Compounding of glass fiber-reinforced polypropylene and investigation of its mechanical properties under simple and complex loading

Polypropylene is one of the important thermoplastics that has been reinforced with glass fibers to give a reasonably good engineering plastic. Because of its inert nature, it does not easily adhere to the glass surface and hence some improvement in mechanical properties. In the present study a vinyltriethoxysilane coupling agent in polymeric form has been tried and seen to improve the properties. Tests have been carried out at (a) constant strain rate (in the Instron testing machine), and (b)constant stress rate (water loading on a biaxial testing machine). Under constant strain rate only tensile properties have been studied while under constant stress rate, the tensile, torsional and combined tensile-torsional tests have been carried out. In each of the above cases, a considerable improvement in elastic modulus has been observed. The Tensile strength is improved to the extent of about 25 percent. There is only a slight improvement in torsional strength. Different fiber volume contents were used and their effect studied on modulus and strength. The mechanical data for reinforced-polypropylene samples have been discussed in terms of the fiber-length distribution in the composite. Detailed analysis of tensile data suggests that at low strains, when the critical length is relatively low, the fibers contribute to a high modulus. With increasing strain the critical length increases and the load carrying capacity of the fibers is reduced. Consequently the gain in strength is relatively less. The effect of fiber length distribution in torsion and combined tension-torsion tests would be expected to be similar and the results seem to confirm this.     

Graphene Oxide Attenuates Toxicity of Amyloid-β Aggregates in Yeast by Promoting Disassembly and Boosting Cellular Stress Response

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease, with the aggregation of misfolded amyloid-β (Aβ) peptides in the brain being one of its histopathological hallmarks. Recently, graphene oxide (GO) nanoflakes have attracted significant attention in biomedical areas due to their capacity of suppressing Aβ aggregation in vitro. The mechanism of this beneficial effect has not been fully understood in vivo. Herein, the impact of GO on intracellular Aβ42 aggregates and cytotoxicity is investigated using yeast Saccharomyces cerevisiae as the model organism. This study finds that GO nanoflakes can effectively penetrate yeast cells and reduce Aβ42 toxicity. Combination of proteomics data and follow-up experiments show that GO treatment alters cellular metabolism to increases cellular resistance to misfolded protein stress and oxidative stress, and reduces amounts of intracellular Aβ42 oligomers. Additionally, GO treatment also reduces HTT103QP toxicity in the Huntington's disease (HD) yeast model. The findings offer insights for rationally designing GO nanoflakes-based therapies for attenuating cytotoxicity of Aβ42, and potentially of other misfolded proteins involved in neurodegenerative pathology.     

Fabrication of CeO2 microspheres by internal gelation process using flow-focusing droplet generator

Sphere-pac fuel is an alternative nuclear fuel technology in which microspheres of two or more sizes are utilized to fill the cladding tube in place of the more conventional single-size fuel pellets. This provides leeway for adjusting the fuel pellet packing density and resulting cladding tube porosity. The current investigation makes use of a flow-focusing droplet generator made from stainless steel (S.S.) 316 L, with a channel internal diameter (I.D.) of 0.5, 0.8, 1, and 3 mm. These microspheres were supposed to be of actinide oxide but here, cerium has been chosen as a surrogate of plutonium. Detailed information about the flow-focusing droplet generator, internal gelation process, and sphere-pac fuel has been provided. The size and size distribution of ceria microspheres were investigated by varying the flow rates of the continuous and dispersed phase. The characterization of ceria microspheres has been conducted using techniques such as scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) analyses. The size of prepared monodisperse microspheres was controlled precisely (within ±2%) in the range of 498–2888 μm using four S.S. 316 L flow-focusing droplet generators with channel I.D. 0.5, 0.8, 1, and 3 mm, respectively, and the coefficient of variation of the size distribution was found to be less than 2%.     

Flow physics of planar bistable fluidic oscillator with backflow limbs

Fluidic oscillators (FOs) are used in a variety of applications, including process control and process intensification. Despite the simple design and operation of FOs, the fluid dynamics of FOs exhibit rich complexities. The inherently unstable flow, jet oscillations, and resulting vortices influence mixing and other transport processes. In this work, we computationally investigated the fluid dynamics of a new design of a planar FO with backflow limbs. The design comprised of two symmetric backflow limbs leading to bistable flow. The unsteady flow dynamics, internal recirculation, jet oscillations, secondary flow vortices were computationally studied over a range of inlet Reynolds numbers (2400–12,000). The nature and frequency of the jet oscillations were quantified. The computed jet oscillation frequency was compared with the experimentally measured (using imaging techniques) jet oscillation frequency. The flow model was then used to quantitatively understand mixing, heat transfer, and residence time distribution. The approach and the results presented in this work will provide a basis for designing FO's with desired flow and transport characteristics for various engineering applications.     

Comparison of the Microstructures and Mechanical Properties in the Overlapping Region of Low Carbon Steel Additive Bead Fabricated by WAAM and FSP

Metallurgical and Materials Transactions A - The periodic structural characteristics of the grains in the overlapping region of the WAAM deposited additive bead translate into spatially dependent...     

Molding and torsional testing of tubular specimens of glass fiber-reinforced polypropylene

This paper describes a torsion pendulum based on the free vibration method and designed for studies on tubular samples. The design and fabrication of the injection mold used for molding the tubular specimens is also described. Tubular specimens were injection molded form polypropylene and glass fiber-reinforced polypropylene having different glass fiber contents. The sample, which is enclosed in an insulated chamber, can be cooled with the help of liquid nitrogen and heated electrically. The damped oscillations were recorded on a moving chart paper using a lamp and a photodyne between −40 to 100°C. The results indicate that both storage modulus and the logarithmic decrement are affected by the glass fiber and its content. The reinforcing effect of glass fiber and the suppression of viscoelastic effects are briefly discussed.