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Polymer matrices are usually reinforced with fibres giving a good strength/weight ratio. Currently, innovative research has been focussed in producing new composite materials using natural fibres as an alternative sustainable material. In the present work, the mechanical behaviour of a composite based on polylactic acid reinforced with bamboo fibre produced by additive manufacturing was evaluated. Specimens were manufactured using fused deposition modelling with different geometry depositions, layer thicknesses and fill densities. The results were evaluated performing an analysis of variance with a confidence level of 95%. The composites were subjected to mechanical testing to evaluate the influence of process parameters in tensile strength, strain, and elastic modulus. It was observed that the principal factors that influence the elasticity are the deposition geometry and fill density. Fracture zones and manufacturing defects were additionally studied using optical and scanning electron microscopy. The vertical orientation of the layers causes the premature rupture of the test samples due to the tension being reverted at the interface between the layers. The specimens showed slight adhesion between the polylactic acid matrix and the bamboo fibres. This effect was related with the presence of porosity, cracks and local deformations in the composite material.

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Purpose An experimental and numerical study of thermal profiles of 316 L stainless steel during selective laser melting (SLM) was developed. This study aims to present a novel approach to determine the significance and contribution of thermal numerical modeling enhancement factors of SLM. Design/methodology/approach Surface and volumetric heat models were proposed to compare the laser interaction with the powder bed and substrate, considering the powder size, absorptance and propagation of the laser energy through the effective depth of the metal layer. The approach consists in evaluating the contribution of the thermal conductivity anisotropic enhancement factors to establish the factors that minimized the error of the predicted results vs the experimental data. Findings The level of confidence of the carried-out analysis is of 97.8% for the width of the melt pool and of 99.8% for the depth of the melt pool. The enhancement factors of the y and z spatial coordinates influence the most in the predicted melt pool geometry. Research limitations/implications Nevertheless, the methodology presented in this study is not limited to 316 L stainless steel and can be applied to any metallic material used for SLM processes. Practical implications This study is focused on 316 L stainless steel, which is commonly used in SLM and is considered a durable material for high-temperature, high-corrosion and high-stress situations. Social implications The additive manufacturing (AM) technology is a relatively new technology becoming global. The AM technology may have health benefits when compared to the conventional industrial processes, as the workers avoid extended periods of exposure present in conventional manufacturing. Originality/value This study presents a novel approach to determine the significance and contribution of thermal numerical modeling enhancement factors of SLM. It was found that the volumetric heat model and anisotropic enhancement thermal approaches used in the present research, had a good agreement with experimental results.

This paper focuses on the aerodynamics and design of an unmanned aerial vehicle (UAV) based on solar cells as a main power source. The procedure includes three phases: the conceptual design, preliminary design, and a computational fluid dynamics analysis of the vehicle. One of the main disadvantages of an electric UAV is the flight time; in this sense, the challenge is to create an aerodynamic design that can increase the endurance of the UAV. In this research, the flight mission starts with the attempt of the vehicle design to get at the maximum altitude; then, the UAV starts to glide and battery charge recovery is achieved due to the solar cells. A conceptual design is used, and the aerodynamic analysis is focused on a UAV as a gliding vehicle, with the calculations starting with the estimation of weight and aerodynamics and finishing this stage with the best glide angle. In fact, the aerodynamic analysis is obtained for a preliminary design; this step involves the wing, fuselage, and empennage of the UAV. In order to achieve the preliminary design, an estimation of aerodynamic coefficients, along with computational fluid dynamics analysis, is performed.

Purpose A key challenge found in additive manufacturing is the difficulty to produce components with replicable microstructure and mechanical performance in distinct orientations. This study aims to investigate the influence of build orientation on the fracture toughness of additively manufactured AlSi10Mg specimens. Design/methodology/approach The AlSi10Mg specimens were manufactured using the selective laser melting (SLM) technology. The fracture toughness was experimentally determined (under ASTM E399-09) using C(T) specimens manufactured in different orientations. The microstructure of the specimens was examined using metallography to determine the effects of grain orientation on fracture toughness. Findings The fracture toughness magnitude of manufactured specimens ranged between 36 and 50 MPam, which closely matched conventional bulk material and literature values regarding AlSi10Mg components. The C(T) specimens printed in the T-L orientation yielded the highest fracture toughness. The grain orientation and fracture toughness values confirm the anisotropic nature of SLM parts where the T-L-oriented specimen obtained the highest KIC value. A clear interaction between the melt pool boundaries and micro-slipping during the loading application was observed. Originality/value The novelty of this paper consists in elucidating the relationship between grain orientation and fracture toughness of additively manufactured AlSi10Mg specimens because of the anisotropy generated by the different melting pool boundaries and orientations in SLM. The findings show that melt pool boundaries can behave as easier pathways for cracks to propagate and subsequently reduce the fracture toughness of specimens with cracks perpendicular to the build direction.

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The growth of additive manufacturing processes has enabled the production of complex and smart structures. These fabrication techniques have led research efforts to focus on the application of cellular materials, which are known for their thermal and mechanical benefits. Herein, we studied the mechanical behavior of stainless-steel (AISI 316L) lattice structures both experimentally and computationally. The lattice architectures were body-centered cubic, hexagonal vertex centroid, and tetrahedron in two cell sizes and at two different rotation angles. A preliminary computational study assessed the deformation behavior of porous cylindrical samples under compression. After the simulation results, selected samples were manufactured via laser powder bed fusion. The results showed the effects of the pore architecture, unit cell size, and orientation on the reduction in the mechanical properties. The relative densities between 23% and 69% showed a decrease in the bulk material stiffness up to 93%. Furthermore, the different rotation angles resulted in a similar porosity level but different stiffnesses. The simulation analysis and experimental results indicate that the variation in the strut position with respect to the force affected the deformation mechanism. The tetrahedron unit cell showed the smallest variation in the elastic modulus and off-axis displacements due to the cell orientation. This study collected computational and experimental data for tuning the mechanical properties of lattice structures by changing the geometry, size, and orientation of the unit cell.