Discrete Modelling Of The Mechanical Properties Of Nacre-like Ceramics

Ceramics have been widely used in various industries due to their high strength and hardness,chemical and thermal stability and so on.Nevertheless,as a typical type of brittle materials,ceramics might facture under very small strain condition.Thus,the toughening of ceramic materials has attracted lots of attention from researchers working in material science.Natural nacre is a kind of biological material.Its unique "brickmortar" stacking microstructure renders it high fracture strength and toughness.Inspired by this unique phenomenon,researchers have successfully developed ceramics with nacre-like microstructure to increase their toughness while maintaining their fracture strength.Nevertheless,the underlying toughening mechanisms of nacre-like microstructure,i.e.,how it influences the formation and propagation of crack,is still elusive.In this work,the mechanical performance of nacre-like ceramics has been investigated by performing Discrete Element Method(DEM)simulations so as to uncover the toughening mechanism of nacre-like microstructure from the micro crystal grain scale.The possible influences of the mechanical and geometrical matching between the brick phase and mortar phase on the mechanical response of nacre-like ceramics were simulated.The main studying contents of this work are as follows.(1)The adopted DEM force models and also the generation procedure of the nacrelike numerical samples are introduced.The calculation details of some parameters including Von Mises stress,particle displacement and the length variation of solid bond are also presented.(2)The influence of mechanical matching between the component brick and mortar phases on the mechanical properties of the composites is investigated.It is found that,under the condition of same bond strengths,the lower Young’s modulus induces the higher deformation of mortar phase,which alleviates the stress concentration at the tip of crack and subsequently increases the fracture strength and toughness of the composite.When the mortar phase has the same Young’s modulus as that of brick phase but higher bond strength,micro cracks and crack deflections can appear inside the tensile-loaded composite,which subsequently leads to the increase of the toughness of the composite.(3)The influence of geometrical matching between the component brick and mortar phases on the mechanical properties of the composites is investigated.The simulation results indicate that,on the premise that the bond strength of mortar phase is significantly smaller than that of brick phase and micro crack and crack deflection appear inside the tensile-loaded composite,the interlacing of brick phase helps to increase the tensile fracture strength of the composite.Decreasing the thickness of mortar phase is in favor of the uniform distribution of stress inside the brick phase,and thus the increase of the tensile fracture strength of the composite.When the mortar and brick phases have same mechanical properties and the fractur strength of the bond inbetween mortar and brick phases is notably smaller than those of mortar and brick phases,bond breakage mainly occurs at the interface.The failure of bond at the interface leads to the formation of micro crack and crack deflection,thereby the increase of the fracture strength and toughness of the composite.