Fabrication of Biodegradable Fiber Reinforced Ti Functionally Graded Materials and Their Wear Properties

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Ti and Ti alloys are particularly attractive materials as the metallic implant-material. This is because that these alloys have low shear modulus and the good biological compatibility with bone. However, interfacial adhesion ability of bone and Ti alloy is low. As improvement method of the interfacial adhesion ability, bioaffinity material like hydroxyapatite has been coated on surface of the Ti alloys. However, such bioaffinity materials have low strength and wear resistance. In this study, Ti composites containing biodegradable poly-L-lactic-acid (PLLA) fiber were fabricated by spark plasma sintering (SPS) method. The PLLA fiber plays a role as reinforcement in Ti matrix, and can be gradually decomposed inside body with progress of time. By the decomposition of PLLA, pore is generated in Ti matrix, and bone simultaneously penetrates into the pore. Therefore, tightly bond between bone and Ti matrix can be expected. Using the Ti-PLLA composites fabricated by SPS method, microstructural observation and mechanical tests were performed. It was found that Ti-PLLA composite has laminate-layer structure with plate-like shape PLLA. Hardness and wear behavior of Ti-PLLA composite has anisotropy due to its structure. However, strength of the Ti-PLLA composite is low because of the imperfect sintering of Ti matrix. Since sintering of Ti matrix can be improved by changing the temperature of SPS, Ti-PLLA composite with anisotropic mechanical properties can be expected by SPS method.