نشریه علوم و فناوری کامپوزیت
سال هفتم شماره 1 (پیاپی 23، بهار 1399)

Tube hydroforming process is an unconventional method to deform tubular components to the desired shape of die cavity by applying high pressure and axial feed displacement. Bi-layered tubing which consists of two different metallic layers (such as aluminum and copper) is recommended to use in complex working environments as it offers combined properties that single layer structure does not have. Using of this tubes are suggested in transferring high-temperature corrosive fluids, aerospace and aviation industries, oil production and nuclear power plants. In this paper, thickness reduction and wrinkle height of the bi-layered hydroformed tube are modeled in terms of geometrical factors (lengths, diameter and thickness of inner and outer tubes, lengths and heights of bulge, Chamfer lengths) using finite element method and design of experiments (DOE) with surface response method (RSM). As well, finite element model was built and experimentally validated. The geometrical factors effects and their interactions on the responses were determined and discussed. Optimum geometrical factors are obtained by minimizing thickness reduction and wrinkle height using multi-objective optimization. The optimization results are in good agreement with the experimental test.

Various methods are required for enhancing the strength of the composites, as a lightweight and optimized replacement for common materials such as metals. Addition of nano materials is a novel method for improving the strength of composite materials. On the other hand, the importance of impact phenomena and its many applications in various industries is obvious for everyone. Therefore, in this research, a multiscale composite of epoxy-basalt fibers containing nano silica and surface-modified nano graphene with a total weight percent of 1% was evaluated under high velocity impact test. Five series of composite samples containing 6 layers of basalt fibers made by hand layup method were impacted by two types of aluminum projectile in the speed of 116 m/s. Ogival and hemispherical head projectiles with the mass of 26.7 and 26.3 grams, respectively, were used. In order to investigate the surface modification process, Fourier transform infrared analysis (FT-IR) was performed and the effect of adding nano materials on the bond between the matrix and the fibers in the microscopic scale was investigated using the SEM microscope. The results showed that the sample containing 0.7% nano silica and 0.3% nano graphene had the best performance in absorbing the energy of the high velocity impact by increasing the absorption about 7.3% for a ogival projectile and 20.4% for a hemispherical projectile compared to a sample without nano materials.

The z-pins in spite of their small sizes and small weights, but they have been expanded to reduce the disadvantages of composites and sandwich panels, increase their resistances and strengths, and prevent crack growth. In this paper, using a finite element method, the behavior of multi-functional sandwich panels with z-pin cores in average strain rates (between 164-327 1/s) under Split Hopkinson pressure bar (SHPB) test have been investigated. The effects of strain rate and mechanical behavior of multifunctional sandwich panel subjected to dynamic loading were investigated and the results compared with the published experimental tests. Good agreements were found between them. Also, effective parameters such as embedding angle of z-pins, their materials and their diameters were investigated. In conclusion, the results show that the foresaid parameters have effective roles in increasing flow stress and ultimate strength of multifunctional sandwich panels. Furthermore, the mechanical properties of sandwich panel with z-pin and honeycomb were compared. The results show that in the same weight and Volume core condition, the ultimate strength and flexibility of z-pins are respectfully smaller and larger than honeycomb cores.

Due to wide application of conical sandwich shells in the advanced industries, it is nessesary to investigate the mechanical behavior of theses structures. In this paper, for the first time, by considering the flexibility of the core in the high order sandwich shells theory, the the vibration behavior of the truncated conical sandwich shells which include a porous FG core and two homogeneous face sheets are investigated in various thermal conditions. Temperature dependent materials are used in the core and the facesheets. The power law rule which modified by considering the two types of porosity volume fractions are applied to model the gradually variation of FGMs. By applying Hamilton's energy principle, considering the in-plane stresses in the core and the faces, and nonlinear von-karman strains for both mechanical and thermal stresses, the governing equations of motion are obtained. A Galerkin procedure are used to solve the equations in a simply supported boundary condition. Uniform, linear and nonlinear temperature distributions are used to model the effect of the temperature changing in the sandwich shell. To verify the results of these work, they are compared with FEM results obtained by Abaqus software and for special cases with the results in literature. Eigen frequencies variations are surveyed versus the temperature changing, geometrical effects, porosities, and some others in the numerical examples.

In this research, silica nanoparticles, graphite nanoparticles, and a mixture of silica and graphite nanoparticles were used to fabricate surface composites on AZ31B by the use of friction stir processing (FSP). The results after 4 passes indicated that, in comparison with as-received AZ31B, the mean grain size in the sir zone for AZ31B/SiO2, AZ31B/graphite, and AZ31B/SiO2/graphite decreased about 82%, 70%, and 80% respectively. Furthermore, in comparison with as-received AZ31B, microhardness increased 33%, 18.8%, and 20.6% respectively. Although graphite, as a solid lubricant, decreased hardness, the results of wear test indicated that wear rate of AZ31B/graphite and AZ31B/SiO2/graphite is almost similar to wear rate of AZ31B/SiO2. The investigation of TEM images indicated that the size of sub-grains for AZ31B/SiO2/graphite was 18% smaller than AZ31B/SiO2. Furthermore, the results of the corrosion test indicated that the corrosion current of AZ31B/SiO2 reduced over 89% compared with as-received AZ31B, and AZ31B/SiO2/graphite had the highest corrosion potential.

In this research, with the aim of improve the loading efficiency and particle size, Chitosan (CS)-Montmorillonite (MMT) nanocomposite were prepared using a ionic gelatinization method for controlled delivery of curcumin and optimized via response surface method. Different variables (Chitosan concentration, MMT percentage, surfactant concentration, drug amount and sonication time) were used to determine the optimum formulation. Two parameters of polysaccharide concentration and tween volume were selected to obtain optimum formulation with highest loading efficiency and minimum particle size. Polysaccharide concentration, surfactant concentration and sonication time had higher effect on particle size. MMT addition significantly enhanced the entrapment efficiency of Curcumin and the optimal value for MMT was 3 w%. Also, the increase in drug amount (mg/ml) resulted in the increase in entrapment efficiency. Physicochemical characteristics of optimal formulation were determined in terms of entrapment efficiency, release profile, Size, Zeta potential, surface morphology and FTIR spectra. Formulation A2 with 23.8-31.3 nm diameter size, 93.71% entrapment efficiency and -38.73 ± 0.88 mV Zeta potential was selected as the optimum formulation. SEM and FTIR studies revealed spherical morphology and lack of chemical interaction between nano system and drug.

In this study, the effect of vascular self-healing orientation on tensile strength and healing efficiency of epoxy-glass composite has been experimentally studied. Hollow glass fiber (HGF) of 450±10 μm diameter and 50%-55% hollowness was produced by using an extruder. Following, the HGFs were filled with healing components, and subsequently employed as vascular healing system in composite laminate. The orientations of HGFs were selected at three levels of 0, 45 and 90°. The distance of HGFs was kept at 200 μm. The virgin, damaged and healed specimens were characterized in term of tensile behavior and subsequently the healing efficiency was studied. The results of tensile tests indicated that the presence of blank HGFs in composite lowered the tensile strength as high as 17, 14 and 21% for HGFs angles of 0, 45 and 90°, respectively. As a damage, a strain of 1.2% was initiated in the tensile specimen and afterward the self-healing process was accomplished at temperature of 70 ˚C for a time period of 48 hours. Subsequently, the healing efficiency was measured by tensile testing. The results indicated that the best orientation of the filled HGFs was 45°, where the healing efficiency was equal to 42%. The morphology of fractured HGFs and healed zones was studied by employing scanning electron microscopy.

In the present investigation, the mode I fracture toughness of unidirectional E-glass/vinyl ester composites subjected to sulfuric acid was studied. Specimens were manufactured using the hand lay-up method with the [0]_18 stacking sequence according to standard size. Specimens were exposed to 20 wt.% sulfuric acid (with 98% purity) at the laboratory temperature for 0, 1, 2, 5 and 10 weeks. Subsequent to conditioning for the aforesaid period of times, samples were dried and according to the standard, the double cantilever beam tests were performed to study variations of the initiation and propagation fracture toughness. Results show a reduction in the propagation fracture toughness after conditioning, although the variation of the initiation fracture toughness at the first 5 weeks was increasingly and after that at the 10th week had a significant reduction. Moreover, it was observed that the amount of the crack initiation force of samples was decreased after the conditioning.

In this paper a new multi-scale method was presented to calculate the elastic modulus of graphene/polymer nano composites. Macro, micro and nano scales were considered within this hierarchical multi-scale method. In macro scale, a nanocomposite was modeled with a cubic representative volume element (RVE) which was constructed by several small cubic elements in micro scale. Each element in micro or nano scale, is made of aligned graphenes which were oriented in three dimensional space via a random algorithm. The stiffness tensor of each element was obtained by Mori-Tanaka micromechanical method and the elastic modulus of the RVE was calculated using a new analytical approach. In fact this method is a development of the laminated analogy, in to a three dimensional version which is in better accordance with the physics of real nanocomposites. It has been shown that the results of the present approach are in good agreement with several experimental works in the literature.

The purpose of this study is the improvement of the mechanical, thermal, and anti-bacterial properties of the Polylactic Acid (PLA)/Chitosan films by adding the Titanium Oxide nanoparticles. The titanium oxide nanoparticles in content of 1, 3, and 5 wt.% were added into PLA/Chitosan matrix. Tensile test for determining the tensile strength, elastic modulus and elongation, Differential Scanning Calorimetry test for evaluating the thermal properties of the samples, and anti-bacterial test for determining the anti-bacterial behavior of the polymer samples were done. The Scanning Electron microscopy (SEM) mages were taken to investigate the morphology and nanoparticles dispersion in the polymer matrix. The SEM images showed that the nanoparticles were dispersed in the matrix homogenously. The tensile test showed that the nanoparticles in content of 3 wt.% improved the tensile strength and elastic modulus significantly. DSC test showed that the addition of the titanium oxide nanoparticles into PLA/Chitosan increases the crystalline temperature and degree of crystallinity. The nanoparticles improved the anti-bacterial properties of the PLA/Chitosan matrix.

This paper experimentally investigated high velocity impact on basalt reinforced aluminum laminate with nanoclay. The FML plate is made of two Aluminum 2024 facing sheets and basalt/epoxy/nanoclay as nano composite core. Nano composite section has been composed of four basalt fibers 300 g/m2, resin EPR1080, hardener EA1080 and nanoclay Bentonite B0109 dispersed into the epoxy system in a 0%, 1%, 3% and 5% ratio in weight with respect to the matrix. All panels are fabricated using Hand Lay-up method. Ultrasonic device was also used for homogenization and better dispersion of nanoclay in epoxy matrix. Ballistic tests were conducted using Gas Gun at the velocity of 205, 220 and 235 m/s. The results of the ballistic impact experiments show that the addition of nanoclay particles to the structure of this type of FMLs significantly increases the ballistic velocity and energy absorption. Also, the optimum addition rate of these nanoparticles has been 3% of mass compared to the resin; so addition of this amount of nanoclay particles increases the average of ballistic limit velocity and absorbed energy by 6.85% and 14.1%, respectively.

In this research, first Zinc- Cobalt ferrite particles, with Co0.5Zn0.5Fe2O4 formula, was prepared via sol–gel auto-combustion method. The magnetic particles were characterized by WAXD and FT- IR techniques. WAXD analysis exhibited the diffraction peaks of the cubic spinel structure for the synthesized nanoparticles. Then, they were employed in the preparation of PANI/ Co0.5Zn0.5Fe2O4 composites, with 3:1, 1:1 and 1:6 weight ratios, by in situ polymerization of aniline monomer in the presence of proper amount of Co0.5Zn0.5Fe2O4 nano particles and ammonium persulfate as initiator. The synthesized composites were analyzed by FT-IR, SEM and XRD methods. Subsequently, polyaniline/Co0.5Zn0.5Fe2O4 particles were incorporated (in 20 wt. %) in an epoxy resin matrix to produce final nanocomposites. The morphological properties of these composites were investigated by TEM. Based on TEM image, particle sizes between 10-100 nm were found for polyaniline/Co0.5Zn0.5Fe2O4 nano powders. The reflection loss of fabricated nano composites was measured in the radar region, i.e. the frequency range of 8-12 GHz. In the proper amount of 1:1 weight ratio of polyaniline to Co0.5Zn0.5Fe2O4, reflection loss reached its minimum value of -16 dB

Fiber metal laminates (FMLs) are hybrid structures composed of composite lightweight layers and aluminum layers that have high impact resistance and energy absorption along with low weight. In this study, by using of governing equation of non-linear behavior of FMLs, the effect of various parameter such as temperature and dynamic loading have been investigated. For this purpose, the geometric nonlinearity effects are taken into account with the von Kármán large deflection theory and the governing equations of motion for the plate are derived by the use of the virtual work principle. The simply supported boundary conditions are considered for all edges of the plate. Then, Nonlinear Partial differential Equations (PDEs) of motion by using of the Galerkin method are transformed to a single nonlinear Ordinary Differential Equation (ODE), which is solved analytically by the multiple time scales method, and an analytical relation is found for the nonlinear frequency of these plates. The results of conducted theoretical analyses compared with the presented results in the literature and good agreement is found. By using the validated theoretical model, the influences of changes in temperature change, elastic foundation and peak pressure values are investigated. The results indicated that increasing the peak pressure values would lead to an increase in deformation and a decrease in the frequency ratio of the system. The results also show that FMLs would be a good choice for structures under dynamic loads.

This research presents, free vibration analysis of fiber metal-laminated (FML) plates on a total and partial elastic foundation using the generalized differential quadrature method (GDQM). The partial foundation consists of multi-section Winkler and Pasternak type elastic foundation. Taking into consideration the first-order shear deformation theory (FSDT), FML plate is modeled and its equations of motion and boundary conditions are derived using Hamilton’s principle. The formulations include Heaviside function effects due to the nonhomogeneous foundation. The novelty of this study is considering the effects of partial foundation and in-plane loading, in addition to considering the various boundary conditions of FML plate. A computer program is written using the present formulation for calculating the natural frequencies of composite plates without contact with elastic foundation and composite plates resting on partial foundations. The validation is done by comparison of continuous element model with available results in the literature. The results show that the constant of total or partial spring, elastic foundation parameter, thickness ratio, frequency mode number and boundary conditions play an important role on natural frequency of the FML plate resting on partial foundation under in-plane force.

Friction and wear in most engineering applications are undesirable phenomena, however in friction material composites, though wear is inevitable, friction is indispensable and reaching to a suitable and stable friction coefficient has been a major concern of many engineers. In this research, the surface wear of semi-metallic brake pad has been studied to assess the governing mechanism of friction surface. To get that point, the effect of steel fibers on the formation of primary and secondary contact plateaus as high lands through scanning electron microscopy (SEM) were investigated. In order to detect the friction layer of the composite, friction test was evaluated according to SAE J661 standard test procedure by a chase machine. The white light interferometer (WLI) was employed to reveal the surface roughness of the friction composite after braking. Output results showed that the presence of metal fibers as primary contact plateaus act as an anchor against abrasive particles and dust playing an effective role in forming the secondary plateaus. As such, metal fibers play an important role in the formation of friction film along with abrasive and lubricant materials.

This study investigates the strength of Hastelloy X nickel-based superalloy and AISI 304L austenitic stainless steel composite joint produced by laser welding. Two pieces of 1mm thick dissimilar plates are butt jointed together on a sheet fixture and welded using a pulsed Nd-YAG laser beam. In the welding process, different values are used for welding power, laser beam pulse width and welding speed. Values for the beam frequency, shielding gas flow rate and beam diameter are kept constant on the surface of the work piece. After welding, suitable specimens were cut from sheet components and subjected to high-temperature tensile tests and constant load creep. The results of tensile and creep tests show that by choosing the right laser welding parameters, a proper bonding between Hastelloy X and AISI 304L alloys can be achieved. In some samples, the joints strength is higher than the corresponding value of base alloy strength (AISI 304L), and the failure occurred in the base alloy region. Optical and scanning electron microscopes have also been used to examine the structure of the joint. The data from these microscopes shows that joints almost free of defects can be achieved by optimizing the beam power, welding speed and pulse width.