Dual composite architectonics: Fracture toughness and self-healing of ZrB2-SiC-TaB2 based UHTC

This study explores the effect of structural architecture of ZrB2-SiC-TaB2 composites on their fracture toughness and ability to self-heal operational surface defects. It is shown that the dual composite architecture provides a synergistic combination of several effects enhancing the fracture toughness of the material: crack arrest in the developed system of polymodal interphase boundaries, and formation of elastic microstress fields. In addition, SiC that is rapidly oxidized and forms an easily fusible borosilicate layer endows MeBx-based dual composites with the ability to self-heal surface defects when operating at temperatures above 1000 degrees C in an oxygen -containing environment, preventing crack initiation from surface stress concentrators. The analysis of the re-sidual strength after self-healing in comparison with the initial data of the studied materials allowed the optimal matrix-inclusion ratio, minimizing the loss of reliability.