| Ceramic-metal and ceramic-polymer composite structures are widely used in many engineering fields because of their good mechanical properties.But most of the traditional composite structures are laminated composite structures with simple structure and single function,which can not meet the development needs of functional integration of new composite structures.The functional gradient structure based on the bionic structure concept such as shell has further promoted the development of new composite structures.However,the high-precision complex profiled gradient structure can not be obtained by traditional fabrication techniques.The appearance of photocuring additive manufacturing technology provides ideas for the development of complex ceramics and their composite structures.Photocuring additive manufacturing technology has the advantages of no mold,fast forming speed,high precision,and short manufacturing cycle,which greatly promotes the application and development potential of complex special-shaped ceramic structures.In this paper,the gradient Al2O3 ceramic lattice was first prepared by the photocuring and adding manufacturing technology,and then Al Si10Mg and polyurea were filled in the pores of the lattice structure by the vacuum melt infiltration technology and the high-temperature infiltration technology,respectively.Finally,the gradient composite structure（FGCM,FGCP）with good mechanical properties was obtained.The effects of different gradient rates on the mechanical properties and failure modes of gradient Al2O3 ceramic lattice and its composite structures under quasi-static compression and dynamic impact loads are discussed.Firstly,the 3D printing process of Al2O3 ceramic gradient lattice and its static and dynamic mechanical properties were studied in this paper.Based on an octahedral truss lattice structure,Al2O3 ceramic gradient lattice with gradient characteristics is designed in this paper.By controlling the relationship between cell pillar and density,the interlayer gradient rate is 0%,10%,20%,and 30%,respectively.Al2O3 ceramic gradient lattice was prepared by digital light processing and light curing 3D printing（DLP-3D）.The light intensity of the DLP-3D printing process is controlled as12000μW/cm3,the exposure time of the first layer and other layers is set as 7s and 4s,and the thickness of the paste is controlled as 275μm～300μm.The printed Al2O3 ceramic gradient lattice body was discharged and sintered at 800℃and 1600℃,and the final Al2O3 ceramic gradient lattice with complete structure and dense material was obtained.Next,the mechanical properties and failure modes of Al2O3 ceramic gradient lattice under quasi-static and dynamic conditions are systematically studied.Therefore,with the increase of gradient rate,the mechanical properties of the Al2O3 ceramic gradient lattice decrease as the resistance of the bottom cell to load decreases.When the gradient rate reaches 30%,the quasi-static mechanical properties（compressive strength,Young’s modulus,and energy absorption）reach 6.7MPa,0.66GPa,and 0.0338MJ/m3,and the dynamic impact mechanical properties（impact strength and energy absorption）reach 41.06MPa and 0.65MJ/m3,respectively.Secondly,the ceramic/metal multiphase composite structure（FGCM）based on an Al2O3 gradient lattice was studied.In this study,aluminum alloy Al Si10Mg was melt-permeated into the pores of the Al2O3 gradient lattice at 950℃and the graded ceramic/metal composite structure（FGCM）was obtained.The FGCM samples obtained showed good integrity,good bonding between ceramic phase and metal,and no obvious interfacial defects.The mechanical properties and failure modes of FGCM under quasi-static and dynamic conditions were systematically studied.It was found that the quasi-static and dynamic mechanical properties of FGCM were enhanced with the increase of gradient rate.Moreover,the mechanical properties of FGCM increased gradually compared with the Al2O3 gradient lattice.When the gradient rate reached 30%,FGCM showed the best performance improvement,and its quasi-static mechanical properties（compressive strength,Young’s modulus,and energy absorption）were176.1MPa,4.56GPa and 4.63MJ/m3,which were 2528.4%,590.9%and13598.2%higher than Al2O3 gradient matrix,respectively.The dynamic mechanical properties（impact strength and energy absorption）are239.18MPa and 11.10MJ/m3,which are 482.5%and 1607.7%higher than the Al2O3 gradient lattice,respectively.Finally,the study of ceramic/polyurea polyphase composite structure（FGCP）based on an Al2O3 gradient lattice was continued.Gradient ceramic/polyurea composite structures（FGCP）were obtained by leaching polyurea into the pores of the Al2O3 gradient lattice at 80℃.The obtained FGCP samples were structurally intact without obvious defects.The mechanical properties and failure modes of FGCP under quasi-static and dynamic conditions were systematically studied.The mechanical properties of FGCP were enhanced with the increase of gradient rate due to the similar effects of polyurea and metal in composite structures.When the gradient rate was 30%,FGCP showed the greatest performance improvement compared with the Al2O3 gradient lattice.The quasi-static mechanical properties（compressive strength and energy absorption）are17.48MPa and 0.54MJ/m3,which are 160.9%and 1468.0%higher than that of the Al2O3 gradient matrix,respectively.The dynamic mechanical properties（impact strength and energy absorption）are 110.79MPa and2.44MJ/m3,which are 169.8%and 275.4%higher than the Al2O3 gradient lattice,respectively.With the addition of Al Si10Mg/polyurea,the brittle fracture of the Al2O3 gradient lattice transforms into ductile deformation,and its mechanical properties are greatly enhanced.With the increase of the gradient rate of ceramic structures,the performance of the composite structures to withstand and resist the impact is gradually enhanced,which provides ideas for the application and development of impact-resistant composite materials and structures. |
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