Spatial toughening mechanism of ZrB2-SiC spiral fibers composites up to 1500 °C via SEVNB with femtosecond lasers and 3D-XRM methods

Ceramics containing profiled fiber-like additives (nanotubes, whiskers, etc.) show high mechanical properties. However, the toughening mechanism is debated due to its complex multi-scale microstructure. In this work, ZrB 2 (Z)-20 vol%SiC(S) spiral fibers (ZS sf ) were prepared by liquid rope effect and non-solvent induced phase separation, while quantitative relation of mechanical properties and structure were investigated by using SEVNB with femtosecond lasers and in-situ 3D-XRM simulation. The ZrB 2 -SiC composites with hierarchy ZS sf exhibited a ∼60 % increase in fracture toughness (5.45 MPa m 1/2 ) compared with blank composites, while the toughening efficiency of the hierarchy ZS sf increased over 2 times compared to the 1D and 2D toughening additives. The ZS sf with a thin graphite-like layer and spiral structure with hierarchy pores provided a torsional release effect that changed brittle fracture to the pseudoplastic fracture, where topological interlocking of 3D crimped structure hindered rapid cracking propagation. Additionally, the enhanced toughness was attributed to the uniform reconstruction of the stress field induced by hierarchical inner pores. The preserved 3D topological interlocking and uniform stress reconstruction lead to the highly stable fracture toughness of the ZS sf composites up to 1500 °C.