Journal of Science and Technology of Composites
Year:2018 | Volume:4 | Issue:4 |Papers Count:12

The purpose of this study is controlling the forced vibration of a layered composite cantilever plate embedded with shape memory alloys wires using classical and fuzzy controllers. The governing equations of motion of the composite plate including shape memory alloy wires are calculated using the classical laminated plate theory and the Hamilton principle. The Liang formula is also used to model the thermo-mechanical behavior of the shape memory alloys wire actuators. Then, the free vibration solution for the layered composite plate is calculated using semi-analytical Rayleigh-Ritz method and then is compared with experimental method. Comparison between the obtained natural frequencies of the composite plate and those of published experimental results confirms the accuracy of the purposed modeling and solution. Finally, three controlling system are designed to reduce the amplitude of vibrational displacement of the structure against forced vibrational excitations including PID controller, Fuzzy controller and PID-Fuzzy controller. Finally, the genetic algorithm is used to optimize the gain coefficients of the classic controller and the rules and parameters of the fuzzy controller to reduce the vibrational displacement amplitude of the plate. The obtained results show that the all designed controllers can reduce the steady-state vibrational displacement amplitude of the plate significantly, but the PID-Fuzzy controller has the best performance.

In this research, adhesively tubular single lap joints subjected to torsional and hygrothermal loadings are studied using the Differential Quadrature Method (DQM), in which the lateral deflections are taken into account. The analysis is based on the linear cylindrical shell theory. At first, governing differential equations of the tubes and the interfacing adhesive layer are expressed in terms of the displacement field components. The total structure is divided into the overlapping and non-overlapping areas. The differential equations of the overlapping area which do not have closed form solution, are discretized by implementing the DQM. Then, the equations of the total areas are solved simultaneously regarding their boundary and continuity equations, to find the circumferential and radial (lateral) displacements. Next, having known the displacement field components, the distribution of the peel and shear stresses in the interfacing adhesive are calculated. Results obtained from the presented DQM solutions are compared well with those of a published reference as well as those of an ABAQUS finite element model. Finally, using the DQM model, the influence of the adhesive layer thickness, the overlap length, and the changes in the temperature and relative humidity on the interfacing stress distributions are investigated.

In this study, mechanical properties, including elastic modulus, impact and tensile strengths of nanocomposites based on polypropylene and polyethylene linear low-density blends, in the presence of titanium oxide nanoparticles have been studied. Here, 0, 2 and 4 wt% titanium dioxide nanoparticles were added to the basic ingredients polypropylene / polyethylene linear low density with a fixed ratio of 60/40 wt. % to reach the final composition that was prepared using an extruder. Tensile and impact tests were carried out in order to determine the elastic modulus and impact strength of compounds. It was observed that the presence of titanium dioxide nanoparticles at 2 wt. %, elastic modulus and impact strength compared to the basic polypropylene/polyethylene linear low-density increase and the presence of higher level of titanium dioxide nanoparticles up to 4 wt. % decrease mechanical properties of compounds. It was also seen that usilng low weight percent of nano particles, increase impact strength of the samples up to 7 percenrt.

  Application of composites of two or more metals has been increased, aiming to increase productivity, in various sectors of industry in recent years. In this work an Al/Cu bimetal composite was prepared by casting Al melt into a Cu bush with 40 mm height and 79 and 84 inner and outer diameters, rotating at 1480 revolutions per minute (rpm), and 100, 150, 200, 300, and 400°C preheating temperature, respectively in a vertical centrifugal casting machine. Cooling rate increment, due to lower preheating temperature, not only lead to interface thinning but also it can modify microstructure. The results of scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis showed thatfour discrete layers have been formed from the Cu side, including AlCu2, AlCu, Al2Cu continuous layers, Al2Cu precipitates scattering in anomalous eutectic structures and finally α-Al/Al3Cu anomalous eutectic structure near the Al side.Micro hardness measurements showed that hardness of various presented phases decreases from outward to the inward.

Fiber metal laminates (FMLs) are a family of hybrid composite structures formed from the combination of metal layers sandwiching a fiber- reinforced plastic layer. Because of low weight and better mechanical properties in comparison with aluminum alloys and other composites, they have found a wide range of use in aerospace industriy. In the case of deep micro-cracks within the FMLs, they must be replaced. To avoid of replacing the FMLs, the self-healing phenomenon is an appropriate strategy to control the defects and micro-cracks. In this research a series of chopped micro glass tubes were employed to provide a self-healing system. These chopped micro glass tubes were filled with epoxy resin+hardener as a healing agent system. When the structure is exposed under loading condition, the created damages and micro-cracks rupture the chopped micro-glass tubes and the healing agent flows in the damage area and over a time span the defects will be healed and eliminated. The aim of this study is to find out the appropriate chopped micro-glass tubes volume fraction and the healing time to obtain an efficient healing. For this purpose, the chopped micro-tubes containing 4, 8, and 12 Vol.% were incorporated in epoxy- glass fibers composite and the tensile behavior observed for the specimens were assessed during different healing time. The highest healing efficiency of 58.3% was observed for the specimen with 8% healing agent.

In this research, effect of curvilinear fibers on the buckling load improvement of composite plates was studied. Two paths for curvilinear fiber were considered, namely, the linear variation of fiber angle and the nonlinear variation of fiber angle (constant curvature). The fiber orientation varies linear and nonlinear with the coordinates of plate in these two mentioned paths respectively. In the previous researches, linear variation of fiber angle was usually investigated. However, the results were not compared with those of the other paths. In this research, comparisons between the two paths of the linear variation of fiber orientation and the constant curvature of composite plates with and without cutout were performed. ABAQUS finite element software was used for modeling and analysis. Results show that for composite plates without cutoutsand with intended dimensions, material, lay-up and boundary condition, the constant curvature path caused four percent increase in the buckling load in comparison with the linear variation of fiber orientation path. According to applied boundary conditions, the mechanism of buckling load increase with curvilinear fibers is due to shifting the load from the center of plate to the side edges. Two geometries of cutout, circular cutout with different diameters and elliptical cutout with different aspect ratios were also considered. The results show that in the models with cutout by considering the manufacturing constraints, both paths have similar buckling load approximately.

In the present paper the compressive behavior of composite lattice truncated cone reinforced with and without carbon nanotube (CNT) is investigated using experimental and numerical simulation methods. Composite lattice truncated cone samples, made of glass/epoxy without CNT and reinforced with 2% wt. CNT are fabricated using filament winding process and tested under compressive axial force. Moreover, modeling of the structure is performed and numerical simulation is achieved using commercial finite element ABAQUS software and the results of compressive force vs. axial displacement are verified by the experimental data and good agreement is observed. Halpin-Tsai micromechanics model is also utilized in order to calculate the nanocomposite material properties and assigned in the numerical simulation. The effects of CNT weight percentage and coefficients of CNT dispersion within the epoxy resin matrix are investigated using numerical simulation method. The results showed that addition of CNT by 2% wt. to the epoxy resin of the composite lattice conical structure, enhanced the maximum carried compressive force by 44%. While addition of CNT more than 2% wt. causes the compressive strength to be decreased due to less dispersion quality and agglomeration and non-uniform dispersion of the CNTs within the epoxy resin.

Friction stir processing (FSP) is a surface improvement method. This process has been developed for facilitating the refinement of microstructure, improving the mechanical properties and producing the surface composite. The aim of this study is producing the surface copper-based nanocomposite with reinforcing SiO2 particles by friction stir processing for improving the mechanical properties. Therefore, 56 mm/min fixed traverse speed and 500, 710, 1000 rpm rotational speeds were used. Microstructures of samples were studied by optical and scanning electron microscopes. Optimum sample had a rotational and traverse speed of 500 rpm and 56 mm/min, respectively. The mechanical properties of the produced surface composite such as microhardness and tensile strength were evaluated and then compared with the base metal. The results of the mechanical tests showed that the microhardness and tensile strength were improved in comparison with base metal. The microhardness of the base metal and optimum sample were about 84Hv and 121 Hv, and tensile strength of them were 218 MPa, and 227 MPa, respectively. Finally, wear properties of surface composite were investigated. The results exhibited better wear behavior and also 28 percent decrease in friction coefficient of produced composite compared with the base metal.

In this research, CHARPY impact behavior of sandwich panel using the self-healing materials is considered. The sandwich panel consists of a PVC solid foam core between Carbon fibers composite faces with lay-up (0/90)s at the top and down structure. The thin glass tubes are filled by the self-healing materials and put among the composite layers of sandwich panel. The sandwich panel construction is made of handy lay-up, using Epoxy to bond the layers. The self-healing materials with (0.5, 1, 1.5) volume fraction are used among composite layers of sandwich panel. The destruction of sandwich panel using the self-healing materials is carried out by three point bending. After destruction, the healing will be started from zero point then 3 to 7 days have been considered to determine the effect of the self-healing materials of sandwich panel. CHARPY impact test are performed on the specimens at the mentioned time to investigate the effect of the self-healing material on the impact behavior of sandwich panel. The experimental results of CHARPY impact behavior of sandwich panel considering the self-healing materials illustrates that the most dynamic fracture toughness and healing efficiency belong to the specimen with 1.5 volume fraction after 7 days from destruction time comparing the control specimen. Using glass tubes particularly and the quantity of tubes also will be significant effect on increasing the strength of construction. By increasing the volume fraction and the time of healing, the healing efficiency of sandwich panel will be enhanced as well.

In this article for the first time local stiffness and attached mass dimensions is concerned.The effects of these parameters are analysed on dynamic behavior of thick laminated plates with attached mass that maked smart with shape memory alloy. In deriving governing equations, Gark-Kant’s higher order theory is used and effects of SMA and attached mass’s stiffness taken into account and finally vibration equations of thick plate carrying attached mass contain SMA is reached by using Hamilton’s principal. Then by means of Galerkin method, mass and stiffness matrices are extracted for achieving to a standard eigenvalue vibration problem. In this problem simply supported boundary condition is used for each four edges. Some important parameters such as ratio of local stiffness to stiffness of host structure and smart attached mass dimension on main frequencies of laminated thick plate is studied. A Comparative result with those in published references is presented. These numerical results show that local stiffness due to smart attached mass has a great role on dynamic behavior of thick laminated plates that if SMA didn’t active properly or ignore the effect of attached mass`s stiffness the dynamic response of system will have a lot of changes.

Pultrusion is a continuous method for producing profiles with a constant cross section. Because mechanical properties of pultruded composite are related to process parameters, developing a method for flow visualization is essential. In this study pultrusion of thermoplastic polymers was visualized and useful data about polymer flow and void formation during process was obtained. In this regard a straight (converging-parallel) pultrusion die with glass walls has been used for direct observation of process during pultrusion. Glass die has been heated using IR radiation for continuous heat supply and providing enough space to install visualization equipment. Also colored pellets and fibers were used for better visualization. Average velocity of a specific particle was measured in axial and lateral directions Vx=0.43cm/s and Vy=0.05cm/s. The average axial velocity in the entrance part of the die was measured twenty percent lower than puller speed and it gradually converged to puller speed at the end of the die. Volume of voids among the die has been reduced about 0.17 compared with first voids volume in die entrance. By using darcy law, average velocity and 7 bar measured pressure inside die, the axial permeability was calculated 5*10e-8 m2.

Accmulative roll bonding prcess is one of severe plastic deformation procidures for produce high strength-ultrafine grain materials. In this investigation, the new method of mixed accumulative roll bonding was used to produce Al-based composite reinforced with carbon nanotube and alumina. This method is mixed of Continual Annealing roll Bonding and cross roll accumulative roll bonding procedures. This process has two steps. The first step is reinforcement adding with accumulative roll bonding in four rolling passes and annealing for one hour and 350°C after any pass. The next step is accumulative roll bonding without adding reinforcement and annealing. After any rolling pass, strips rotate 90o in each step and then rolled. In this process 11 rolling passes perform on Al/ (1%wt CNT) composite and 9 rolling passes on Al/ (1%wt) CNT/ (2%wt) AL2O3 composite. X-ray diffraction result show that grain size is about nanometer in final rolling pass for both composite and with increase pass number increases tensile strength and elongation decrease first and then increases. strenght in Al/CNT/Al2o3 composite is higher than Al/CNT composite at the same rolling pass. FESEM picture show that reinforced distribution was well in final rolling pass.