Key Engineering Materials Vol. 956

Abstract: Additive Manufacturing (AM) has been one of the technologies that has been booming in recent years. Its main advantages are the versatility in the manufacture of parts, the ability to print limited series and its low acquisition cost, among others. Among these technologies, one of the most widely used by engineering and product design teams is Fused Filament Fabrication (FFF). PLA being one of the materials most employed for FFF. Likewise, for a proper shaping of this material and process, it is necessary to establish several parameters to define the quality and properties of the designed part. In this context, a comparison of two groups of pieces has been carried out. Whereas the first group exhibits a correct process parameters and an adequate calibration of the printing bed; the second, has not any bonding between layers or bonding of beads of the same layer, due to an incorrect establishment of the initial parameters. In order to compare these groups, a study of the internal structure was carried out by X-Ray CT along with a characterization of their tensile mechanical properties. Results show a similar maximum stress for both groups, but a drastic reduction of the plastic area in the parts with defects. The quantification and comparison of the mechanical properties of both tests might provide a rejection criterion for parts that work in tension and present defects similar to those studied for engineering teams in product design.

Abstract: In recent years, materials with both waterproof and breathability have also been marked with the eye-catching slogan of "waterproof-breathable" on the commodity such as personal protective equipment or sportswear. Regarding the application of nanofiber non-woven fabric as waterproof and breathable materials for functional textile, although there are previous reports regarding conventional micro-fabrics, the relationship between the compositions of the fiber aggregate, waterproof and breathable properties remain unclear regarding nanofabrics. Therefore, this study shows investigation of influence of fiber diameter, bulk density and thickness of the woven nanofabric on waterproof-breathable ability with experiment and CFD (computational fluid dynamics) model. As a result, the average fiber diameters, bulk densities, and thicknesses to achieve waterproofness and air permeability were numerically obtained respectively. From the results, it can be found that, these parameters can be used as a reference for manufacturing high-performance waterproof permeable materials with both high waterproofness and high air permeability.

Abstract: Space traveling, extra-planetary exploration and even colonization requires to replicate our capabilities of manufacturing under non-entirely known environments and conditions. With the recent, yet always present, interest on colonizing spaces like the Moon or even Mars, space-based Additive Manufacturing (AM) has been considered for enabling space inhabitants to build their own tools. However, the same manufacturing techniques that are commonly used on Earth are not entirely applicable in space, especially during the considerably long traveling stage. Thus, several works have reported the study of how AM could be used in microgravity or near-zero g conditions by using the International Space Station as a laboratory. Unfortunately, the costs for doing such experiments are prohibitive, which is why experimentation in microgravity conditions on Earth is promising. In this paper, we explore the possibility of applying light-sensitive resin under Microgravity conditions using a Drop Tower facility and we propose a microgravity liquid printing technique. Our preliminary experiments focused on studying movement and extrusion velocities, extrusion nozzle diameter, UV light power, extrusion, and solidification times. The experimental runs (one catapult launch and four drops) let us find promising, although not entirely conclusive, data and practices to be considered in future works using this methodology. As expected, there is a similarity to liquid extrusion on Earth given that the initial shape and speed of extrusion influences the liquid material. Our findings also suggest that an initial contact point would help to increase the contact force due to surface tension and that the extrusion and solidification times are less than 5 seconds, which implies faster printing processes than in earth gravity conditions because the microgravity provides us less layer mixing during extrusion. The hardware, material and Microgravity drop tests used confirm the feasibility of this technique and they become an initial step for this printing process and liquid materials.

Abstract: This research focuses on compressive strength of concrete containing different percentages of municipal waste clam shell powder (CSP). The amount of cement is replaced by 5%, 10% and 15% of CSP. The result obtained shows that the compressive strength increases with the CSP content. Concrete containing 15%CSP has lower compressive strength compared to those containing 5% and 10%CSP. The concrete containing 15%CSP is almost similar to the control concrete (with zero CSP).

Abstract: In this study eggshells and low density polyethylene plastic (LDPE) wastes were reused to produce tiles. The eggshells were ground in a laboratory scale jar mill into the particle size of fine sand. The optimum grinding parameters were determined to be the setting that produced the highest mass of eggshell powder that was within the desired particle diameter size range of 0.425 mm (No. 40) and 0.075 mm (No. 200). A two to the three factorial design of experiment was used with variables of Time, Speed, and Ball Filling Ratio. The high and low values used in this study were 20 minutes and 10 minutes for the time, 250 rpm and 100 rpm for the speed, and 35% and 20% for the ball filling ratio. There were eight settings made with 3 trials per setting and one validation for the optimal setting produced. The eggshell powder produced by the optimal setting of the jar mill was used to create the LDPE-eggshell tiles. Four tiles were made for the three trials and for the validation part. The tiles were tested for its relative strength using the Compression Testing Machine. The researchers determined that eggshells and LDPE plastics may be formed into tiles and that the strength of the tiles that were produced by these materials exceeded the standard value set for this type of product.