Volume 19, Issue 4

Polypropylene composites containing layered silicate and glass fibers are prepared by melt compounding. To investigate the influence of the processing conditions on the mechanical properties and the morphology of short glass fiber-reinforced polypropylene-layered silicate composites, the process parameters are varied while preparing the composites. The processing conditions affect the mechanical properties and the morphology. The investigations suggest that a short glass fiber-reinforced polypropylene-layered silicate composite should be compounded at a maximum barrel temperature of 200°C, a throughput of 30 kg/h at a screw speed of 500 min -1 and a screw configuration, which introduces a large amount of shear energy into the composite. These processing conditions lead to a comparatively high specific mechanical energy input of 206 Wh/kg and to the best set of mechanical properties of the investigated materials. However, the morphology of the investigated short glass fiber-reinforced nanocomposites does not show significant differences and has to be investigated further.

A specific fiber-reinforced elastomer (FRE) composite was formed by inserting curved fibers into a rubber matrix. This material combined the hyperelastic behavior of a soft elastomer matrix with the high stiffness character of a fibrous reinforcement. A biphasic loading property could be realized physically. Based on the guided concept, experiments were performed on the specimens of pure and fiber-reinforced silicone rubber, respectively. Test results showed that this FRE composite first experienced an elastomer-dominant phase with a large recoverable deformation and then a fiber-dominant phase with rapid increasing loading. This biphasic behavior of the developed FRE composite was also identified by the constitutive equations based on the nonlinear solid mechanics. It was further discovered that the division of the two phases could be varied with the change of curved fiber length.

This paper reports the preparation of the amine/epoxy blends with various amines such as 4,4′-diaminodiphenylsulfone (DDS), one nitrile side chain-containing diamine (BDB), and phthalonitrile-containing amine (APN). Differential scanning calorimetry (DSC), rheological analysis, and thermal gravimetric analysis (TGA) were used to evaluate the curing behaviors and thermal properties of amine/epoxy blends with the effect of functional nitrile groups of amines. Interestingly, an amine/epoxy blend exhibited double curing reactions. The cured epoxy copolymers exhibited high glass transition temperatures (>220°C) and excellent thermal stabilities having 5% weight loss temperature in the range of 375°C to 383°C.

In this study, A356-SiC p metal-matrix composites were produced through thixomoulding process, and these composites were subjected to wear tests. The composites containing various volume fractions of SiC p particles (5%, 10%, 15% and 20%) as the reinforcement were produced at two different temperatures of 590°C and 600°C. The influences of processing temperatures and reinforcement ratio on the properties and wear behaviour of the composites were investigated. Prior to the wear tests, microstructural properties and hardness of the composites were determined. For the wear tests, a pin-on-disc-type wear apparatus was employed to carry out the wear tests. The wear tests were carried out at 2.0 m/s sliding speed under 15 N load and for four different sliding distances. A scanning electron microscope (SEM) was used to examine the wear mechanisms on the worn surfaces of the composites. The results indicated that sphericity rate and hardness of the composites produced at 590°C were higher than those of the composites produced at 600°C. In addition, the composites produced at 590°C exhibited lower weight loss and friction coefficient.

Fouling causes huge material and economic costs in maintenance of mariculture, shipping, naval vessels, and seawater pipelines, etc. Prevention of biofouling is an important property expected of coatings in these fields. In the present work, we prepared nano ZnO/acrylic latex by mechanical mixing as well as by the in situ method. The effect of nanoparticles on the drying of coatings and their antimicrobial nature were investigated.

This study deals with stress analysis of functionally graded discs subjected to internal pressure and various temperature distributions, such as uniform T , linearly increasing T o , and decreasing T i temperatures in radial directions. For analytical study, the closed-form solutions for stresses and displacements are obtained by using the infinitesimal deformation theory of elasticity. For graded parameters, power law functions are used in analytical and numerical solutions. For numerical study, discs are modeled and analyzed by using a commercial finite element program, ANSYS ® . Metal matrix composite, AlSiC, is selected as disc material. Results obtained both analytical and numerical solutions are found very well consistent with each other. The tangential stresses are found higher than the radial stresses at the inner surface for all thermal loads, and they vary from compressive to tensile and from tensile to compressive depending on the functionally graded material (FGM) properties and temperature loads. The radial stresses are found zero at the inner and outer surface and higher at one third of the disc section near the inner surface. They are also found as compressive and tensile stresses depending on the material properties and temperature loads.

In this study, we worked to estimate the fracture energy of steel fibre-reinforced concrete (SFRC) according to the water/cement ratio (w/c), tensile strength of steel fibre, steel fibre volume fraction and flexural strength of concrete sample as inputs using the Mamdani-type fuzzy inference system (FIS). In the study, the values obtained from the model and experimental divided three groups (each group has six experimental results) according to the w/c ratios to evaluate the fuzzy logic (FL) model approximate reasoning ability. As a result, the Mamdani-type FIS has shown a satisfying relation with the experimental results and suggests an alternative approach to evaluate the fracture energy estimation using related inputs.

This paper deals with frequency optimization of symmetrically laminated angle-ply spherical shells. The design objective is the maximization of the fundamental frequency, and the design variable is the fiber orientation in the layers. The first-order shear deformation theory and nine-node isoparametric finite element model are used for the finite element solution of the laminates. The modified feasible direction (MFD) method is used for the optimization routine. For this purpose, a program based on FORTRAN is used. Finally, the numerical analysis is carried out to investigate the effects of geometrical parameters and boundary conditions on the optimal designs, and the results are compared.

A hard composite coating was fabricated by laser alloying of the Co-Fe-Al+B 4 C-Si 3 N 4 mixed powders on TA15 (Ti-6Al-2Zr-1Mo-1V) titanium alloy in an open system. The composite coating mainly consisted of γ-Co, TiB 2 , TiB, TiC 0.3 N 0.7 , SiC, Ti 3 Al, FeAl, and Co-Ti intermetallics. The TEM diffraction pattern results indicated that the orientation relationship between TiB 2 and TiC 0.3 N 0.7 was (1 - 20)TiB 2 //(2 - 20)TiC 0.3 N 0.7 in such a coating. Furthermore, during the alloying process, a number of Mo and Zr entered into the molten pool from the substrate due to the dilution effect, which refined the microstructures of the composite coating and also increased the amorphous phase content.

Rheological, mechanical, and transport properties of high-performance self-compacting concrete (HPSCC) mixes with different cement contents and fly ash percentages are studied in this research. Different HPSCC mixtures were investigated with cement contents of 400, 450, and 500 kg/m 3 and fly ash percentages of 5%, 10%, and 15%. In order to achieve an enhanced durability, the aggregate grading curve was modified and improved based on power 0.45 grading curve. For a better understanding of fly ash effect and comparison purposes, a constant water to binder ratio (w/b=0.38) was used. The rheological properties were observed through slump flow time and diameter and V-funnel flow time. Mechanical properties including compressive and splitting tensile strength were determined at 7, 28, and 90 days. A comprehensive transport investigation was carried out using water absorption, capillary absorption, chloride ion percentage, and resistivity tests. The results showed a desirable improvement in rheological properties, and the compressive strength improved by about 10% for 15% fly ash at 90 days. A relatively significant improvement was also considered in all transport properties by increasing the fly ash percentage and cement content, especially at higher ages.

A parametric experimental study has been conducted to investigate the effect of polypropylene fiber on the workability and fracture properties of high-performance concrete (HPC) composites containing fly ash and silica fume, with the five fiber volume fractions (0.04%, 0.06%, 0.08%, 0.1%, and 0.12%) used. The results indicate that the addition of polypropylene fiber decreases the workability of the HPC composites containing fly ash and silica fume. With the increase in the fiber volume fraction, both of the slump and the slump flow decrease gradually. Furthermore, the addition of polypropylene fiber has greatly improved the fracture parameters of concrete composite containing 15% fly ash and 6% silica fume, such as fracture toughness, fracture energy, effective crack length, maximum midspan deflection, the critical crack opening displacement, and the maximum crack opening displacement of the three-point bending beam specimens. When the fiber volume fraction increases from 0% to 0.12%, the fracture parameters increase gradually. The variation rules of the fracture parameters indicate that the capability of the polypropylene fiber to resist the crack propagation of the concrete composite containing 15% fly ash and 6% silica fume is becoming stronger and stronger with the increase in fiber volume fraction with the fiber volume fraction not above 0.12%.

In this paper, transport properties of high-performance self-compacting concrete (SCC), as one of the important cementitious composites incorporating micro and nano silica (NS) (SiO 2 ) into the binder, have been investigated. For this purpose, different mixtures were designed with different amounts of silica fume (SF) and NS admixtures. Different binder contents were also investigated to observe the binder content effect on the concrete properties. Corrosion behavior was evaluated by chloride penetration and resistivity tests. Water absorption and capillary absorption were also measured as other durability related properties. The results showed that water absorption, capillary absorption, and Cl ion percentage decreased rather significantly in the mixtures containing admixtures especially the blend of SF and NS. By addition of the admixtures, resistivity of the SCC mixtures increased, which can lead to reduction of corrosion probability.

This article mainly aims at experiments to modify the matrix phase in glass fiber-reinforced plastics anchor (GFRP-anchor), trying to achieve the enhancement in the torsional performance of GFRP-anchor in order to expand its application field. The experiments were to add the mineral filling nano mullite powder and the toughening agent acrylic-polyurethane emulsion with different proportions into the matrix phase which experienced a vacuum-pumping process for the removal of bubble, while the same reinforced phase glass fiber was used by all the GFRP-anchor samples with the same forming process conditions. Torsion test and scanning electron microscopy (SEM) observations were investigated, and the results revealed that adding nano mullite powder into the matrix phase as the mineral filling with the mass fraction ratio of 1.5%, the acrylic polyurethane emulsion as the toughening agent with 5%, as well as the vacuum-pumping process for the removal of bubble from the matrix phase, can greatly improve the torsional strength of the GFRP-anchor by 35%, 41%, and 51%, respectively.