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.

In contrast to subtractive manufacturing techniques, additive manufacturing processes are known for their high efficiency in regards to utilisation of feedstock. However the various polymer, metallic and composite feedstocks used within additive manufacturing are mainly derived from energy consuming, inefficient methods, often originating from non-sustainable sources. This work explores the mechanical properties of additively manufactured composite structures fabricated from recycled sustainable wood waste with the aim of enhancing mechanical properties through glass fibre reinforcement.In the first instance, samples were formed by pouring formulation of wood waste (wood flour) and thermosetting binder (urea formaldehyde), with and without glass fibres, into a mould. The same formulations were used to additively manufacture samples via a layered deposition technique. Samples manufactured using each technique were cured and subsequently tested for their mechanical properties. Additively manufactured samples had superior mechanical properties, with up to 73% increase in tensile strength compared to moulded composites due to a densification of feedstock/paste and fibre in-situ directional alignment

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.

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.