Advanced Materials Research Vol. 548

Abstract: In order to compensate the dispersion in 40Gb/s optical links, the optical dispersion compensation is discussed because of its high compensation speed and small nonlinear. An optical equalizer, in post compensation, is presented and the results based on simulations show that an equalizer consisting of chirped fiber grating can mitigate dispersion effectively by setting the incident power from 6 to 8dBm.

Abstract: When fiber-reinforced composites (FRC) are subjected to compressive load parallel to the fiber direction, they fail as a result of fiber buckling and/or transverse failure of the resin. Compressive loading brings about two buckling modes to fibers. The first mode is shear buckling, and the other is transverse buckling. Recent studies support the hypothesis that fiber buckling causes compressive rupture. In this study, finite element modeling software was employed to examine the behavior of a resin-embedded single fiber in terms of fiber content ratio. The performed modeling procedures illustrated that the single fiber experiences three discrete failure modes depending on fiber content ratio; and then a corrected equation was proposed for each mode. Fiber content ratio of the composite is one of effective parameters to determine the compressive strength value. Optimum fiber content ratio has been measured using finite element method. Numerical results are compared to experimental ones to analyze the obtained results. The optimum fiber content ratio calculated by the finite element modeling was measured 40% in this paper.

Abstract: Silica-based porous bioactive ceramics was prepared by gel-casting method using silica xerogel powder. Xerogel was derived from rice husk ash. 42 vol.% solid containing slurry was prepared in 1:30 (MBAM:AM) monomer cross-linker solution. The srurry was thixotropic. Gel-casted body was machined efficiently. Dired cast body was sintered at 1100oC. Apatite layer was formed on silica body during In vitro bioactivity experiment. The results suggest that the gel-casted silica ceramics can be used as a bioceramics.

Abstract: Finite Element Method (FEM) has becoming more influences in analyzing and solving metal forming problems from the beginning of punch and die designed up to setting the appropriated surrounding constrains in the deformation processes. This research was concerning about the study of simulation in cold forward bar extrusion of some aluminum alloys reinforced with ceramic particles using a commercial FE program; MSC. Marc to enhance the analysis. Two most important parameters in extrusion were investigated, which included area reduction ratio, εA, and die angle, 2∂, that affected to the forming force in the workpiece. In this research, the matrix part of composites studied was varied as follow: AA6061, AA6082 and AA230A reinforced by particles of SiC and Al₂O₃. Also, the volume fraction of reinforcement was another material parameter needed for the study. The dimension of initial billet in the simulation had 24.7 mm of diameter and 30 mm of length. The punch and die were assumed to be rigid which neglected the deformation. In case of heat dissipation, they were not considered in this simulation; therefore, the process assumed to be done isothermally at room temperature of 20°C. From the modeling results, the suitable conditions for different parameters were obtained, which assisted to the consideration of appropriated forward bar extrusion processes of such particulate reinforced Metal Matrix Composites (MMCs).

Abstract: In this study, the flame-retardant PAN fiber with good moisture absorption, good mechanical properties and better thermal properties has been prepared by blending solution of sodium hydroxide and hydrazine hydrate. FTIR spectra presented that new amide and cyclization-crosslinked pyridine group band peaks appeared. X-ray diffraction showed that the the crystal structure of PAN fibers has been converted from quasicrystalline structure into partially crystallized structure after modification treatment. SEM micrographs indicated that the original longitudinal surface microgroove has changed to layered structure by surfical etchant.

Abstract: The surface of kevlar fiber was modified by phosphoric acid solutions (H₃PO₄) in this article. The structure and morphology of the modified fiber were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). The results showed that some polar groups were introduced into the molecular structure of aramid fibers. The interfacial properties of aramid fiber/epoxy composites were investigated by the single fiber pull-out test (SFP). The results showed that the interfacial shear strength (IFSS) of aramid/epoxy composites was remarkbly improved after surface modification and the breaking strength has not been affected appreciably. It provided an efficient method to make the surface modified Kevlar fiber for the application for the advanced composites at a lower production cost.

Abstract: In this work an attempt was made to reuse wooden waste for producing lightweight mortars by replacing natural sand. In fact, manufacturers of wooden product and furniture generate sawdust and offcuts. These are produced by cutting, drilling and milling operations where wood is removed from a finished product; they are often collected in filter bags or dust collectors. Three different percentages of substitution have been tried: 2.5%, 5% and 10% by volume of sand. Wooden waste was always pre-soaked in water and sometimes in calcium hydroxide aqueous solution in order to obtain wood mineralization before adding it to the mortar mixture. Mortars containing wooden waste were characterized by means of compression and bending tests, free drying shrinkage and thermal conductivity measurements.

Abstract: This paper aims at investigating the influence of curing process on kaolin-based geopolymers. Kaolin-based geopolymers were prepared by the alkali-activation of kaolin with alkali activating solution (mixture of NaOH and Na₂SiO₃ solutions). The compressive testing, XRD and FTIR analysis were performed. The compressive strength results showed that curing at 60°C for 3 day achieves better strength. XRD analysis revealed that the entire geopolymer sample reduced in intensities and became amorphous at longer age while FTIR analysis indicated the presence of geopolymer bondings. Both analyses showed the presence of large amount of un-reacted remained in the system were the reason of the low compressive strength obtained.

Abstract: This paper describes the synthesis of calcined kaolin geopolymeric powder from the alkaline activation of calcined kaolin followed by solidification and pulverizing process. The geopolymeric powder was used by just adding water to produce resulted geopolymer paste. In this paper, the effect of water-to-geopolymeric powder ratios on the properties of the resulted geopolymer paste was studied. This water-to-geopolymer powder ratio was similar to that of water-to-cement ratio in the case of ordinary Portland cement (OPC). However, the concept used here was based on geopolymerization process. The compressive strength, setting time and SEM analysis of the resulted geopolymer pastes were conducted. Highest strength was achieved at water-to-geopolymer powder ratio of 0.22. The resulted geopolymer paste could be handled up to 120 minutes and reached final setting after about 4 hours of setting. Microstructure showed the formation of geopolymeric gel after the addition of water to the geopolymeric powder.