Study of reinforcement distribution, adhesion between layers, and porosity induced by FDM

This study aims to understand the distribution of reinforcement material in the matrix, evaluate the adherence between layers, and determine the air gap between printing roads. We printed the specimen with two different composite materials, Polylactic Acid (PLA) reinforced with acrylic particles, and another filament reinforced with short carbon fibers. For the observations of the samples, we used a Confocal Microscope. We estimated the porosity of the material by comparing the expected mass with that achieved after manufacture. By pixel count, after binarization, we found the average percentage of acrylate particulate. They showed fair distribution through the PLA matrix even after the manufacturing process. The determination of fibers alignment was made by binarization of image, together with k-means and edge detection. This combination of methods allows estimating the fiber alignment by orientation straight lines. The manufacturing process did not offer good alignment of the fibers, even with the filament initially well aligned

An optimized hybrid rocket motor for the SARA platform reentry system

This paper has described a system design process, based on a multidisciplinary optimization technique, of a conceptual optimized hybrid propellant rocket motor. The proposed engine could be a technological option for the reentry maneuvering system of the Brazilian recoverable satellite (SARA), which was designed by the Brazilian Institute of Aeronautics and Space. The resulting optimized propulsion system must be viewed as a proof of concept allowing comparison to more conventional technologies, i.e., liquid and solid motors. Design effort was conducted for hybrid propellants engines based on a liquefying fuel (solid paraffin) and two different oxidizers, H2O2 (90% high-testperoxide) and self-pressurizing N2O. The multidisciplinary configuration optimization technique was supported on geometrical operating parameters of the motor, rather than on performance, in order to facilitate subsequent design and fabrication. Results from the code presented a hybrid motor, which was considered a competitive alternative for the deboost engine when compared to the traditional chemical systems, solid and liquid bipropellant, and monopropellant. The estimated mass of the reentry system, for the cases addressed in this study, varied from 22 to 29 kg, which is lower than either liquid bipropellant or solid engines formerly proposed

EVALUATION OF THE STRUCTURAL BEHAVIOR OF ALUMINUM HONEYCOMB SANDWICH PANELS FOR MICROSATELLITES

This work has as target the analysis of honeycomb structures by applying analytical models and numerical simulation that employ different finite element approaches: solid model for panel with equivalent honeycomb core properties, solid model of the honeycomb core and faces, and surface model of the honeycomb core and faces. There is also the standard test method for determination of the bending and shear properties of honeycomb sandwich samples whose results are employed for validation purposes. Thus, the main interest is to study the deformation of the honeycomb structures under shear load to devise a methodology to facilitate their design and manufacture. The prediction of the structural behavior of satellite components at real conditions of operation as well as the quality assessment of their manufacturing process requires this preliminary stress-strain evaluation of honeycomb sandwich panel samples. In this work, several tests were performed to access the behavior of the honeycomb structures and the results are consistent to the literature

PRELIMINARY EVALUATION OF STRUCTURAL INTEGRITY OF THE SINGLE-PORT HDPE AND PARAFFIN GRAIN UNDER LOW TEMPERATURE CONDITIONS

The main aim of the paper is to verify the feasibility of application of such  common materials as paraffin and polyethylene for a small-sized single-port fuel grain in hybrid rocket motors at low temperature conditions. The simplified analytical method of stress analysis had been used to calculate the stresses in the grain and afterwards was verified with results obtained by the finite element method. The results of calculation and simulation revealed that the structural integrity of the paraffin at low temperatures is in doubt, while the polyethylene may carry the loads induced by cold conditions

NEOTROPICAL XENARTHRANS: a data set of occurrence of xenarthran species in the Neotropics

Xenarthrans—anteaters, sloths, and armadillos—have essential functions for ecosystem maintenance, such as insect control and nutrient cycling, playing key roles as ecosystem engineers. Because of habitat loss and fragmentation, hunting pressure, and conflicts with domestic dogs, these species have been threatened locally, regionally, or even across their full distribution ranges. The Neotropics harbor 21 species of armadillos, 10 anteaters, and 6 sloths. Our data set includes the families Chlamyphoridae (13), Dasypodidae (7), Myrmecophagidae (3), Bradypodidae (4), and Megalonychidae (2). We have no occurrence data on Dasypus pilosus (Dasypodidae). Regarding Cyclopedidae, until recently, only one species was recognized, but new genetic studies have revealed that the group is represented by seven species. In this data paper, we compiled a total of 42,528 records of 31 species, represented by occurrence and quantitative data, totaling 24,847 unique georeferenced records. The geographic range is from the southern United States, Mexico, and Caribbean countries at the northern portion of the Neotropics, to the austral distribution in Argentina, Paraguay, Chile, and Uruguay. Regarding anteaters, Myrmecophaga tridactyla has the most records (n = 5,941), and Cyclopes sp. have the fewest (n = 240). The armadillo species with the most data is Dasypus novemcinctus (n = 11,588), and the fewest data are recorded for Calyptophractus retusus (n = 33). With regard to sloth species, Bradypus variegatus has the most records (n = 962), and Bradypus pygmaeus has the fewest (n = 12). Our main objective with Neotropical Xenarthrans is to make occurrence and quantitative data available to facilitate more ecological research, particularly if we integrate the xenarthran data with other data sets of Neotropical Series that will become available very soon (i.e., Neotropical Carnivores, Neotropical Invasive Mammals, and Neotropical Hunters and Dogs). Therefore, studies on trophic cascades, hunting pressure, habitat loss, fragmentation effects, species invasion, and climate change effects will be possible with the Neotropical Xenarthrans data set. Please cite this data paper when using its data in publications. We also request that researchers and teachers inform us of how they are using these data