High porosity composite structures produced from poly(lactic acid)/ hydroxyapatite microspheres using novel Dual Beam Laser Sintering method: Analysis of structural, mechanical and thermal properties

The paper discusses the applicability of the novel Dual Beam Laser Sintering (DBLS) method for processing of poly(lactic acid)/hydroxyapatite (PLA/HAp) composite powders. The composite microspheres were prepared using the solid-in-oil-in-water (S/O/W) emulsification technique. The three-dimensional structures made of composite microspheres with different filler content - 5 % and 10 % by weight of HAp were processed using DLBS that uses a new method of preheating the powder bed. The obtained results were compared to the case of pure PLA presented in our previous work. The quality of the powders was determined using Dry Laser Diffraction (DLS), X-Ray Computed Tomography (XCT), Revolution Powder Analysis (RPA) and Differential Scanning Calorimetry (DSC). The melt flow rate and the thermal conductivity of the microspheres were also determined. Conducted research shows that the morphology of the particle depends heavily on the HAp content which ultimately influences the powder flow -ability properties. Moreover, the properties of samples manufactured using DBLS were evaluated. The internal microstructure was reconstructed using XCT and the open porosity structures were revealed. The influence of both the porosity and the HAp reinforcement on the mechanical properties was observed. Additionally, a thermal DSC analysis was carried out, which allowed to assess how the filler and process parameters affect the degree of crystallinity of the obtained structures and the thermal degradation of the composite.In general, the presented study shows the possibility of designing part properties not only by means of the DBLS process parameters but also by influencing the powder material properties. Both raw material properties and process parameters affect the morphology of pores and therefore the mechanical properties of PBF processed material.