Characterization And Microscopic Mechanism Of Polymer/Ceramic Interface

The interfacial properties and micro-mechanism of polymer/ceramics have attracted much attention in recent years.The strength and stability of polymer/ceramic interface significantly affect the service life and service reliability of the material and structure,so it is of great significance to study its mechanical behavior and mechanism.Based on micro-molecular dynamics simulation and macro-experiment,this paper established a numerical model of PP/SiO₂ interface composed of polypropylene（PP）and SiO₂,studied its tensile and shear behavior,analyzed the evolution law of interface performance and interface microstructure,revealed the intrinsic fracture mechanism of polymer/ceramic interface,and characterizes its interface damage law.The main results are as follows:（1）The tensile properties and microscopic mechanism of PP/SiO₂ interface are studied.A molecular dynamics model which characterizes the tensile properties of PP/SiO₂ interface was established.It is found that the relationship between interfacial stress and interfacial displacement under tensile load can be divided into strengthening stage,damage stage and complete failure stage.Its interface strength and interface fracture energy can reach 0.115 GPa and 0.068J/m²,respectively.With the increase of interfacial displacement,the typical PP chain at the interface gradually change from line contact parallel to the interface to point contact,and finally it is completely disconnected from the SiO₂ surface under the attraction of other PP chains.The interface strength（0.48 MPa）and interface fracture energy（0.834 J/m²）of PP/SiO₂ samples are further measured experimentally,and the reasons for the difference between microscopic numerical simulation and macroscopic experimental measurement results were analyzed.（2）The factors such as stretching speed and temperature on interfacial tensile properties were systematically studied.The results show that the interface strength and interface fracture energy of PP/SiO₂ interface increase with the increase of stretching speed.When the stretching speed increases from1 m/s to 1000 m/s,the interface strength increases from 0.115 GPa to 0.254 GPa,and the interface fracture energy increases from 0.059 J/m² to 0.083 J/m².This is because when the stretching speed is high,the PP chain falls off the surface of SiO₂ and it has no time to deform,which leads to the fracture of PP/SiO₂interface approximately smoothly at the interface.The interface strength and interface fracture energy of PP/SiO₂ interface decrease with the increase of temperature.When the stretching speed is 10 m/s,at room temperature,the interface strength and interface fracture energy are 0.151 GPa and 0.063 J/m²,respectively.When the temperature is higher than the glass transition temperature of PP（267 K）,the interfacial fracture behavior changes from brittle fracture to continuous fracture.（3）The shear properties of PP/SiO₂ interface and its influencing factors were studied.Under the shear load,the interfacial shearing stress changes periodically with the shearing displacement.When the shearing speed is 1000m/s,the peak shearing stress of PP/SiO₂ is 352.0 MPa.With the decrease of shearing speed,the peak shearing stress decreases.With the increase of amplitude of the interface or the decrease of wavelength of the interface,the interface of SiO₂ becomes rougher,the peak value of shearing stress increases.