Study On Mesoscopic Failure Of Resin Mineral Composite And Its Matching With Self-healing Microcapsules

Resin-mineral composite is a new manufacturing material for machine tool base parts,and its cracking problem during service is of great concern.This material has its own essential defects such as microcracks and voids in the manufacturing process,which affects its performance,and if the microdefects in the structure are not repaired in time,the microdefects will expand and gather and spread in the form of macroscopic cracks,leading to structural damage and failure,which seriously affects the service life of machine tool base parts.Microcapsule self-healing method is one of the many self-healing technologies,the preparation process is simple and cost-effective,and its application in the resin-mineral composite machine tool foundation can sense and quickly repair the damage in the structure in time,effectively prevent the failure of the mechanical structure damage,and help improve the durability and stability of the resin-mineral composite machine tool foundation.However,the internal stresses of machine tool foundation components are complex,and the application of microcapsule self-healing technology to resin mineral composite machine tool foundations has not been st udied systematically to match the mechanical properties between the microcapsules and resin mineral composite.Based on this background,this paper conducts a discrete element simulation of the damage evolution process of resin-mineral composites for machine tool base parts to study the sprouting,expansion and penetration mechanism of microcracks inside the matrix material and the crack evolution process of resin-mineral composites from mesoscale viewpoint.The mechanical properties of microcapsule walls,the rupture behavior of microcapsules and their influencing factors a re systematically investigated,mainly including the following four aspects:(1)Meso-scale characterization of resin-mineral composites and prediction of the equivalent elastic constants of microcapsules.Based on the numerical simulation technique of discrete element of particle flow,the mesoscale characterization method of different graded aggregate particles and fiber reinforcement is proposed for the fine view characterization of resin-mineral composites,which provides the basis for the subsequent study.Since the microcapsules are composed of two parts,wall and core,changes in mechanical parameters of both materials affect the overall mechanical properties of the microcapsules.Therefore,the equivalent parameters of microcapsules were predicted,and the equivalent elastic constants of resin-mineral composites containing microcapsules were predicted by using microcapsules as inclusions in resin-mineral composites.Data are provided to support the analysis of the crack resistance of microcapsules and the rupture behavior of microcapsules in resin mineral composites.(2)Mesoscopic study on damage mechanism of resin mineral composites.Based on the particle discrete element calculation method,the three-phase discrete element model of resin-mineral composites is established by setting the contact parameter simulation interface between the aggregate particles and fibers,taking into account the load-bearing situation of the machine base parts and the discontinuous properties of the material.By realizing the loading of the structure based on the servo control mechanism,the whole process of deformation,damage,crack sprouting and destabilization damage of the composite material is numerically simulated and analyzed in detail.It is determined that the interface transition zone formed by the aggregate and the resin matrix starts cracking first,and the crack extension evolution process of the resin-mineral composite is divided into four stages according to the damage evolution curve,i.e.,crack sprouting,steady-state extension,destabilization extension and damage stage.The reinforcement mechanism of fibers and the crack evolution process are also explained fro m the mesoscale of force chain and displacement field.The results of the stu dy provide the theoretical basis for t he effective application of resin-mineral composites in machine tool base parts.(3)Analysis of the crack resistance of microcapsules in re sin-mineral composite machine tool base parts.The purpose of the crack resis tance study is to ensure that the microcapsules cannot crack prematurely and the repair agent cannot flow out prematurely without damage inside the machine tool base part.The mic rocapsules’ own physical parameters will perturb the stresses on the capsule wall under the machine tool working load.Therefore,it is necessary to study the influence of microcapsules’ own parameters such as elastic modulus of capsule wall,particle size of microcapsules,core-shell ratio(core radius/capsule wall thickness),etc.on the stresses on capsule wall,to propose conditions to meet the crack resistance of microcapsules,and to put forward design requirements for microcapsules’ parameters according to the actual situation of resin-mineral composite base parts.(4)Study of the rupture behavior of microcapsules in re sin-mineral composite machine tool base parts.The purpose of the microcapsule rupture behavior study is to analyze whether the crack will penetrate the microcapsule when it is close to the microcapsule,and to ensure that the microcapsule can rupture in t ime to repair the crack when the crack extends to the vicinity of the microcapsule.Therefore,based on the extended finite element and cohesion model,the crack expansion and connectivity process is analyzed.And on the premise of satisfying the crack res istance condition of microcapsules,the factors affecting the crack expansion path are systematically analyzed and studied from the capsule wall elastic modulus and core-shell ratio,and then the parameter requirements that microcapsules can meet the self-healing condition of resin-mineral composite machine tool base parts are proposed.