Reinforcing strategy by adding nano- and/or micro-scale fillers leads to enhanced not only mechanical properties of 3D-printed parts but also viscoelastic properties such as creep behavior. To characterize this complex creep behavior of composite materials, viscoelastic mathematical models are used combined with experimental data. As a preliminary study, neat polyetherimide (PEI) and 5, 10, 20 wt.% CB reinforced PEI composite filaments were fabricated in the co-rotating twin-screw extruder. After rheological examinations, dynamic mechanical analysis (DMA) samples were printed by a custom-made 3D printer to realize creep analysis. In this study, the Burgers model and the empirical Findley power-law model were employed to simulate the experimental creep data. Both of the models were able to simulate the experimental data in good agreement. However, the Burgers model could not capture the elastic instantaneous strain but the Findley power-law model gave more agreed curve fits.
The work study the landing of a spacecraft on the Jupiter satellite Callisto with minimal energy costs, and the minimum required thrust of the engines and the duration of the soft landing maneuver of a spacecraft with a given mass on the satellite were estimated. A distinctive feature of this study is taking into account the weak atmosphere of Callisto, which, however, in the immediate vicinity of the surface has a noticeable aerodynamic drag. Motion modeling was carried out numerically; all the graphical dependencies necessary for motion analysis were built.
The aim of this study is to utilize the Dynamic Mode Decomposition with Control (DMDc), a data-driven model discovery technique, to obtain a model for the lateral-directional motion of a highly maneuverable aircraft for the purpose of implementing integral action based Model Predictive Control (MPC). The model's ability to withstand noisy conditions is evaluated, and its practicality is assessed by analyzing its computational requirements. The computational time and storage requirements are assessed under minimal system requirements. Real-time testing on Speedgoat equipment indicates that the DMDc-MPC algorithm has low computational costs and is suitable for systems with limited computational power and portability.
In this study, the aerodynamic performance of the flapping owl, eagle and S1223 airfoils was investigated numerically using ANSYS Fluent commercial CFD code. The study was carried out by solving Reynolds Averaged Navier Stoke (RANS) equations where the turbulence was modeled by k-Epsilon turbulence model. The moving mesh strategy was adapted for the airfoil flapping. The numerical results were obtained for a Reynolds number of $7\times 10^{5}$ and a flapping rate of $\mp 0. 5\frac{rad}{s}$ . The results were presented in terms of pressure contours, streamlines, time history fluctuation of the lift and drag coefficients and aerodynamic efficiency. The downstroke and upstroke pressure contours and streamlines show similar aerodynamic behavior for the studied airfoils. The only differences are the size and the location of vortices. In comparison to the S1223 airfoil, the results showed that the eagle and owl airfoils generated more lift during the downstroke mode and less lift during upstroke mode. In terms of aerodynamic efficiency, eagle's airfoil generates the highest lift to drag ratio followed by S1223 airfoil. The obtained results showed good agreement with the published results in terms of the time history fluctuation trend for the lift and drag coefficients.
This paper presents guidelines on the use of a characterization diagram for impact dynamics scaling and damage tolerance studies for aerospace structures. It is demonstrated that the diagram obtained for rigid impactors, can also be used for deformable impactors such as hail and bird strikes. By placing the impact response on the diagram useful information on the type of response and damage can be predicted prior to running experiments or simulations. It is expected that this methodology could be a very powerful tool to designers and experimentalists who work in the area of design and commissioning for damage resistance and tolerance especially with composite structures.
