Volume 22, Issue 1

In this work, organobentonite/sodium polyacrylate (OBT/PAAS) humidity-control composite material was prepared using intercalation polymerization. The humidity-control performance of this composite material was tested by desiccator method. Its morphology and structure were investigated by X-ray diffraction and environmental scanning electronic microscopy. The results showed that the nanoscale layers of bentonite (BT) were dispersed in the polymer matrix of the prepared OBT/PAAS. OBT/PAAS has great moisture adsorption ability under high relative humidity (RH). The moisture adsorption ability of OBT/PAAS is greater than its moisture release ability, and its moisture adsorption rate is greater than its moisture release rate. The moisture adsorption capacities of BT, OBT, and OBT/PAAS at 97.42%RH are 0.12, 0.20, and 0.87 g/g, respectively.

The aim of this work was to prepare and characterize nanocomposites containing graphene from intercalated graphite. The graphene was produced by rapid thermal expansion using expandable graphite oxide or obtained commercially. The polymer used was poly(styrene- b -butadiene- b -styrene) (SBS). The SBS was dissolved in p -xylene and the graphene was ultrasonically suspended in the xylene solution. The morphology, dynamic mechanical, electrical, and thermal properties of composites were characterized. Graphene at 1% (w/w) (hydrogen atmosphere) was found to increase the storage modulus (68%) and loss modulus (147%) of the glassy state of polybutadiene in SBS. The damping factor of SBS was enhanced by 74% corresponding to the polystyrene phase of SBS using Cheap Tubes graphene. The composites were insulators at 1% (w/w). The styrene groups in SBS strongly adsorb onto the graphenes, preventing a percolation network that would enhance electrical permittivity. Graphene enhanced physical crosslinks of the polystyrene phase to increase the modulus at low concentration. Graphene dispersion using ultrasonic shear depended on π-π interactions between the aromatic rings of the solvent, graphene, and polystyrene. This is a simple, fast, cheap, and scalable way of making high-quality graphene and a new way of graphene dispersal in polymers.

A series of long glass fiber (LGF)-reinforced epoxy resin (ER), thermoplastic polyurethane (TPU) elastomers, and poly(methyl methacrylate) (PMMA) composites were prepared by using self-designed impregnation device. Dynamic mechanical properties of the LGF/ER/TPU/PMMA composites have been investigated by using dynamic mechanical thermal analysis (DMA). The results indicated that the content of PMMA and TPU and scanning frequency had important influence on dynamic mechanical properties and glass transition of the LGF/ER/TPU/PMMA composites. In addition, the Arrhenius relationship has been used to calculate the activation energy of α-transition of the LGF/ER/TPU/PMMA composites. The thermal properties of the LGF/ER/TPU/PMMA composites were studied by thermogravimetric analysis (TGA). Morphology and mechanical properties of the composites are investigated by scanning electron microscopy (SEM), a universal testing machine, and a ZBC-4 Impact Pendulum.

To our knowledge, here is the first time that Stellite SF12-Si 3 N 4 -B 4 C-Ce 2 O 3 powders are deposited on a TA1 titanium alloy as the composites by a laser melted deposition (LMD) technique. It is noted that compared with a TA1 alloy substrate, an improvement of cyclic oxidation resistance is obtained for such LMD composites. Scanning electron microscopy results indicate that many nanocrystalline/amorphous phases are produced, which improve the oxidation resistance of such composites. Such composites exhibit better oxidation resistance than the composites without Ce 2 O 3 due to the formation of denser and finer-grain scale. The effect of Ce 2 O 3 on the formation mechanism and oxidation behavior of such composites is discussed in detail.

The distribution of stresses in laminated composite plates with a central circular hole and having various stacking sequences, different geometric dimensions and subjected to in-plane axial tensile loading was investigated. The ANSYS computer program was utilized using the finite element method to study the linear and nonlinear material effects. A new method was proposed for the purpose of incorporating the material nonlinearity model into the ANSYS computer program using the secant modulus material model. The aim of the authors is to analyze the effect of D / b and a / b ratios (where D is hole diameter, b is plate width, and a is plate length) on stresses induced in such plates. Analysis was carried out for angle-ply, four-layered symmetric laminated rectangular plates with various stacking sequences [± θ ] s .

The vibration behavior of functionally graded carbon nanotube (CNT)-reinforced composite (FG-CNTRC) plates under a moving load is investigated based on the first-order shear deformation theory of plates using the finite element method. An embedded single-walled CNT (SWCNT) in the polymer matrix and its surrounding interphase is replaced with an equivalent fiber to obtain the effective mechanical properties of the CNT/polymer composite plates using the Eshelby-Mori-Tanaka micromechanical model. The equations of motion of plate elements are derived by utilizing Hamilton’s principle. Newmark’s time integration scheme is employed to discretize the equations of motion in the temporal domain. The convergence of the method is numerically demonstrated and its accuracy is shown by performing comparison studies with existing solutions for the free vibration and static analysis of FG-CNTRC plates and also the exact solution of isotropic plates under a moving load. Then, the numerical results are presented to study the effects of various profiles of the CNT distribution, which includes both symmetric and asymmetric distributions, the velocity of the moving load, and thickness-to-length and aspect ratios together with boundary conditions on the dynamic characteristic of the FG-CNTRC plate under a moving load.

The free vibration analysis of generally laminated composite beam (LCB) with a delamination is presented using the finite element method (FEM). The effect of material couplings (bending-tension, bending-twist, and tension-twist couplings) with the effects of shear deformation, rotary inertia, and Poisson’s effect are taken into account. To verify the validity and the accuracy of this study, the numerical solutions are presented and compared with the results from available references and very good agreement observed. Furthermore, the effects of some parameters such as slenderness ratio, the rotary inertia, the shear deformation, material anisotropy, ply configuration, and delamination parameters on the natural frequency of the delaminated beam are examined.

The ultrafine grain structure is very difficult to fabricate by severe plastic deformation (SPD) for metals with poor formability. In this paper, a fabrication technology of ultrafine structured dissimilar laminated metal composite sheets (LMCS) was developed for poor plastic metals which have low elongation by hot accumulative roll bonding (ARB) in conjunction with cold rolling. The hot ARBed 1100/7075 LMCS was cold rolled at room temperature after recrystallization annealing treatment. An ultrafine structured dissimilar LMCS was obtained without undergoing severe cold rolled deformation. The mechanical properties were enhanced and optimized by using heat treatment technology. The accelerated refining mechanism of grain was revealed by microstructure characterization of the composite sheet. The enhanced strength was mainly derived from the fine layers, refined grains, increased dislocation accumulation, and abundant dispersoids. The results of the research are helpful in improving the mechanical properties of dissimilar LMCS and optimizing the preparation technology.

In the present work, an attempt has been made to investigate the drilling behavior of the titanium dioxide (TiO 2 )- and zinc sulfide (ZnS)-filled glass fabric-reinforced polymer (GFRP) matrix composites. The volume fractions in the matrix were chosen as 1%, 2%, and 3%. Drilling has been conducted on CNC Vertical Machining Center. Speed and feed of drilling and drill tool geometry were considered as the varying parameters with three levels. Thrust force, delamination factor, and surface roughness have been considered as the output parameters and measured in each combination of parameters chosen. Results reveal that the addition of filler will increase the thrust force developed during drilling and indicate that drill point angle has a direct effect on the thrust value. Delamination factor increases with increase in feed and decreases as speed increases. Also, it can be observed that surface roughness decreases with increase in speed and increases with increase in feed. ZnS-filled composite shows less damage than TiO 2 .

Carbon fiber-reinforced plastic (CFRP) composites are materials that are difficult to machine due to the anisotropic and heterogeneous properties of the material and poor surface quality, which can be seen during the machining process. The machining of these materials causes delamination and surface roughness owing to excessive cutting forces. This causes the material not to be used. The reduction of damage and surface roughness is an important aspect for product quality. Therefore, the experimental study carried out on milling of CFRP composite material is of great importance. End milling tests were performed at CNC milling vertical machining center. In the experiments, parameters considered for the end milling of CFRP were cutting speed, feed rate, and flute number of end mill. The results showed that damage, surface roughness, and cutting forces were affected by cutting parameters and flute number of end mill. The best machining conditions were achieved at low feed rate and four-flute end mill.

This study presents the application of soft computing techniques, namely, as multiple regressions (MRs), neural networks (NNs), genetic programming (GP), and adaptive neuro-fuzzy inference system (ANFIS) for modeling of compressive strength of carbon fiber-reinforced polymer (CFRP) confined concrete cylinders. The proposed soft computing models are based on experimental results collected from literature. They represent the ultimate strength of concrete cylinders after confinement with CFRP composites, which is in terms of diameter and height of the cylindrical specimen, ultimate circumferential strain in the CFRP jacket, elastic modulus of CFRP, unconfined concrete strength, and total thickness of CFRP layer used. The accuracy of the proposed soft computing models is very satisfactory compared to experimental results. Moreover, the results of proposed soft computing models are compared with five models existing in the literature proposed by various researchers so far and are found to be, by far, more accurate.