Experimental Investigation And Molecular Dynamic Simulation Of Interficialadhesion Between Inorganic Fiber-epoxy Resin In Salt Solution

The chloride ions in the sea water and sea sand in concrete could lead to the corrosion of steel bars.FRP（Fiber Reinforced Polymer）is always used in seawater and sea sand concrete because of its excellent corrosion-resistance.In this paper,the interfacial bonding properties of basalt fiber（glass fiber）and epoxy resin matrix,as well as the effects of corrosion solutions on the interfacial bonding properties,were systematically investigated by experiments and molecular simulations.The main conclusions are as follows:（1）The interfacial bond properties of basalt fiber bundles-epoxy resin and glass fiber bundles-epoxy resin in corrosive solution were investigated by the self-designed basalt（glass）fiber bundle-epoxy resin micro-debonding test.The digital image correlation technology（DIC）was used to monitor the stress and strain at the adhesive end of epoxy resin during the debonding process of fiber bundle-epoxy resin.The tensile strength of basalt fiber bundle and glass fiber bundle was 165 MPa and 65MPa,respectively.The bonding strength of basalt fiber to epoxy resin was 45 MPa,which is 18%lower than that of glass fiber bundle to epoxy resin.After 28 days of corrosion,the corrosion resistance of the interface between glass fiber bundle and epoxy resin was higher than that of basalt fiber.（2）The interface models of basalt fiber/epoxy resin（aluminum-doped silica,Si（Al）O₂/epoxy resin,DGEBA+MPD）and glass fiber/epoxy resin（pure silica,Si O₂/epoxy resin,DGEBA+MPD）were established,respectively.The following works have been studied based on the molecular dynamics simulation,which contain the interaction energy of the two interfaces,the structure of epoxy resin at the interface,the interaction forms between epoxy resin atoms and substrate atoms,and the movement of ions in the multi-environment.In the dry condition,the interaction energy of aluminum-doped silica/epoxy resin is 28.42%of that of pure silica/epoxy resin.And in the solution environment,the interaction energy of aluminum-doped silica/epoxy resin was lower than that of pure silica/epoxy resin.（3）The epoxy and fiber substrate are bonded in the manner of H-bonds formed by oxygen of epoxy（Oe）and hydrogen of substrate（Hs）.The main form of ions damage to the interface are interactions between hydrogen of water（Hw）and oxygen of epoxy（Oe）,oxygen of epoxy（Ow）and hydrogen of substrate（Hs）,Na⁺and oxygen of epoxy（Oe）,Cl^-and hydrogen of substrate（Hs）,SO₄^2-and hydrogen of substrate（Hs）.And the solution ions destroy the bonding capacity by interacting with the atoms of interfacial atomic pairs（Oe-Hs,He-Os）and occupying the reactive sites of interfacial atomic pairs.（4）The microstructure and tensile strength of basalt（glass）fiber epoxy resin composite sheet in etching solution were studied respectively.The results show that the tensile strength of basalt fiber epoxy resin composite and glass fiber epoxy resin composite decreased obviously after corrosion in solution for 28 days,respectively.The influence of corrosion solution on the deterioration of mechanical properties of two kinds of sheets is as follows:simulated pore solution of sea water and sand concrete（SWSSC）>simulated pore solution of normal concrete（NC）>Na Cl solution>aqueous solution;（5）A preloading immersion aging test device was proposed to study the mechanical properties of basalt fiber epoxy resin composite sheet under the coupling effect of load and corrosion solution;Ultra-depth microscope was used to observe the surface morphology of basalt fiber resin composite sheet in-situ,under the condition of preloading and soaking real-timely.The tensile properties of basalt fiber epoxy resin composite sheets were tested by preloading and corrosion for 28 days,and the surface strain was monitored by using digital image correlation technology during the drawing process.It was found that the preloading and corrosion accelerated the decrease rate of tensile stress of sheet,compared with that of single corrosion condition.The epoxy resin cracks at the cross section,and the fiber bundles at the cross section were pulled out from the epoxy matrix with the increase of corrosion degree.