keeping rates were 95%and 96%respectively,this is due to the PEI/Ti O2-HNT-1 between nanoparticles and epoxy resin has good interface bonding,after multiple temperature cycle interface bonding remained stable.UV irradiation experiments on CF/EP-PEI/Ti O2-HNT-1-1wt%showed that the flexural property of the composites remained good after 500 h of UV irradiation,which was caused by the increased UV shielding property of halloysite nanoparticles under the load of Ti O2. |
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