Size Effect Of Ceramic-Metal Functionally Graded Composites Under Impact Load

The metal-ceramic functionally graded materials(FGM)is a composite of a ceramic-to-metal functionally graded layer that combines the superior properties of ceramics and metals due to its gradient layered structure.The ceramic-rich side provides good protection against impact,while the metal-rich side provides toughness to maintain structural integrity for as long as possible.The metal-ceramic functionally graded materials and functionally graded sandwich reinforcements are widely used in the aerospace,nuclear,and mechanical industries due to their excellent impact resistance and high strength and stiffness.The engineering structure encounters impact loads during manufacturing,use and maintenance.The elastoplastic deformation and damage of conventional metals and metal alloys can be found by visual inspection of the surface.However,FGM exhibits limited plastic deformation,and visual inspection is not allowed due to the conversion of impact energy into a form of damage such as delamination,matrix cracking or fiber breakage.Therefore,its impact response analysis is very important for the design of advanced impact structures in the aerospace,nuclear and mechanical industries.In this paper,we discuss the strength prediction model of functionally graded materials,and use the developed models to analyze elasto-plastic deformation of metal-ceramic functionally graded plates under low-velocity impact.The numerical simulation and analysis of the drop-weight impact test were carried out.The dislocation-based continuum model explicitly accounts for strengthening effects due to geometrically necessary dislocations and plastic strain gradient in impact analysis of metal-ceramic functionally graded plates by combining Taylor dislocation model and Tamura-Tomota-Ozowa(TTO)model.Further,an enhanced continuum model explicitly accounts for the strengthening associated with strain rate in impact analysis of metal-ceramic functionally graded plates by combining Johnson-Cook model.we describe the effective linear elastic properties of the metal-ceramic functionally graded plates based on the Mori-Tanaka scheme.The elastic-plastic impact responses of SiC/Al functionally graded plates with the micron-scale particle sizes and compositional gradient exponents are studied under varied impact velocities.The numerical simulation experiment uses the finite element method,and we compare the numerical simulation results with the conventional model results and the experimental data reported in references.Conventional model tend to predict the diameters of after-impact impressions that have large differences with the practical situation,while the present study by using the proposed model shows that the discrepancy is mainly because the strengthening effect of the SiC particle size and strain rate is not accounted for in prior models.