Hybrid Short Glass Fibre Composites Reinforced with Silica Micro-particles

This work investigates epoxy composites reinforced by randomly oriented, short glass fibres and silica microparticles. A full-factorial experiment evaluates the effects of glass fibre mass fraction (15 and 20 wt%) and length (5 and 10 mm), and the mass fraction of silica microparticles (5 and 10 wt%) on the apparent density and porosity, as well as the compressive and tensile strength and modulus of the hybrid composites. Hybrid epoxy composites present significantly higher tensile strength (9%) and modulus (57%), as well as compressive strength (up to 15%) relative to pure epoxy.

Crystal - Rotator-I - Rotator-II Phase Transitions in the Mixtures of Alkanes

Using the combination of Flory–Huggins theory of isotropic mixing and Landau theory, we discuss the crystal – rotator-I – rotator-II phase transitions in the binary mixture of alkanes. The influence of concentration on the order parameters and the transition temperatures is discussed. Theoretical results show the first order character of both the rotator-I to crystal and rotator-II to rotator-I phase transitions in the mixture of alkanes. A good agreement between theoretical and experimental results are presented in this paper.

Effect of sewage sludge ash filler on mode I and mode II interlaminar fracture toughness of S-glass/epoxy composites

In this study, the influence of sewage sludge ash (SSA) waste particle contents on the mechanical properties and interlaminar fracture toughness for mode I and mode II delamination of S-glass fiber reinforced epoxy composites were investigated. Composite laminate specimens for tensile, flexural double-cantilever beam (DCB) and end-notched flexure (ENF) tests were prepared and tested according to ASTM standards with 5, 10, 15 and 20 wt% SSA filled S-glass/epoxy composites. Properties improvement reasons was explained based on optical and scanning electron microscopy. The highest improvement in tensile and flexural strength was obtained with 10 wt% content of SSA. The highest mode I and mode II interlaminar fracture toughness’s were obtained with 15 wt% content of SSA. The mode I and mode II interlaminar fracture toughness’s improved by 33 and 63.6%, respectively, compared to the composite without SSA.

Electroelastic biaxial compression of nanoplates considering piezoelectric effects

In the present theoretical work, it is assumed that a piezoelectric nanoplate is connected to the voltage meter which voltages have resulted from deformation of the plate due to in-plane compressive forces whether they are critical buckling loads or arbitrary forces. In order to derive governing equations, a simplified four-variable shear deformation plate theory has been employed using Hamilton’s principle and Von-Kármán assumptions. Modified couple stress theory has been applied to considering size-dependent effects in nano size. In order to compare the results, a validation has been done with the results of macroscopic. Results have been presented by changing some parameters, such as aspect ratio, various boundary conditions and length scale parameter influence on the produced voltage by the piezoelectric nanoplate. The most important outcomes show that an increase in length scale parameter leads to decreasing the produced voltage at constant in-plane arbitrary forces.

Preparation of defect free TFC FO membranes using robust and highly porous ceramic substrate

In this study, robust and defect-free thin film composite (TFC) forward osmosis (FO) membranes have been successfully fabricated using ceramic hollow fibers as the substrate. Polydopamine (PDA) coating under controlled conditions is effective to reduce the surface pores of the substrate and make the substrate smooth enough for the interfacial polymerization. The pure water permeability (A), solute permeability (B) and structural parameter (S) of the resultant FO membrane are 0.854 L·m-2h-1bar-1 (LMH/Bar) 0.186 L·m-2h-1 (LMH) and 1720 µm, respectively. The water flux and reverse draw solute flux are measured using NaCl and proprietary ferric sodium citrate (FeNaCA) draw solutions at low and high osmotic pressure ranges. With increasing the osmotic pressure, higher water flux is obtained but its increase is not directly proportional to the increase in the osmotic pressure. At the membrane surface, the effect of dilutive concentration polarization is much less serious for FeNaCA draw solutions. At an osmotic pressure of 89.6 bar, the developed TFC membrane generates water fluxes of 11.5 and 30.0 LMH using NaCl and synthesized FeNaCA draw solutions. The corresponding reverse draw solute flux is 7.0 g·m-2h-1 (gMH) for NaCl draw solution but it is not detectable for FeNaCA draw solution. This means that the developed TFC FO membranes are defect free and their surface pores are at molecular level. The performance of the developed TFC FO membranes are also demonstrated for the enrichment of BSA protein.

Morphological, electromagnetic and absorbing properties of pani/epoxy resin samples

This work deals with the study of radar absorbing materials (RAM) based on conductive samples obtained with polyaniline (PAni) (5-20 wt%) inserted in epoxy resin matrix. SEM analyses show that the PAni presents granular morphology, with an average diameter of 5 µm, with structures evenly distributed. DRX and FT-IR analyses show that the PAni polymer was successfully obtained in its conductive form. Electrical permittivity and magnetic permeability measurements of PAni/epoxy samples were performed in the frequency range of 8.2 to 12.4 GHz (X-band). Microwave attenuation values showed that the PAni-20wt%/epoxy resin sample presented a maximum attenuation of -24 dB, i.e. ~99.6% attenuation of the incident radiation. It was also observed that the amount of attenuated energy varies according to the incident frequency and the specimen thickness.

Application of vegetable oil-based biopolyols in manufacturing of rigid polyurethane foams – short review

The development of polyurethane foams’ market, as well as ongoing trends associated with sustainable development cause increasingly growing interest in the utilization of materials from renewable resources. Great example of such phenomenon is the use of vegetable oils in manufacturing of foamed polyurethanes. These materials can be applied directly or after previous modifications in production of biopolyols, main constituents of polyurethanes. In this paper, analysis of polyurethane foams’ market was presented and forecasts pointing to the potentially increasing position of so-called bio-polyurethanes in the future. Moreover, this paper summarizes previously published reports related to the manufacturing of vegetable oil-based biopolyols and their further incorporation into formulations of rigid polyurethane foams.

The displacement view of a multilayered HSDT plate

This paper presents the state of displacement of a multilayered composite laminate subjected to transverse static load with varying balance, symmetric and anti-symmetric angle-ply and cross-ply staking sequences. Higher-order shear deformation theory (HSDT) is considered in the finite element formulation of nine-noded isoparametric element with seven degrees of freedom at each node. The finite element formulation is transformed into computer codes. A convergence study is carried out first to obtain the optimal mesh size for minimizing the computational time. The maximum deflection at the center of plate for both fixed and simply supported edges is verified with reported literature and a good conformity is found. An attempt has been made to observe the minimum value of maximum deflection in the laminate for attaining the maximum strength of laminate with a suitable combination of stacking sequences with a constant volume of material.

Reaction Mechanism and kinetics of In-Situ Polymerization of Pyrrole onto Textiles: A Review

Research of electro-conductive textiles based on conductive polymers like polypyrrole, has increased in the recent years due to their high potential applications in various field. Conductive polymers behave like insulator in their neutral states with typical electrical conductivity in the range 10-10 to 10-25 Scm-1. These neutral polymers can be converted into semi-conductive or conductive states with conductivities range of 1 Scm-1 to 10-4 Scm-1 through chemical or electro-chemical redox reactions. By the applications of these polymers onto a textile surface, we can be able to obtain novel composites which are strong, flexible, light weight and highly electro-conductive. These textile composites are suitable for applications such as heating pads, sensors, corrosion-protecting materials, actuators, electrochromic devices, EMI shielding etc. The methods of applications of conductive polymers onto the textile surface such as in-situ chemical, in-situ electro-chemical, in-situ vapor phase, in-situ polymerization in a supercritical fluid, solution coating process are described here briefly. Merits and demerits of these methods are mentioned here. Reaction mechanisms of chemical and electro-chemical polymerization proposed by the different researcher are described. Different factors affecting the kinetics of chemical and electro-chemical polymerization are accounted. Influence of textile materials on the kinetics of chemical polymerization is reviewed and reported.

Ti-Mo alloys: corrosion study in solutions simulating commercial gels

Regarding to the influence of chloride and fluoride ions on the corrosion resistance, the electrochemical behavior of Ti alloys has been deeply studied. In this work, the main goal was to investigate the electrochemical behavior of cp-Ti and Ti-Mo alloys containing 6, 10 and 15 wt% of Mo concentrations. All the samples were immersed in different solutions, such as 0.15 mol L-1 Na2SO4, 0.15 mol L-1 Ringer, 0.15 mol L-1 Ringer plus 0.036 mol L-1 NaF and 0.036 mol L-1 NaF. Simulating the commercial fluorinated gels, the NaF solutions naturally-aerated were prepared with 1450 ppm of fluoride ions. The electrochemical techniques applied in this work were the open-circuit potential, cyclic voltammetry, besides the technique for chemical identification, which was X-ray photoelectron spectroscopy. The formation and growth of TiO2 and MoO2 were identified, without pitting corrosion. The electrochemical stability and the corrosion resistance of the Ti-Mo alloys decreased in the solutions containing chloride and fluoride ions, with an appreciative decrease especially in the fluorinated medium. The Ti-Mo alloy with higher Mo content concentration was the material with higher corrosion resistance. Therefore, it is a promising candidate as a biomaterial, once the osseointegration needs a satisfactory corrosion resistance for being achieved.