An aircraft wing needs to display different mechanical behavior in different directions.1- stiffness in the spanwise (transverse to the corrugation) direction which enables the aerodynamic and inertial loads to be carried. 2- compliance in the chordwise (corrugation) direction which would allow shape changes and increases in surface area; whereas a corrugated sheet due to their special geometry has potential to use in morphing applications. Therefore, in this paper the mechanical behaviour of quasi-sinusoidal corrugated composites is studied by commercial FEM software ABAQUS and a simple analytical model which is used for the initial stiffness of the quasi-sinusoidal corrugated composites (Yokozeki model). The elongation and effective stiffness in longitudinal and transverse directions of quasi-sinusoidal corrugated skins and flat composites are calculated and compared together. Using first and second Castigliano's theorem and Bernoulli-Euler beam theorem can be used to calculate the deflection and rotational angle of a beam (sheet). In this research, different dimensions of quasi-sinusoidal element for unidirectional and woven composites of E-glass/epoxy are investigated. FEM results and analytical model are compared together. Then, the analytical model is validated by experimental results of plain woven E-glass/epoxy composites. The results of FEM, experimental and analytical simulations show that how a corrugated composite can afford with certainty larger deformation than the flat composite in using this analytical model to predict the mechanical behavior of quasi-sinusoidal corrugated composites. It was found that the corrugated composites display extremely high anisotropic behavior and have high tensile and flexural stiffness in transverse direction while exhibiting low stiffness in longitudinal direction of corrugation.

In this study, the microstructure, tensile, and fatigue behavior of the copper matrix composites reinforced by steel particles are investigated. The composite grades containing 2. 5, 5. 2, and 7. 4 wt% steel particles up to 90 μ, m in size are manufactured by the casting method. The microstructure of the composite samples is studied by scanning electron microscopy. The tensile and fatigue test samples are prepared and tested based on the ASTM standard. Adding 2. 5 wt% steel particles to the copper matrix increases the yield strength, tensile strength, and elongation of the pure copper by about 48, 21, and 4. 8%, respectively. The fatigue test results show that reinforcing the pure copper with 2. 5 wt% steel particles improves the fatigue life of the pure copper by 67, 31, and 86 percent in 60, 80, and 100 MPa amplitude stresses, respectively. On the other hand, further increasing the reinforcement particle content to 5. 2 and 7. 4 wt% causes unusual fatigue behavior and adversely affects the mechanical strength of the composite. Therefore, the fatigue life of the composite samples reinforced by more than 5. 2 wt% steel particles is not a function of the stress level and does not increase with the decrease of the stress.

In-situ alumina-zirconia composite bodies were fabricated by heat treatment of gibbsite-zircon-kaolinite mixture at 1450℃ . The current research investigated crystallization behavior and mechanical properties of the mentioned mixture in the presence of 5 wt. % MgO as an additive. X-ray diffraction (XRD) results showed that alumina, zirconia, and magnesium aluminosilicate were crystallized during the heat treatment at 1250-1550℃ . It was expected that mullite and zirconia were crystallized as the final phases; however, the addition of 5 wt. % of MgO changed the behavior of the mentioned mixture during the heat treatment at 1250-1550℃ . Energy diffractive X-Ray spectroscopy (EDS) reported that after heat treatment at 1450℃ , an Al3+-rich aluminosilicate phase was formed as the matrix of the composite. Crystallization of alumina and zirconia and the existence of the amorphous aluminosilicate phase formed a composite with appropriate hardness and mechanical strength. The diametral tensile strength and Vickers microhardness values of the final composite were 130± 7 MPa and 7. 49 ± 1. 2 GPa, respectively.

Effects of temperature on properties and behavior of a 20 vol % particulate SiC reinforced 6061 aluminum alloy and 6061 unreinforced Al alloy were investigated. Yield strength and elongation to failure were measured as a function of test temperatures up to 180^oC. In addition, the effects of holding time at 180^ oC on tensile properties and fracture mechanisms of the materials at this temperature were studied. The behaviors of the materials were characterized by using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray analyzer (EDS), X-ray diffraction (XRD), atomic absorption (AA), hardness measurement and image analyzing (IA). The results show that an increase in temperature leads to a decrease in the yield strength and increase in the elongation to failure of the materials. On the other hand, while increasing holding time at 180^oC produces an increase in the elongation to failure of the unreinforced alloy, it reduces the elongation to failure of the composite. It was also observed that reduction in yield strength with increasing holding time at 180^oC was faster for the composite material compared to the unreinforced alloy. The results from SEM, XRD, EDS, IA and hardness tests indicated that some chemical reactions had taken place at the interface between the reinforcement and the matrix alloy during holding the specimens at elevated temperature. Therefore, different trend in elongation to failure of the unreinforced alloy and the composite material with holding time at elevated temperature could be attributed to development of chemical reactions between the reinforcement and the matrix alloy at the interface.

This study investigated the effect of adding boron carbide microparticles (B4C) and titanium diboride nanoparticles (TiB2) on the microstructure, tensile strength, and hardness of A356 aluminum composite. In so doing, 2.5, 5, and 7.5 vol.% B4C reinforcements and 2.5 vol.% TiB2 reinforcement were added to the field by stir casting at 1000 °C using in situ process. The TiB2 nanoparticles were processed in situ by cryolite precursors (Na3AlF6), titanium oxide (TiO2), and potassium tetrafluoroborate (KBF4) in aluminum melt, and B4C microparticles were added directly into the melt. X-ray diffraction (XRD), optical microscope (OM), and scanning electron microscope (SEM) were used to investigate the microstructure and failure mechanism of the samples. Also, hardness and tensile tests were carried out to test mechanical properties. The results showed that addition of B4C first decreased and then increased the ultimate tensile strength compared to the sample without reinforcement. Moreover, the highest value of tensile strength was for the sample containing 2.5 vol.% of B4C and 2.5 vol.% TiB2, which showed a 235% improvement compared to the sample without an amplifier. However, the tensile strength of the sample containing 2.5 vol.% of B4C was reduced by 35% compared to the sample without reinforcement. The results of the hardness test showed a drop in properties of the samples containing 2.5% of B4C reinforcement. the highest value of tensile strength was for the sample containing 2.5 vol.% of B4C and 2.5 vol.% TiB2, which showed a 33% improvement compared to the sample without reinforcement.

In the present research, using a micromechanical approach, a novel analytical method was developed to predict the stiffness and damage initiation load of single-lap composite joints. The elastic and strength properties of fiber and matrix were used to characterize the elastic and strength properties of unidirectional composites. Based on the layup and geometrical parameters of the single-lap joint and using a nonlinear spring-mass model, the stiffness of the joint was predicted. Then, by defining the stress concentration factor and using the maximum stress failure criteria, the damage initiation load of the single-lap composite joint was predicted with a good accuracy. This model was used to simulate the mechanical behavior of single-lap joints with layups [− 45/0/45/90]𝑠 and[90/− 452/45]𝑠 . Composite joints with these two layups were manufactured and tested. A comparison between the results of the model and experiments shows maximum errors of 2. 17% and 3. 91% for joints with these two layups, respectively.

In this research, static stresses analysis of boron nitride nano - tube reinforced composite (BNNTRC) cylinder made of poly - vinylidene fluoride (PVDF) subjected to non - axisymmetric thermo - mechanical loads and applied voltage is developed. The surrounded elastic medium is modelled by Pasternak foundation. Composite structure is modeled based on piezoelectric fiber reinforced composite (PFRC) theory and a representative volume element has been considered for predicting the elastic, piezoelectric and dielectric properties of the cylinder. Higher order governing equations were solved analytically by Fourier series. The results demonstrated that the fatigue life of BNNTRC cylinder will be significantly dependent on the angle orientation and volume fraction of BNNTs. Results of this investigation can be used for the optimum design of thick - walled cylinders under the multi - physical fields.

The objective of the present study is to develop and investigate the swelling behavior of pH-sensitive Superporous Hydrogel (SPH) and SPH composite (SPHC). A novel superporous hydrogel containing poly (methacrylic acid-co-acrylamide) was synthesized from methacrylic acid and acrylamide through the aqueous solution polymerization, using N, N-methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. SPHCs were made in the same way, except for the using of Ac-Di-Sol as a stabilizer. The synthesized SPH and SPHC were characterized by Fourier-transform infrared spectroscopy, swelling kinetics, porosity, mechanical properties and scanning electron microscopy. The swelling of SPH and SPHC was sensitive towards the pH, ionic strength, and temperature stimuli. The study of the surface morphology of SPH using scanning electron microscopy showed a highly porous structure. SPH polymers showed higher swelling ratio but less mechanical stability compared to SPHC polymers, which showed lower swelling ratio but a higher mechanical stability. With a change in pH from acidic to basic, a considerable increase in swelling was observed. Since the prepared SPH and SPHC swell only in the basic pH, it may be concluded that SPH and SPHC can be used as the pH-sensitive drug delivery system.

The welding of materials by applying Friction Stir Welding technique is a new solid-state joining technique. The main advantage of this method compared to the traditional joining process is that it minimizes problem-related to metal resolidification as the method incorporates no melting phase. In this experimental work, the effect of friction stir welding (FSW) technique on the microstructure and mechanical properties of the cast composite matrix AA6063 reinforced with 7wt % SiC particles is studied. Friction stir welding, owing to the simultaneous effect of intense plastic deformation and frictional heat generated throughout welding, had impacts each on the reinforcement agents and the matrix alloy. FSW produced a notable reduction in the size of reinforcement agents and their homogeneous distribution in the weld region. It also induced the grain refinement due to dynamic recrystallization of the aluminum matrix alloy in the weld area. The frictional heat generated during friction stir welding had impacts on the growth, dissolution and reprecipitation of the hardening precipitates. The microstructural changes resulted in improved mechanical properties such as UTS, elongation, and hardness of the joint. A joint efficiency of 98. 84% was observed for the welded joint. The XRD and EDX analysis of the welded area confirmed that there was no formation of any other compound due to the frictional heat produced during welding. The SEM fracture morphology of the welded joint revealed that the fracture behavior was changed from ductile to brittle following to FSW.

In this research hybrid nanocomposite coating of Ni-P/Al2O3-SiC and Ni-P coating were codeposited and deposited by electrodeposition on copper substrate. Electrodepositions for both cases was done by DC current. Sic nanoparticles sizes and Al2O3 nanoparticles sizes which were used for preparing nanocomposite bath, were respectively 55nm and 50nm. Charactrizaton and surface morphology of coating were done by scanning electron microscopy and energy dispersive spectroscopy. The tribological behavior of the coatings were evaluated by pin-on-disc test, and microhardness of coating were also evaluated by Vickers microhardness test. Morphology of surface coating was evaluated by optical electron microscopy. Results show that adhesion of hybrid nanocomposite coating on copper substrate is perfect. Participation of nano Al2O3 particles and nano SiC particles, causes improvement in the microhardness and wear resistance of hybrid nanocomposite coating. High strength of nano Al2O3 particles and nano SiC particles, improved the microhardness and wear resistance of hybrid nanocomposite coating. Also, increases in current density for electrodeposition improve microhardness of Ni-P coating and Ni-P/Al2O3-SiC coating.