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The present study is to fabricate dense tricalcium phosphate (TCP) compacts by our newly developed underwater-shock consolidation technique and to investigate the characteristics of the compacts. By adding Al₂O₃ powder to β-TCP powder, the biocomposites were fabricated to improve the fracture toughness. Sound compacts of α- and β-TCP powders and β-TCP/Al₂O₃ biocomposite powder were fabricated without any cracks and tears. The relative densities of α- and β-TCP compacts were about 85% in as-compacted state and more 94% after annealing at 1373K for 7.2ks. Compressive strengths of α- and β-TCP compacts are 160 and 140MPa after annealing at 1373K for 7.2ks, respectively. Compressive strength and fracture toughness of β-TCP/Al₂O₃ biocomposites after annealed at 1373K for 7.2ks were 188MPa and 2.54MPa·m^1/2, which are comparable to values of human bone, respectively.

Natural nacreous composites such as nacre, teeth and bone have long been extolled for their higher strength and toughness. Understanding the toughening and strengthening mechanisms as well as the condition triggering their occurrence would be of great value to the biomimetic synthesis. In this paper, our attention is mainly focused on crack deflection and flaw tolerance, which were reported as crucial toughening and strengthening mechanisms in nacreous biological materials, respectively. By applying the "brick-and-mortar" (B-and-M) structure model, our finite element-based simulation showed that the propagating direction of a crack ending at the brick/mortar interface could be controlled by tuning the fracture strength of brick. Subsequent examination on the tensile strength (TS) of the cracked B-and-M structure indicated that in nacreous composite flaw tolerance can be achieved below a length scale determined by the ductility of mortar phase. These findings would serve as guidelines in the design and synthesis of novel biomimetic materials aiming at higher strength and toughness.

This study investigated the influence of temperature variations on the mechanical and dynamic behaviors of biobased composites incorporating a passive control layer. These composites, which include an external layer made up of Flax/polylactic acid (PLA) and an internal layer of rubber, were manufactured using 3D printing technique. To better understand their mechanical characteristics, bending tests were carried out on samples of Flax/PLA with and without a rubber coating at temperatures ranging from $20^{\circ }$C to $50^{\circ }$C. To evaluate the bending response of the materials under several temperatures settings, three-point bending tests were also conducted on the materials with different viscoelastic layer thicknesses. Additionally, resonance vibration studies were carried out at various temperatures to explore dynamic characteristics like frequencies and damping factors. The analysis of the data revealed the consequences of incorporating a functional rubber layer under diverse circumstances. The results demonstrated that increasing temperatures negatively impacts the mechanical and dynamic characteristics degradation of the composite with the viscoelastic layer. The main objective of this work is that under various thermal settings, passive control layers in biocomposites can display modified mechanical and dynamic behaviors. This understanding of how these biobased composites perform in different environments offers significant context for their possible applications.

Tissue engineering utilizes the expertise in the fields of materials science, biology, chemistry, transplantation medicine, and engineering to design materials that can temporarily serve in a structural and/or functional capacity during regeneration of a defect. Hydroxyapatite (HAp) scaffolds are among the most extensively studied materials for this application. However, HAps have been reported to be too weak to treat such defects and, therefore, have been limited to non-load-bearing applications. Recent advancements in nanoscience and nanotechnology have reignited investigation of HAp formation in the nanorange to clearly define small-scale properties of HAp. It has been suggested that nano- HAp may be an ideal biomaterial due to its good biocompatibility and bone integration ability. In this chapter, a new view on nano-HAp particles highlights the importance of size, crystal morphology controls, and composites with other inorganic particles in the application of biomedical material development. We have also reviewed nanosized HAp-based highly porous composite materials used for bone tissue engineering, introduced various fabrication methods used to prepare nHAp/polymer composite scaffolds, and characterized these scaffolds on the basis of their biodegradability and biocompatibility through in vitro or in vivo tests. Finally, we provide a summary and our own perspectives on this active area of research.