Characterization of bending behavior of hydroxyapatite/biopolymer porous composite beams

In this work, porous composite beams of HA/PLLA and HA/PLCL were developed using a combination of the template and freeze-drying methods. Their compositions were examined using Fourier transform infrared spectroscopy and X-ray diffraction spectroscopy. Their bending mechanical and fracture properties were characterized under the three-point bending condition. Their microstructures and the micro mechanisms of deformation and fracture were also examined by scanning electron microscopy. It was confirmed that the presence of polymer material did not affect the crystal structure of HA, and the diffraction pattern of both beams remained the same after sintering. Both composite beams showed dramatically improved flexural mechanical properties compared to a pure HA beam. Their bending fracture behavior was characterized as a crack initiation and growth accompanied by microdamage formation at the center. It was determined that microdamage formation and the subsequent deformation and fracture of the polymer phase was initiated by microfracture of HA struts. It was also found that the addition of PLLA results in a higher modulus and fracture strength, while the addition of PLCL results in a higher fracture energy due to ductile elongation.