Simulation‐aided development of a robust thermoclinching joining process for hybrid structures with textile reinforced thermoplastic composites and metallic components

In order to take advantage of the specific structural and functional properties inside a multi‐material assembly, it is necessary to provide adapted joining technologies. Therefore, the new joining technology “thermoclinching” was developed to join endless fiber reinforced thermoplastic composites and metallic joining partners. Previous experimental and numerical studies demonstrated the potential of the novel joining technology. In experimental and numerical studies essential geometrical and material parameters influencing the forming behavior are identified and evaluated. Thereby, the inline‐thermoclinching technology is developed by integrating the pre‐processed steps of cutting and heating into the actual joining process. For structural analysis of the joining zone as well as for quality analysis and validation of the process simulations computer tomography (CT) is used. Furthermore, experimental characterizations of the failure behavior of thermoclinched joints and the development of simulation models as well as strategies for numerical strength analyses are carried out.     

Temperature-induced strain mediated magnetization changes in NiFe2O4/BaTiO3 heterostructure

Herein, we report the temperature-induced magnetization changes of NiFe₂O₄ thin film, which is coated over a ferroelectric BaTiO₃ ceramic substrate. The solid-state reaction method was adopted for the preparation of ferroelectric BaTiO₃ (BT) substrate, whereas NiFe₂O₄ (NFO) film was deposited by spin-coating method. Rietveld refinement revealed that BT substrate has a tetragonal (P4mm) crystal system along with a minor orthorhombic phase (Amm2) at room temperature. The GIXRD analysis confirms the phase purity of NFO/BT heterostructure. Polarization hysteresis with respect to electric field (P-E loop) and the temperature-dependent dielectric measurement of BT substrate demonstrate its typical ferroelectric and phase transition behavior, respectively. Magnetization hysteresis loops were recorded for the NFO/BT heterostructure at 150, 240 and 300?K. A significant increase in the remnant magnetization (M_R) and coercive field (H_C) of NFO film are noticed while cooling the heterostructure below 300?K. Variation in the magnetization of NFO film corresponds to the change in the structural phase transition (Amm2 at 240?K and R3c at 150?K) of BT while cooling below RT. The interfacial strain mediated coupling is the primary mechanism attributed to the temperature-induced changes in the magnetization of NFO/BT heterostructure.     

Synthesis and Biological Evaluation of (−) and (+)-Spiroleucettadine and Analogues

A second-generation enantiospecific synthesis of spiroleucettadine is described. The original reported antibacterial activity was not observed when the experiment was repeated on the synthetic samples; however, significant anti-proliferative activity was uncovered for both enantiomers of spiroleucettadine. Comparison of the optical rotational data and ORD-CD spectra of both enantiomers and the reported spectrum from the natural source have not provided a definitive answer regarding the absolute stereochemistry of naturally occurring spiroleucettadine. Efforts then focussed on alteration at the C-4 and C-5 positions of the slightly more active (−)-spiroleucettadine. Ten analogues were synthesised, with three analogues found to possess similar anti-proliferative profiles to spiroleucettadine against the H522 lung cancer cell line.     

Removal of hexavalent chromium from wastewater using a new composite chitosan biosorbent

A new composite chitosan biosorbent was prepared by coating chitosan, a glucosamine biopolymer, onto ceramic alumina. The composite bioadsorbent was characterized by high-temperature pyrolysis, porosimetry, scanning electron microscopy, and X-ray photoelectron spectroscopy. Batch isothermal equilibrium and continuous column adsorption experiments were conducted at 25 degrees C to evaluate the biosorbent for the removal of hexavalent chromium from synthetic as well as field samples obtained from chrome plating facilities. The effect of pH, sulfate, and chloride ion on adsorption was also investigated. The biosorbent loaded with Cr(VI) was regenerated using 0.1 M sodium hydroxide solution. A comparison of the results of the present investigation with those reported in the literature showed that chitosan coated on alumina exhibits greater adsorption capacity for chromium(VI). Further, experimental equilibrium data were fitted to Langmuir and Freundlich adsorption isotherms, and values of the parameters of the isotherms are reported. The ultimate capacity obtained from the Langmuir model is 153.85 mg/g chitosan.     

Determination of strain rate dependent through-thickness tensile properties of textile reinforced thermoplastic composites using L-shaped beam specimens

The presented work focuses on a methodology to characterise strain rate dependent strength and elastic properties of textile reinforced composites in laminate through-thickness direction. Here, for the characterisation L-shaped beam specimens are used. The investigated composite is a fabric reinforced thermoplast made of hybrid E-glass/polypropylene yarns. The analytical solution for the determination of the through-thickness tensile strength as proposed by Lekhnitskii and Shivakumar is verified by means of an optical deformation analysis and is extended for thew determination of the through-thickness elastic modulus. Finally, the possibility of the strain rate dependent characterisation is investigated and a Johnson-Cook based modelling approach is used to represent the apparent strain rate dependency of the through-thickness failure onset. The methodology is successfully used to capture the material strain rate effects with the according strength values and model parameters over a strain rate range of 10 ⁻⁴ s⁻¹ to 10 s⁻¹ as well as the elastic modulus.     

Thermal response and recyclability of poly(stearylacrylate-<Emphasis Type="Italic">co</Emphasis>-ethylene glycol dimethacrylate) gel as a VOCs absorbent

The development of absorbent materials for volatile organic compounds (VOCs) is in demand for a variety of environmental applications including protective barriers for VOCs point sources. One of the challenges for the currently available VOCs absorbents is their recyclability. In this study, we synthesized poly(stearylacrylate-co-ethylene glycol dimethacrylate) (NG-18) gels, and after rigorous characterization, investigated the absorption properties for VOCs. The synthesized gel could be recycled by immersing in ether and other chlorinated, aromatic, and aliphatic solvents and by cooling them at 0 °C. These recycling processes resulted in approximately 25% weight loss compared to the fully swollen state, due to the crystallization of long-alkyl chain component of the gel. This property shows the possibility of recycling absorbed solvents easily and its usefulness as VOCs absorbent material.     

Dehydration of 1,4-dioxane by pervaporation using crosslinked calcium alginate-chitosan blend membranes

Summary  Sodium alginate (SA) and chitosan (CS) blended membranes were crosslinked with maleic anhydride (MA) for the separation of 1,4-dioxane/water mixtures at 30 °C by pervaporation (PV). The membranes were characterized by Fourier transform infrared (FTIR) analysis and Ion Exchange Capacity (IEC) to verify the crosslinking. Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) pattern were used to observe the thermal degradation and crystalline nature of the membrane respectively. The membrane performance was studied by calculating flux, selectivity, and pervaporation separation index. Sorption studies were carried out to evaluate the extent of interaction and degree of swelling of the membranes in pure liquids as well as in binary mixtures. The effects of experimental parameters such as feed composition, membrane thickness, and permeate pressure on separation performance of the crosslinked membranes were determined. The experimental result suggested that the membrane has a good potential for breaking the aqueous azeotrope 1,4-dioxane.     

Antibiofilm and quorum sensing inhibitory potential of Cuminum cyminum and its secondary metabolite methyl eugenol against Gram negative bacterial pathogens

Quorum sensing inhibitory (QSI) activity of common South Indian spices and vegetables were evaluated using the bacterial model Chromobacterium violaceum. Among the 22 samples tested the QSI compound present in the methanolic extract of Cuminum cyminum at 2 mg/ml inhibited violacein production in C. violaceum. Further, the outcome of the present investigation reveals that C. cyminum extract strongly interferes with acyl homoserine lactone (AHL) regulated physiological functions coupled with biofilm formation such as flagellar motility and exopolysaccharides (EPS) production. It promotes the loosening of biofilm architecture and powerfully inhibits in vitro biofilm formation in Pseudomonas aeruginosa PAO1, Proteus mirabilis and Serratia marcescens at sub-MIC levels. The result of molecular docking analysis attributes the QSI activity exhibited by C. cyminum to methyl eugenol (ME). The ability of ME to interfere with quorum sensing (QS) systems of various Gram-negative bacterial pathogens comprising diverse AHL molecules was also assessed and ME was found to reduce the AHL dependent production of violacein, bioluminescence and biofilm formation.     

Investigation on the corrosion resistance of bagasse-rice husk-wood ash blended cement concrete by impressed voltage

In this study, the compressive strength, the durability to chloride penetration and the corrosion of concrete containing bagasse-rice husk-wood ash (BRWA) were tested. Normal strength concrete with water to binder ratio (w/b) of 0.45 and 0.60 were used. The Portland cement was partially replaced with BRWA at the dosage of 10% and 20% by weight of binder. For concrete with w/b of 0.60, the replacement level of 40% was also tested. The chloride penetration resistance of the concretes was evaluated using the measurement of non-steady state chloride diffusion coefficient by accelerated salt ponding. The accelerated corrosion test by impressed voltage (ACTIV) was also performed to verify the findings and to investigate the characteristics of corrosion in terms of the initial current, the time of initial crack, and the weight loss of embedded steel.From the experiment, it was found that the concrete with 20% BRWA had the highest gain of compressive strength at the ages ranging from 7 to 180 days. The results of the experiments of accelerated salt ponding were in good agreement and conformed with ACTIV. The increase of the incorporation of the BRWA reduced the chloride penetration. The diffusion coefficient was reduced by 30–40% and 65–70% for concrete containing 10% BRWA and 20% BRWA compared to control concrete. The results of ACTIV also indicated that the initial current and the weight loss of embedded steel reduced and the time of initial crack increased with the increase in the replacement level of BRWA.