The effect of bimodal distribution on the mechanical properties of hydroxyapatite particle filled poly(L-lactide) composites

The effects of a bimodal distribution of micro-HA and nano-HA particles on the mechanical properties such as bending strength, modulus and mode I fracture energy of HA/PLLA composites were investigated. The bending properties were effectively improved by a bimodal distribution compared to a monomodal distribution. It is considered that in the bimodal HA/PLLA, the PLLA molecular chains are constrained by the existence of well distributed nano-particles, resulting in the reduction of the deformation of molecular chains. The mode I fracture energy was also effectively improved by a bimodal distribution with additional energy dissipation mechanisms, that is, dense ductile deformation of the PLLA matrix and debonding of the particle/matrix interfaces in the crack-tip region.