Abstract: In this research, the effects of boron nitride (BN) and polybutadiene (BR) on thermal and mechanical properties of polylactic acid (PLA) composite films were studied. PLA thin film in the thickness of less than 0.2 mm was fabricated using the solvent casting method. The loadings of BN and BR of 0-7 wt% were applied to the PLA matrix. The morphologies of composite films were characterized by scanning electron microscopy (SEM). The thermal and mechanical properties were also investigated. It was found that the addition of BN and BR can improve the thermal properties of PLA composite films. PLA/BN3%/BR5% ternary composite films provided the higher thermal properties, tensile strength and Young’s modulus, compared to PLA/BN1%/BR5% ternary composite films.
Abstract: In this work, the improvement of thermal and ablative properties of the phenolic resin by the addition of silicon carbide (SiC) and montmorillonite (MMT) were studied. The phenolic composites were fabricated by hot compression. The thermal stabilities, mechanical properties and ablative properties of the neat phenolic resin and the SiC/MMT phenolic composites were examined using a Lloyd universal testing machine, thermogravimetric analysis (TGA) and ablation tests (an oxyacetylene torch), respectively. Mass ablation rates were measured after flame exposure. The results showed that SiC/MMT provided the higher thermal stabilities and lower ablation rates to the phenolic resin.
Abstract: The ignition and combustion characteristics of the fibre-reinforced phenolic composite were studied experimentally employing cone calorimeter. Various parameters, including the ignition time, the mass loss and mass loss rate (MLR), the heat release rate (HRR) and the concentration of the carbon dioxide and carbon monoxide were measured and presented. Linear correlations of the transformed ignition time (1/tig)0.55 and 1/tig, the first and second peak MLR, the average MLR and the peak HRR with the heat flux were demonstrated. Based upon the correlations and theoretical analyses, flammability properties including the critical heat flux (CHF) and the minimum heat flux, the ignition temperature, the heat of gasification and the heat of combustion were calculated. The specimen with the thickness of 3 mm was prone to be thermally thin material. The peak concentration of the carbon dioxide increased with the heat flux. However, the peak concentration of the carbon monoxide declined with an increase in the applied heat flux.
Abstract: This research aims to study the effect of the functionalization of the multiwall carbon nanotubes (MWCNTs) on the mechanical property improvement of phenolic composites for bipolar plate applications in proton exchange membrane fuel cells (PEMFC). The MWCNTs were oxidized by strong acid and silanized by silane coupling agent in order to enhance the interfacial adhesion between the MWCNTs and matrix and were used as reinforcement in the phenolic composites. The silanized MWCNTs was found to improve the mechanical properties of the composites; however, they caused the decrease of electrical conductivity due to the wrapping of the MWCNTs with non-conductive silane molecules. Nevertheless, the conductivity of more than 100 S/cm is maintained to meet the DOE requirement of materials for use as bipolar plates.
Abstract: The hydrophobicity of starch/PVA blend was improved by crosslinking with boric acid. It was found that the swelling ratio of the boric acid modified starch/PVA matrix decreased as function of boric acid concentration. FTIR spectra and SEM images demonstrated that the urea had been encapsulated in polymer matrix successfully. The urea release characteristic was explained with respect to the swelling ratio and crosslinking density of polymer matrix. In addition, the matrix displayed a good barrier for controlling the release rate of urea from pellet.
Abstract: Waste ceramic powder originating from the contemporary hollow bricks production is studied as a supplementary cementitious material in mortar composition. For the ceramic powder and cement, the measurement of chemical composition is done using XRF analysis. XRD device is used for the amorphous phase content measurement. The particle size distribution of ceramics and cement is accessed on a laser diffraction principle. Pozzolanic activity of ceramic powder was determined by the modified Chapelle test. The blended binder containing ceramic powder in an amount of 8, 16, and 24% of mass of cement is used for the preparation of mortars which are then characterized using the measurement of basic physical properties and mechanical properties. Among the basic physical properties, bulk density, matrix density and total open porosity are measured. The mechanical resistivity of mortars with blended binder is accessed by the compressive strength, flexural strength, and dynamic Young’s modulus measurement. Additionally, pore-size distribution of the developed mortars is analyzed using mercury intrusion porosimetry. Experimental data shows that an application of 24% waste ceramics in the blended binder provides sufficient mechanical resistivity of the mortar.
Abstract: The interior temperature and relative humidity are important parameters in order to achieve healthy, comfortable, sustainable, and energy efficient indoor environment. In this paper, cement-lime plaster with PCM addition is studied as a perspective material for moderation of indoor temperature and humidity fluctuations. Commercial dry plaster mixture is modified by PCM addition based on the water dispersion of polymer microencapsulated paraffinic wax. The dosage of PCM is 4, 8, and 12 mass% related to the dry mass of plaster mixture. For the developed plasters, basic physical, thermal and hygric properties are measured. Incorporation of PCM into the cement-lime matrix lead to the substantial increase of the heat storage capacity in dependence on temperature as well as to the improvement of moisture buffer value of the newly developed composites which brings efficient way to reduce daily moisture variations. The obtained data can find use in attaining the higher indoor climate stability with lower energy consumption and operational cost.
Abstract: The behaviour of reinforced concrete beam strengthened with Carbon Fiber Reinforced Polymer (CFRP) and Glass fiber reinforced polymer GFRP laminates was investigated using finite element models and the results are presented in this paper. The numerical investigation assessed the effect of the configuration of FRP strengthening laminates on the behaviour of concrete beams. The load-deflection behaviour, and ultimate load of strengthened beam were compared to those of un-strengthened concrete beams. It was shown that using U-shaped FRP sheets increased the ultimate load. The stiffness of the strengthed beam also increased after first yielding of steel reinforcing bars. At was also observed that strengthening beams with FRP laminates to one-fourth of the beam span, modifies the failure of the beam from shear-controlled near the end of the unstrengthened beam, to flexure-controlled near mid-span. CFRP produced better results compared GFRP in terms of the ability to enhance the behavior of strengthenened reinforced concrete beams.
Abstract: Steel Corrosion affects severely on the life and durability of RC structures. In order to investigate the relationship between partial corrosion of RC beams and its cracking morphology and flexural capacity, based on experimental data, RC partial corrosion beam models are simulated using finite element software to model the flexural cracks and capacity of corroded RC beam under different corrosion rates. The results of compared analysis with experiment are presented: with the increase of the corrosion rate, the cracking region is almost consistent, the number of cracks reduces gradually, crack spacing becomes more unequal, bending stiffness and yield strength greatly reduce, ultimate flexural capacity and energy absorption capacity deteriorates, numerical simulation results are in good agreement with experiment.