Improvement of fracture energy of HA/PLLA biocomposite material due to press processing
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Much attention has recently been paid to poly (l-lactic acid) (PLLA) as a biomaterial, mainly owing to its bioabsorbability and biocompatibility. For example, PLLA has widely been used for bone fixation devices in orthopedic and oral surgeries. Recently, different types of hydroxyapatite (HA) filled PLLA composite materials have been developed to improve the bioactivity of such orthopedic implants, and their structures and mechanical properties were investigated [1, 2, 3, 4, 5, 6, 7, 8, 9]. Todo et al. recently reported that HA addition dramatically reduced the mode I fracture property of the neat PLLA mainly because of the weak interfacial bonding between PLLA and HA particles [8, 9]. On the other hand, drawing process is known to be an effective way to improve the fracture properties such as strength and fracture toughness of thermoplastics and just recently, unidirectional drawing was applied to PLLA and dramatic improvement of mode I fracture property was reported ...