| Fiber metal laminate is composed of alternating thin metal sheet and fiber reinforced composite layer.It combines the excellent properties of fiber composite and metal material.Fiber metal laminate can greatly improve the strength,fatigue resistance,impact toughness,corrosion resistance.It has high crack resistance and good damage tolerance of a single material.It is an important material in the field of aerospace and shipbuilding.In addition,with the rapid development of the aerospace field and the increasing requirements of the China's independent research and development(R&D)technology level,the research on the design and development technology,preparation technology and production equipment technology of fiber metal laminates has attracted much attention However,due to the difference of physical properties between the two materials,it is difficult to coordinate the forming of fiber-reinforced metal laminates under the combined energy field of heat and force,resulting in interface delamination,fracture and other problems.There are many scientific problems to be revealed in interface interaction,bonding theory and mechanical properties.In this paper,aluminum alloy(AA6061)is used as the outer metal layer and carbon fibre reinforced plastics(CFRP)is used as the inner reinforcement.The physicochemical control mechanism of Al/CFRP/Al laminate was studied by the physical and chemical double surface control of aluminum alloy sheet and the preparation of flexible interface layer.The influence mechanism of interface microstructure and component thickness ratio on the properties of the laminate was analyzed.Based on mechanical properties experiments,the effects of macro and micro structures of flexible interface layer on interface properties of fiber metal laminates under different manufacturing processes were studied and the toughening mechanism of flexible interface of Al/CFRTP/Al composite laminates was revealed,which provided theoretical basis and guidance for the further and wide application of carbon fiber metal laminates lightweight.Al/CFRP/Al laminates were prepared through autoclave by changing the surface roughness of aluminum alloy AA6061 and carbon fiber reinforced unidirectional prepregs.The effect of surface state of aluminum alloy on the microstructure of composite interface and the bonding strength of composite plate was studied and the bonding mechanism was analyzed.The results show that the interfacial shear strength of Al/CFRP/Al laminates first increases and then decreases with the increase of sandpaper particle size.Under the action of hot pressing,the bonding mechanism of resin and aluminum alloy is mechanical anchoring and physical adsorption.The bonding mode of mechanical anchorage alone will make the laminates form weak interfacial bonding strength and reduce the use value of Al/CFRP/Al laminates.Therefore,the Al/CFRP/Al laminate was prepared by surface pretreatment of anodizing.The intermolecular force between epoxy resin and metal was excited by porous nanostructured oxide film.The chemical bonding between different physical materials was realized.The effects of anodizing time and voltage on the microstructure and mechanical properties of Al/CFRP/Al laminates were studied by changing anodizing process parameters.The results show that the interfacial shear strength of Al/CFRP/Al laminates reaches the maximum value when the anodized voltage and time are 25 V and 20 min respectively.The interfacial shear strength is 34.9% higher than that after acid and alkali washing.This is due to the formation of porous nanostructures on aluminum alloy surface after anodizing,which not only increases the wetting effect of AA6061 and CFRP,but also promotes the formation of Al-O-C chemical bond between epoxy resin and AA6061 due to the large amount of hydroxyl groups in the oxide film.Thus,the bonding strength of Al/CFRP/Al laminates is greatly improved.Based on the research of anodizing pretreatment,the surface modification of anodized aluminum alloy with different kinds of silane coupling agents was carried out by introducing“flexible” interface layer(through the addition of special media,the affinity reaction can occur with two different materials,and the small coordinated slip can occur during deformation).The effects of different concent and types of silane coupling agents on the microstructure and mechanical properties of Al/CFRP/Al laminates were studied.The results show that the addition of the two silane coupling agents forms a flexible layer at the interface,which increases the wettability between the resin and the aluminum sheet and eliminates the thermal stress,so that the Al/CFRP/Al laminate achieves a higher bonding strength.Compared with silane coupling agent A-187,the interfacial bonding strength and bending strength of the Al/CFRP/Al laminate with silane coupling agent A-1387 have been greatly improved.This is because silane coupling agent A-1387 has more interaction points with the main network structure of epoxy resin.Not only the amino group at the end of the molecular chain can be chemically bonded with the resin,but also the secondary amine group(-NH-)in the molecular chain can be chemically bonded.Therefore,the cohesive strength and modulus of the interface layer are relatively high and the mechanical properties of the laminate are greatly improved. |
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