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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.