Research On Interface Modification And Mechanical Properties Simulation Of LaPO₄@（Al₂O₃）_f/Al₂O₃ Composites

In the aerospace field,the demand for thermal structure materials is increasingly urgent.Oxide fiber reinforced oxide matrix composites have excellent oxidation resistance and mechanical properties,and have extensive application potential in aerospace thermal structure materials.In this paper,a continuous alumina fiber reinforced alumina composite modified by lanthanum phosphate（LaPO₄）interface phase was prepared with typical oxide/oxide composites as the material system.By studying the effect of process parameters on the interface phase of LaPO₄,LaPO₄interface phase was rapidly prepared on alumina fiber.It overcomes the shortcoming of time-consuming preparation of LaPO₄interface phase by hydrothermal method.The instantaneous degradation model and progressive damage degradation model with 3d Hashin criterion as failure criterion were further established to evaluate the applicability of the two models in alumina/alumina composite simulation,laying a foundation for engineering application.The specific research contents are as follows.（1）This paper studies the preparation of lanthanum phosphate quickly on the alumina fiber interface of preparation technology,through the introduction of potential difference in the process of preparing interface depends on driving force,to speed up the preparation process of the interface,the p H,concentration of precursors,sintering temperature,soaking-sintering cycles of phosphoric acid lanthanum interface thickness and uniformity,covering,the influence of surface defects,the results show that,The lanthanum phosphate interface with good interfacial quality can be prepared quickly by electrostatic adsorption method,and the interfacial thickness prepared by one impregnation-sintering cycle is about 0.5μm.（2）（Al₂O₃）_f/Al₂O₃composite was prepared by hot pressing of slurry.The effect of heat treatment temperature on the mechanical properties of F800 alumina fiber bundle and（Al₂O₃）_f/Al₂O₃composite was studied,and the mechanical parameters were obtained.Abstract:LaPO₄@（Al₂O₃）_f/Al₂O₃composite was prepared.The influence of lanthanum phosphate interface on the bending properties of（Al₂O₃）_f/Al₂O₃composite was studied.The mechanism of bending fracture of（Al₂O₃）_f/Al₂O₃composite was investigated by macro and micro structure,The results show that the introduction of LaPO₄interfacial phase can adjust the binding between fiber and matrix and promote the fiber pulling out,thus greatly increasing the toughness of the composites..（3）Based on the collected parameters,the damage evolution of（Al₂O₃）_f/Al₂O₃composite and LaPO₄@（Al₂O₃）_f/Al₂O₃composite were studied using finite element simulation method.The instantaneous degradation model and progressive damage degradation model subroutines were written based on three-dimensional Hashin criterion as failure criterion to simulate composite materials and obtain the simulated mechanical response,which was compared with the experimental results.The accuracy and applicability of the two damage models for（Al₂O₃）_f/Al₂O₃composites and LaPO₄@（Al₂O₃）_f/Al₂O₃composites were evaluated.The results show that the transient degradation model presents the failure mode of brittle fracture and can better simulate the mechanical behavior of（Al₂O₃）_f/Al₂O₃composites.The progressive damage degradation model shows ductile fracture failure mode and can well simulate the mechanical behavior of LaPO₄@（Al₂O₃）_f/Al₂O₃composites.The two models show almost the same results in the linear elastic stage of the initial stress-strain curve,and have good accuracy in strength simulation,It provides a reference for subsequent material calculation.