Effect of raster angle on mechanical properties of 3D printed short carbon fiber reinforced acrylonitrile butadiene styrene

The most common additive manufacturing technique fused filament fabrication (FFF) suffers from inter-bead porosity that reduces mechanical properties. Inter-bead pores follow the raster angle, which causes anisotropic mechanical properties. Yet, the effects of raster angle on the mechanical behavior of short-carbon-fiber-reinforced (SCFR) thermoplastics are unclear. In this study, we performed tensile, flexural, and fracture toughness tests on SCFR acrylonitrile butadiene styrene (ABS). Raster angles of 0°, 15°, 30°, 45°, 60°, 75°, and 90° were investigated. Tensile strength and elastic modulus decreased by 22–35% for a change from 0° to 15°. Flexural strength and modulus were less sensitive to raster angle. Flexural strengths were at least 50% more than tensile strength for the same raster angle. Whereas flexural modulus is at least 15% less than elastic modulus. Fracture toughness showed a non-linear relationship with the raster angle. Maximum fracture toughness was observed at 0° and 60° rasters. Crack deflection was observed as the toughening mechanism

Fused Deposition Modeling with Induced Vibrations: A Study on the Mechanical Characteristics of Printed Parts

The recent development of RepRap style 3D printers has made additive manufacturing technology available to the public at a low cost. While these 3D printers are being used for a variety of purposes, one of the main applications is prototyping in design projects. The quality of the 3D-printed parts has been a concern in such cases. Many variables within these printers’ operation can be varied to obtain optimum print quality. This study explores a setup that uses externally induced mechanical vibrations to the nozzle tip as a potential method to improve the quality of 3D-printed parts. Induced vibration is expected to decrease the porosity of printed parts and enhance the cohesion between print beads, ultimately improving their mechanical properties. The objective is to understand the prints’ positional accuracy, porosity, and mechanical properties with the added vibration and then to determine the optimum vibration level to achieve the best quality prints. While previous studies have explored the role of induced vibration on the mechanical properties of printed parts, the novelty of this work lies in the determination of the positional accuracy of those parts and the determination of optimum vibration levels to achieve desired properties. For positional accuracy, the extruder filament is replaced with a pointed-tip pen that can mark the exact location where the printer delivers the material. A comparison between the locations marked by the pen with and without vibrations shows that the errors induced by the added vibration are not significantly different from those caused by the uncertainties of the printer itself. Based on the tensile tests of the printed specimens, it is concluded that the parts printed with induced vibrations have improved mechanical properties. The printed parts’ porosity is reduced significantly due to the induced vibrations. Further, this study also explores the optimum motor speeds to achieve a uniform distribution of material. It determines medium motor speeds that provide a maximum vibration amplitude, which is more desirable for a consistent infill

Data on thermal conductivity and dynamic mechanical properties of graphene quantum dots in epoxy

Graphene Quantum Dots (GQDs) and epoxy have been combined into a nanocomposite and evaluated for their thermal and dynamic mechanical properties. Samples of varying GQD mass loading were first examined with SEM in several images. Thermal conductivity was estimated using Differential Scanning Calorimetry (DSC) with a step analysis technique and analysis program. Several dynamic mechanical properties were recorded using Dynamic Mechanical Analysis (DMA) and displayed in their raw and analyzed formats. For more insight please see Infusion of graphene quantum dots to modulate thermal conductivity and dynamic mechanical properties of polymers [1]

Pulmonary embolism presenting as syncope: a case report

<p>Abstract</p> <p>Introduction</p> <p>Despite the high incidence of pulmonary embolism its diagnosis continues to be difficult, primarily because of the vagaries of symptoms and signs in presentation. Conversely, syncope is a relatively easy clinical symptom to detect, but has varied etiologies that lead to a documented cause in only 58% of syncopal events. Syncope as the presenting symptom of pulmonary embolism has proven to be a difficult clinical correlation to make.</p> <p>Case presentation</p> <p>We present the case of a 26-year-old Caucasian man with pulmonary embolism induced-syncope and review the pathophysiology and diagnostic considerations.</p> <p>Conclusions</p> <p>Pulmonary embolism should be considered in the differential diagnosis of every syncopal event that presents at an emergency department.</p

A Hierarchical Approach for Creating Electrically Conductive Network Structure in Polyurethane Nanocomposites using a Hybrid of Graphene Nanoplatelets, Carbon Black and Multi-Walled Carbon Nanotubes

Hierarchical organization of carbon nanomaterials is the best strategy to combine desirable factors and synergistically impart mechanical and electrical properties to polymers. Here, we investigate the relaxation behavior of carbon nanofillers filled polyurethane (PU) with special reference to particle size and aspect ratio, filler morphology, filler loading to understand the conductive network formation of fillers in the PU matrix. Typically, an addition of 2 wt% hybrid fillers of graphene nanoplatelets (GNPs), conductive carbon black (CB) and multiwalled carbon nanotubes (MWCNTs) in PU at 1:1:2 mass ratio (GCM112-PU2) showed lowest surface resistivity ~106.8 ohm/sq along with highest improved mechanical properties. Our results demonstrate how hierarchical compositions may function in polymer configurations that are useful for thermal and electrical systems

Next Generation Sequencing Based Multiplex Long-Range PCR for Routine Genotyping of Autoinflammatory Disorders

Background: During the last decade, remarkable progress with massive sequencing has been made in the identification of disease-associated genes for AIDs using next-generation sequencing technologies (NGS). An international group of experts described the ideal genetic screening method which should give information about SNVs, InDels, Copy Number Variations (CNVs), GC rich regions. We aimed to develop and validate a molecular diagnostic method in conjunction with the NGS platform as an inexpensive, extended and uniform coverage and fast screening tool which consists of nine genes known to be associated with various AIDs. Methods: For the validation of basic and expanded panels, long-range multiplex models were setup on healthy samples without any known variations for MEFV, MVK, TNFRSF1A, NLRP3, PSTPIP1, IL1RN, NOD2, NLRP12 and LPIN2 genes. Patients with AIDs who had already known causative variants in these genes were sequenced for analytical validation. As a last step, multiplex models were validated on patients with pre-diagnosis of AIDs. All sequencing steps were performed on the Illumina NGS platform. Validity steps included the selection of related candidate genes, primer design, development of screening methods, validation and verification of the product. The GDPE (Gentera) bioinformatics pipeline was followed. Results: Although there was no nonsynonymous variation in 21 healthy samples, 107 synonymous variant alleles and some intronic and UTR variants were detected. In 10 patients who underwent analytical validation, besides the 11 known nonsynonymous variant alleles, 11 additional nonsynonymous variant alleles and a total of 81 synonymous variants were found. In the clinical validation phase, 46 patients sequenced with multiplex panels, genetic and clinical findings were combined for diagnosis. Conclusion: In this study, we describe the development and validation of an NGS-based multiplex array enabling the “long-amplicon” approach for targeted sequencing of nine genes associated with common AIDs. This screening tool is less expensive and more comprehensive compared to other methods and more informative than traditional sequencing. The proposed panel offers advantages to WES or hybridization probe equivalents in terms of CNV analysis, high sensitivity and uniformity, GC-rich region sequencing, InDel detection and intron covering

Modeling failure in brittle porous ceramics

Brittle porous materials (BPMs) are used for battery, fuel cell, catalyst, membrane, filter, bone graft, and pharmacy applications due to the multi-functionality of their underlying porosity. However, in spite of its technological benefits the effects of porosity on BPM fracture strength and Weibull statistics are not fully understood–limiting a wider use. In this context, classical fracture mechanics was combined with two-dimensional finite element simulations not only to account for pore-pore stress interactions, but also to numerically quantify the relationship between the local pore volume fraction and fracture statistics. Simulations show that even the microstructures with the same porosity level and size of pores differ substantially in fracture strength. The maximum reliability of BPMs was shown to be limited by the underlying pore–pore interactions. Fracture strength of BMPs decreases at a faster rate under biaxial loading than under uniaxial loading. Three different types of deviation from classic Weibull behavior are identified: P-type corresponding to a positive lower tail deviation, N-type corresponding to a negative lower tail deviation, and S-type corresponding to both positive upper and lower tail deviations. Pore-pore interactions result in either P-type or N-type deviation in the limit of low porosity, whereas S-type behavior occurs when clusters of low and high fracture strengths coexist in a fracture data

The Effect of Environmental Management Practices and Knowledge in Strengthening Responsible Behavior: The Moderator Role of Environmental Commitment

This study examines the effects of environmental management practices on environmental knowledge and environmentally responsible behavior by means of an environmental commitment moderator variable regarding the hotel employees in Manavgat–Türkiye. The existing literature on the relevant concepts has provided the theoretical basis of the research. Using the stratified convenience sampling method, a sample of 403 hotel employees from various hotels in the region participated in the survey. First of all, data screening analysis was used for the analysis of research data and the results obtained were analyzed through the AMOS program to test the structural model. According to the research results, it has been determined that environmental management practices are considered to be an important variable in terms of environmental knowledge and environmental knowledge positively affects the level of responsible behavior. In addition, it has been concluded that environmental commitment strengthens the relationship between these variables. In future research, it is predicted that the implementation of this study, which has been applied to hotel employees, in other areas of the tourism sector by taking into account the variables such as organizational commitment, business attachment, organizational performance, and employee attitude will enrich the literature

Fused Deposition Modeling with Induced Vibrations: A Study on the Mechanical Characteristics of Printed Parts

The recent development of RepRap style 3D printers has made additive manufacturing technology available to the public at a low cost. While these 3D printers are being used for a variety of purposes, one of the main applications is prototyping in design projects. The quality of the 3D-printed parts has been a concern in such cases. Many variables within these printers&rsquo; operation can be varied to obtain optimum print quality. This study explores a setup that uses externally induced mechanical vibrations to the nozzle tip as a potential method to improve the quality of 3D-printed parts. Induced vibration is expected to decrease the porosity of printed parts and enhance the cohesion between print beads, ultimately improving their mechanical properties. The objective is to understand the prints&rsquo; positional accuracy, porosity, and mechanical properties with the added vibration and then to determine the optimum vibration level to achieve the best quality prints. While previous studies have explored the role of induced vibration on the mechanical properties of printed parts, the novelty of this work lies in the determination of the positional accuracy of those parts and the determination of optimum vibration levels to achieve desired properties. For positional accuracy, the extruder filament is replaced with a pointed-tip pen that can mark the exact location where the printer delivers the material. A comparison between the locations marked by the pen with and without vibrations shows that the errors induced by the added vibration are not significantly different from those caused by the uncertainties of the printer itself. Based on the tensile tests of the printed specimens, it is concluded that the parts printed with induced vibrations have improved mechanical properties. The printed parts&rsquo; porosity is reduced significantly due to the induced vibrations. Further, this study also explores the optimum motor speeds to achieve a uniform distribution of material. It determines medium motor speeds that provide a maximum vibration amplitude, which is more desirable for a consistent infill

Realization of multiband microwave metamaterials fabricated via low-cost inkjet printing

We present design and computational analysis of multiband metamaterial structures that are fabricated via low-cost inkjet printing. In particular, three-dimensional arrangements of split-ring resonators with different sizes are considered to achieve bandstop characteristics at multiple frequencies. A fast and accurate solver is employed to analyze alternative arrangements, while considering different parameters to obtain strong resonances at desired frequencies. The obtained designs are fabricated in a low-cost inkjet-printing setup, which is based on using conventional printers that are modified and loaded with silver-based inks. Initial results shown in this paper demonstrate the feasibility of low-cost multiband metamaterials. © 2019 EuMCE