Purpose -The purpose of this paper was to investigate the feasibility on design and production of a three-dimensional honeycomb based on selective laser melting (SLM) technique for use in aeronautical application. Design/methodology/approach -Various polyhedrons were investigated using their mechanical property, i.e. strain energy density (SED), by means of finite element (FE) analysis for the suitability of use in aerospace application; the highest SED polyhedron was selected as a candidate polyhedron. From the FE analysis, the truncated octahedron (three-dimensional honeycomb) structure was considered to be the potential candidate. Polyhedron size and beam thickness of the open-cellular three-dimensional honeycomb structure were modelled and analysed to observe how the geometric properties influence the stiffness of the structure. One selected model of open-cellular honeycomb (unit cell size: 2.5 mm and beam thickness: 0.15 mm) was fabricated using SLM. The SLM prototypes were assessed by their mechanical properties, including compressive strength, stiffness and strength per weight ratio. To investigate the feasibility in production of airfoil section sandwich structure, NACA 0016 airfoil section with three-dimensional honeycomb core was constructed and also fabricated using SLM. Findings -According to the result, the three-dimensional honeycomb has elastic modulus of 63.18 MPa and compressive strength of 1.1 MPa, whereas strength per weight ratio is approximately 5.0 ϫ 103 Nm/kg. The FE result presented good agreement to the mechanical testing result. The geometric parameter of the three-dimensional honeycomb structure influences the stiffness, especially the beam thickness, i.e. increase of beam thickness obviously produces the stiffer structure. In addition, the sandwich structure of airfoil was also successfully manufactured. Originality/value -This work demonstrated the production of sandwich structure of airfoil using SLM for aeronautical engineering. This investigation has shown the potential applications of the three-dimensional structure, e.g. aircraft interior compartment components and structure of unmanned aerial vehicles.

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The fabrication of hydroxyapatite scaffolds for bone tissue engineering applications by using lithography-based additive manufacturing techniques has been introduced due to the abilities to control porous structures with suitable resolutions. In this research, the use of hydroxyapatite cellular structures, which are processed by lithography-based additive manufacturing machine, as a bone tissue engineering scaffold was investigated. The utilization of digital light processing system for additive manufacturing machine in laboratory scale was performed in order to fabricate the hydroxyapatite scaffold, of which biocompatibilities were eventually evaluated by direct contact and cell-culturing tests. In addition, the density and compressive strength of the scaffolds were also characterized. The results show that the hydroxyapatite scaffold at 77% of porosity with 91% of theoretical density and 0.36 MPa of the compressive strength are able to be processed. In comparison with a conventionally sintered hydroxyapatite, the scaffold did not present any cytotoxic signs while the viability of cells at 95.1% was reported. After 14 days of cell-culturing tests, the scaffold was able to be attached by pre-osteoblasts (MC3T3-E1) leading to cell proliferation and differentiation. The hydroxyapatite scaffold for bone tissue engineering was able to be processed by the lithography-based additive manufacturing machine while the biocompatibilities were also confirmed.

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The laser powder bed fusion (L-PBF) process is a powder-based additive manufacturing process that can manufacture complex metallic components. However, when the metallic components are fabricated with the L-PBF process, they frequently encounter the residual stress and distortion that occurs due to the cyclic of rapid heating and cooling. The distortion detrimentally impacts the dimensional and geometrical accuracy of final built parts in the L-PBF process. The purpose of this research was to explore and predict the distortion of Ti-6Al-4V components manufactured using the L-PBF process by using numerical modeling in Simufact Additive 2020 FP1 software. Firstly, the numerical model validation was conducted with the twin-cantilever beam part. Later, studies were carried out to examine the effect of component sizes and support-structure designs on the distortion of tibial component produced by the L-PBF process. The results of this research revealed a good agreement between the numerical model and experiment data. In addition, the platform was extended to predict the distortion in the tibial component. Large distortion arose near the interface between the tibial tray and support structure due to the different stiffness between the solid bulk and support structure. The distortion of the tibial component increased with increasing component size according to the surface area of the tibial tray, and with increasing thickness of the tibial tray. Furthermore, the support-structure design plays an important role in distortion reduction in the L-PBF process. For example, the maximum distortion of the tibial component was minimized up to 44% when a block support-structure design with a height of 2.5 mm was used instead of the lattice-based support. The present study provides useful information to help the medical sector to manufacture effective medical components and reduce the chance of part failure from cracking in the L-PBF process.