Super strong and tough bioglass-ceramics composites with bioinspired interdigitated suture interface and 3D helicoidally arranged fiber

Bioglass-ceramics hardly possessed satisfied strength and toughness simultaneously. The poor toughness and deformability heavily hinder their application in load-bearing bone repair. Drawn from the interdigitated sutures and laminated microstructure in nature, a bioinspired interdigitated suture interface between bioglass (BG) and hydroxyapatite (HA) and 3D helicoidal arrangement of fiber were constructed in bioglass reinforced hydroxyapetite (GHA) composites, creating super strong and tough carbon fiber reinforced GHA (CF/GHA) hybrid composites. The microstructure, reinforcing mechanism, and 3D failure mode of the composites were investigated at the microscale and nanoscale. The GHA composites sintered at 980 °C exhibited a compressive strength at 324 MPa and a failure strain at 9.9 % which was 6.89 times and 3.19 times that of HA ceramics, respectively. The significant performance improvements can be attributed to elliptical disc-like BG homogeneously distributed in the HA matrix, the interdigitated suture interface of about 1 μm thickness, and chemical bonding between BG and HA matrix. The compressive strain and the fracture toughness of spatial Bouligand structural CF/GHA with layer thickness of 250 μm and K/4 CF per layer (SB DK/4-GHA980) reached 14.0 % and 35 MPa m 1/2 , which increased by 41.4 % and 45.8 % compared with that of GHA980, respectively. The thin layer (small layer thickness) in SB DK/4-GHA980 can produce a more tortuous crack deflection path, exhibiting the higher fracture toughness. The toughening mechanism of spatial Bouligand structural CF/GHA hybrid composites included Bouligand structural CF, fiber debonding and pullout, and the step-like fracture due to the addition of CF based on the strengthening and toughening effect of BG in the composites. The composites can be used in the load-bearing bone application owing to the similar strength and superior toughness to human cortical bone and increased deformability. The study opens a new avenue to strengthen and toughen brittle ceramics.