https://macs.semnan.ac.ir/ Mechanics of Advanced Composite Structures en daily 1 Thu, 01 Apr 2027 00:00:00 +0330 Thu, 01 Apr 2027 00:00:00 +0330 https://macs.semnan.ac.ir/article_10400.html This study determines the elastic constants and evaluates the in-plane mechanical behavior of hexagonal and re-entrant (auxetic) honeycomb structures under large deformations by utilizing the Absolute Nodal Coordinate Formulation (ANCF) for modeling elastic forces and applying periodic boundary conditions (PBCs) to precisely control deformations at the boundaries. A representative volume element (RVE) was selected, and static equations were derived by modeling cell walls as beam elements using the ANCF based on the finite element method (FEM) and the periodic boundary conditions were subsequently implemented. After solving the static equations, analytical validation was performed for small deformations. The results demonstrate that honeycomb structures exhibit nonlinear behavior under large deformations, which is crucial to determine for dynamic applications. In addition, the proposed model provides an effective technique for determining elastic constants and evaluating the mechanical behavior of honeycomb structures under large deformations, with applicability to various cellular geometries and piezoelectric cell structures. https://macs.semnan.ac.ir/article_10399.html The present study investigates the mechanical and tribological behaviour of Al alloys and Al/ZrO₂ ex-situ composites, focusing on their microstructural evolution and property enhancement. Al/ZrO₂ composites were synthesised using stir casting, incorporating 1, 3, and 5 wt.% ZrO₂ particles. Alloys and composites were characterizedusing X-ray diffraction (XRD), optical microscope (OM), and scanning electron microscopy (SEM)to analyse phase formation, particle distribution. Microstructural analysis revealed homogeneous dispersion of ZrO₂ particles, promoting load transfer and matrix strengthening. Mechanical properties were analysed using Vickers microhardness and uniaxial tensile tests, demonstrating substantial increases in hardness and tensile strength with increasing ZrO₂ content due to grain refinement, dislocation strengthening, and Orowan strengthening mechanisms. Tribological performance was evaluated using a pin-on-disc apparatus under varying loads (10N- 30N) and sliding speeds (1 m/sec -3 m/sec). The Al/ZrO₂ composites exhibited a significant reduction in the wear (up to 50%) compared to the unreinforced alloy, attributed to the load-bearing capacity of ZrO₂ particles and the formation of a protective tribolayer. Surface morphology of the worn samples, analysed using SEM, indicated a transition from abrasive to mild adhesive wear with the addition of ZrO₂. Further topographical parameters were studied using atomic force microscopy (AFM), which suggests a decrease in surface roughness from 0.87 µm to 0.70 µm at3wt. % of ZrO2 compared to the base alloy. https://macs.semnan.ac.ir/article_10508.html In this research, the fracture behavior of 3 mol% yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) dental ceramics is investigated. The focus is on the tetragonal (t) to monoclinic (m) phase transformation using ABAQUS and bond-based peridynamics. We conducted two-dimensional simulations of a single grain undergoing uniform dilational expansion within a homogeneous m-phase environment. The effects of transformation time, biaxial stress, and strains on fracture were analyzed. It was found that increasing stress in the surrounding t-phase elevated the elastic strain energy associated with the transformation. By varying stress from -1.1 GPa to 400 MPa, elastic strain energy started to decrease from 3.41, 3.32, 3.11, and 2.85 pJ at fracture strain values of S0= 0.00711, 0.00553, 0.00395, and 0.00237, respectively. These correspond to reductions of 83%, 87%, 90%, and 96%. In addition, damage fractions increased from 0.001, 0.002, 0.003, and 0.004 to 0.005, 0.011, 0.022, and 0.058, respectively. This demonstrates the significant impact of applied stress on the fracture mechanics of 3Y-TZP. Moreover, increasing the elemental parameter S0 from 0.00237 to 0.00711 in the simulations corresponds to a considerable decrease in defect density, resulting in a substantial increase in the total energy required for material division from 0.25 to 2.2 J/m2. https://macs.semnan.ac.ir/article_10278.html Industries like aerospace, automotive, marine, and transportation require materials that are lightweight yet strong, durable, and impact-resistant. To meet these demands, advanced composite materials are being developed using natural fibres such as bamboo and jute, which are eco-friendly, abundant, and cost-effective. When combined with synthetic fibres like glass, known for its heat resistance and interfacial strength, the mechanical properties of these composites improve significantly. Fabricated using the hand lay-up method with a 70% epoxy and 30% fibre ratio, these materials were tested per ASTM standards. Studies have shown that hybrid composites reinforced with bamboo, jute, and glass fibres offer enhanced tensile, flexural, hardness, and impact strength. The S1 stacking sequence performed best, with a tensile strength of 95 MPa, modulus of 1028MPa, flexural strength of 195 MPa and modulus 54 GPa, impact toughness of 12 J/mm, hardness of 87 RHN, and thermal conductivity of 0.26 W/m·K. These composites are lightweight, strong, and thermally efficient, making them ideal for rail, power, automotive, marine, and aerospace applications. https://macs.semnan.ac.ir/article_10281.html The present study investigates the bending characteristics of a two-dimensional functionally graded curved porous beam using unified shear deformation theory (USDT), incorporating shear functions and a modified power law. This approach integrates potential energy, the neutral surface concept, and equilibrium equations to enhance accuracy. Various boundary conditions, such as simply supported (SS), clamped-supported (CS), clamped-clamped (CC), and clamped-free (CF), are employed in the analysis. A metal-ceramic functionally graded beam with both even and uneven porosity is modelled. The symmetrical material gradation ensures that the physical neutral surface aligns with the geometrical neutral surface, which is considered in the formulation. A displacement-based formulation and energy principles are adopted, providing a more comprehensive and precise analysis of the beams. This method accounts for higher-order shear deformation effects, eliminates the need for shear correction factors, and effectively manages the continuous variation of material properties in FGMs. Consequently, it leads to improved predictions of structural behavior, making USDT particularly valuable for advanced material applications. The Hamilton method is employed to derive equilibrium equations for the beams, which are subsequently solved using the Kuhn-Tucker conditions. https://macs.semnan.ac.ir/article_10401.html This study investigates the vibrational behavior of a functionally graded beam using the doublet mechanics theory. This theory accounts for interactions between constituent atoms within a structure, enabling consideration of atomic-scale structure and orientation relative to the beam axis. While classical Euler–Bernoulli and Timoshenko beam theories are commonly used within the framework of doublet mechanics, they typically neglect key terms associated with shear deformation effects. To overcome this limitation, the present research introduces the novel application of higher-order shear deformation theories (HSDTs) within the doublet mechanics framework. This approach, not previously explored in the literature, provides more accurate predictions of vibrational characteristics. The results reveal that employing doublet mechanics can significantly influence natural frequencies, with deviations of up to 5%. https://macs.semnan.ac.ir/article_10480.html The research presents how Carboxyl Terminated Butadiene Nitrile (CTBN) and Epoxy Terminated Butadiene Nitrile (ETBN) types of Reactive Liquid Rubber (RLR) influence epoxy resins through rheological, thermal, and mechanical property assessments. The use of recycled waste rubber creates sustainable high-performance additives through waste material transformation. Various mechanical, thermal, and rheological tests assessed the effects of CTBN and ETBN concentrations on their viscosity behaviour, mechanical properties, and curing process of the epoxy system used. The thermal stability of the ETBN and CTBN systems was analyzed by using Thermogravimetric Analysis (TGA) to determine decomposition temperatures and stability measurements. A complete set of mechanical tests measured tensile strength, flexural strength, and impact strength. Toughness improvements reached their peak with 2.5 wt.% ETBN addition resulting in a 42.2% increase in ultimate tensile strength, a 103.8% increase in tensile modulus, a 26.9% improvement in toughness, and a 67.65% increase in impact strength while maintaining all other properties. Also, 5 wt.% CTBN incorporation into the epoxy polymer leads to 30% increment in ultimate tensile strength, 49.5% increase in ultimate flexural strength, 68% increase in tensile modulus, and 300% increase in impact strength. So, both CTBN and ETBN are said to be effective tougheners that can be used to enhance the toughness of the overall matrix system while balancing other mechanical properties. The investigation highlights how the termination chemistry affects phase separation and interfacial adhesion, ultimately leading to improved performance for its applications in automotive and aerospace industries. The innovative use of recycled ETBN and CTBN thus creates a way for the development of sustainable solutions that deliver economic benefits and environmental advantages. https://macs.semnan.ac.ir/article_10487.html Composite materials, particularly glass and carbon fibre composites, are widely used in aerospace, automotive, and defence applications because of their excellent strength-to-weight ratio and superior mechanical performance. However, their structural integrity can be severely compromised when subjected to high-intensity dynamic loads such as close-range explosions. His study presents a comprehensive finite element analysis (FEA) and optimization methodology to evaluate and improve the blast resistance of these composite plates under surface contact explosive loading. The numerical model was developed in LS-DYNA, where the laminates were modeled with 3D solid elements and governed by the Tsai–Wu failure criterion to predict ply failure behaviour. Model validation was carried out by comparing numerical predictions with experimental data from the literature, showing good agreement in terms of delamination area, perforation, and damage distribution.Following validation, a Genetic Algorithm (GA) implemented through LS-OPT was employed to optimize the laminate lay-up sequence, aiming to maximize the safety factor. The optimization yielded significant performance improvements—raising the safety factor by up to 63% and reducing delamination damage by up to 33%. Furthermore, the effect of explosive stand-off distance was analyzed, revealing its critical role in mitigating structural damage. The proposed framework provides a reliable and practical numerical tool for designing and optimizing blast-resistant composite structures, offering valuable guidance for aerospace, defence, and automotive engineers to develop lighter and safer structural components capable of withstanding severe explosion environments. https://macs.semnan.ac.ir/article_10472.html Electromagnetic wave-absorbing polymer nano-coatings are recognized as important for advanced electromagnetic shielding and wave management applications. In this study, a novel two-phase Al₂O₃/NbC polymer nano-composite within an epoxy resin matrix is introduced, incorporating dual silane surface treatments (APTMS and GPTMS) to enhance inter facial bonding and ensure uniform dispersion of the reinforcing materials. A designed of experimental (DOE) plan was implemented prior to the fabrication process to determine the optimal weight fractions of aluminum oxide (Al₂O₃) and niobium carbide (NbC). Subsequently, chemical bonding, particle surface modification, and matrix homogenization were performed, and the samples were prepared in rectangular molds suitable for electromagnetic rectangular wave guide measurements in the 8.2–12.5 GHz range. The structural and chemical characteristics were analyzed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results obtained from electromagnetic absorption and reflection measurements within the 8.2–12.5 GHz frequency range show that sample No.1, with a higher NbC content, demonstrates stronger absorption near 9.5 GHz but reduced performance at higher frequencies. Sample No.2, containing a balanced ratio of Al₂O₃ and NbC, exhibits a more uniform response across the frequency range, while sample No.3, with a higher Al₂O₃ fraction, presents improved impedance matching, enhanced dielectric loss, and absorption exceeding 80% throughout 8.2–12.5 GHz, accompanied by a reflection reduction of approximately 6%. These results indicate that tuning the weight fraction of the two phases allows optimization of broadband absorption performance. Overall, the dual-phase Al₂O₃/NbC system with surface-modified particles can achieve efficient, broadband electromagnetic absorption, offering potential for advanced shielding and wave control applications for aerospace industries. https://macs.semnan.ac.ir/article_10481.html This study focuses on the design and development of an advanced armor system that combines perforated steel plates and ceramic with a zigzag geometry to enhance ballistic protection. The objective is to provide effective defense against high-velocity armor-piercing threats while maintaining lightweight characteristics. The armor system consists of a perforated steel plate integrated with a base made of zigzagged silicon carbide (SiC), aluminum, and Kevlar. The novel aspect of this design lies in the modification of the ceramic surface, where a contoured geometry is implemented to increase energy absorption and projectile deflection upon impact. Additionally, conical perforations are introduced in the steel plate to enhance asymmetric impact behavior, contributing to the armor's ability to deflect or fragment incoming projectiles. Finite Element Analysis (FEA) using LS-DYNA simulations and design of experiment software were employed to determine the optimal geometric configuration of the perforations and ceramic surface. This analysis focused on parameters such as the angle of the conical hole, the arrangement and thickness ratio of the aluminum and Kevlar layers, and the air gap between the perforated plate and the base armor. The results indicate that the combination of the perforated steel plate and the modified ceramic surface significantly improves ballistic performance by enhancing the armor's capacity to dissipate impact energy and prevent penetration. The developed system demonstrates its effectiveness in protecting against armor-piercing threats while offering a lightweight solution for military and civilian defense applications. https://macs.semnan.ac.ir/article_10482.html Aluminum-based composites reinforced with Mg₂Si particles are valued for their engineering properties. This study examines how cutting parameters and Ag, Bi, and Sr additives affect tool wear and surface roughness during both dry and wet turning of Al–Mg₂Si composites. Using a Taguchi design, we varied spindle speed, feed rate, depth of cut, and lubrication to determine their relative impacts on tool wear area and surface roughness. Composites were fabricated through casting and examined using SEM–EDS techniques to assess microstructural characteristics and wear morphology. Feed rate emerged as the most critical factor, while wet machining with a biodegradable fluid markedly improved both tool life and finish. Among the materials tested, the composite containing all three additives delivered the lowest wear and finest surface. Specifically, the 14.47% improvement in dispersion uniformity was observed when all additives were used, while tool wear was reduced by 24.04%, and surface roughness improved by 18.94% under optimized machining conditions (spindle speed of 1000 rpm, feed rate of 0.12 mm/rev, and depth of cut of 1 mm). Regression modeling supported the experimental findings and demonstrated strong predictive accuracy. Confirmation trials under optimized conditions verified these trends. These results highlight the role of additive elements not only in modifying microstructure but also in enhancing machinability. The findings provide clear guidance on selecting additive combinations and machining settings to maximize productivity, extend tool life, and achieve superior surface integrity in Al–Mg₂Si composite turning. https://macs.semnan.ac.ir/article_10484.html Resole phenolic resin, valued for its excellent heat resistance, strong adhesion, and chemical stability, has long been utilized in aerospace, automotive, and protective material applications. However, its relatively low toughness and brittleness limit broader use. In this study, the thermal and mechanical characteristics of phenolic composites were improved by incorporating Polytetrafluoroethylene (PTFE) powder, Silicon carbide (SiC) particles, carbon, and high-silica fibers. A D-optimal response surface methodology (RSM) design was employed to evaluate the effects of fiber type, curing temperature, and particle loading. Scanning electron microscopy (SEM) analysis revealed that the addition of reinforcing particles altered fracture morphology by promoting crack deflection and improving resin–fiber interaction. Differential scanning calorimetry (DSC) results confirmed a 7% increase in glass transition temperature (Tg) with 10% particle loading, indicating enhanced thermal stability. Mechanical testing demonstrated that the addition of 10 wt% reinforcing particles enhanced both tensile and flexural properties, regardless of the fiber type; however, the fiber type itself had a significant influence on performance. Carbon fiber composites achieved the highest tensile strength (264.8 MPa), which was 13% above hybrid laminates (235.2 MPa) and 185% above high-silica composites (93.0 MPa). Conversely, hybrid laminates exhibited the best flexural strength (219.9 MPa), exceeding carbon by 72% and high-silica by 150%. Quantitative ANOVA validation confirmed the reliability of the developed models for both tensile and flexural strength. Optimal parameters—10% particle loading, 180°C curing with carbon fibers for tensile strength, and hybrid fibers for flexural strength—offer clear, actionable guidance for industrial applications. https://macs.semnan.ac.ir/article_10485.html Its consequences are important both from an ergonomic point of view and from a health point of view for operators of handheld-agricultural machinery, especially in terms of the inefficiency of traditional rubber isolators against low frequencies. This work will be affirmative proof of the validity for the design and experimentally optimized elliptical composite leaf spring system for passive vibration isolation in such equipment. Two springs materials; EN48 and SS304 having finite element analysis (FEA) outputs and CAD model were analyzed for their structural behavior under dynamic engine loads. Composite liners of E-glass/epoxy were combined with varying thickness (5mm and 6mm) and fiber orientation (0° and 45°) to improve damping property. To assess 16 configurations of design using vibration displacement and acceleration responses a Taguchi L16 orthogonal array was used. The best configuration including an SS304 spring (1.5 mm) and a 5 mm liner that was 45° oriented achieved a 35% displacement and 57.7% acceleration reduction as compared to baseline configurations. Results confirmed the compliance to ISO 5349 exposure limits, reiterating the system’s effectiveness in real world scenarios. This work proves the potential use of the elliptical composite springs as a robust, comfortable solution to reduce the HAV in the compact agricultural tools. https://macs.semnan.ac.ir/article_10486.html Components made of glass fiber reinforced polymers often fail under interlaminar shear loading conditions, which can significantly compromise their structural performance. To solve this problem, the piezoresistive effect of graphene nanoplatelets integrated into the glass fiber reinforced polymers is proposed as a technique to monitor and detect interlaminar shear failure. For that, short beam shear specimens were prepared from glass fiber reinforced polymers modified with graphene nanoplatelets, and changes in electrical resistance caused by quasi-static bending forces were recorded to monitor the electromechanical behavior and failure mode. The interlaminar shear strength was obtained at around 30 MPa for both composites (0.75 and 1 wt.% graphene nanoplatelets). Results indicate that the incorporation of graphene nanoplatelets has a minimal effect on the electromechanical behavior curves and both concentrations (0.75 and 1 wt.%) provide good electrical sensing capability for interlaminar shear failure in glass fiber reinforced polymers, which can be used as an active tool for health monitoring applications across a wide variety of industrial applications, especially where this failure mode may occur. https://macs.semnan.ac.ir/article_10491.html This study investigates the thermoelastic behaviour of laminated composite beams with symmetric (0/90/0) and asymmetric (0/90) layerups subjected to sinusoidally distributed thermal line loads. A quasi 3D shear deformation theory incorporating parabolic and trigonometric through thickness functions based on Reddy’s refined model forms the core analytical framework. The governing equations are derived from the principle of virtual work and solved in closed form via a Navier’s type series. The classical beam theory and first order shear deformation theory are employed solely for comparative analysis. The thermal line load model, representing realistic non-uniform heating scenarios enables assessments of coupling effects due to laminate asymmetry. Results reveal that asymmetric configurations exhibit significant thermal coupling leading to higher displacements and stress concentrations, while symmetric laminated beam offer improved thermal stability. A MATLAB based computational tool supports the analysis. The findings underscore the critical role of stacking symmetry in mitigating thermal deformations, guiding the design of reliable composite structures for thermally demanding environments. https://macs.semnan.ac.ir/article_10513.html Understanding the impact of aspect ratio on the deformation and load-bearing capacity of aluminium matrix composites is crucial in tailoring their forming performance. In this study, aluminium alloy (AA) 6082/Metakaolin (MK)/nano silicon nitride (Si₃N₄) composites containing 7.5 wt.% MK and 1.5 wt.% Si₃N₄ were fabricated using ultrasonic cavitation-assisted stir casting and tested under quasi-static compression with cylindrical specimens of aspect ratios 0.5, 1, and 1.5 in both as-cast and T6 heat-treated conditions. The results showed that lower aspect ratios significantly enhanced workability. The as-cast composite at aspect ratio 0.5 sustained compressive deformation up to a 50% reduction in height without visible cracks, achieving a maximum axial stress of 573.25 MPa. The T6 heat-treated samples exhibited a maximum compressive strength of 543.31 MPa and fractured at lower strain due to embrittlement caused by eutectic Si and Mg₂Si phases. Microstructural analysis indicated pore closure as the governing deformation mechanism in as-cast specimens, while brittle fracture dominated the T6 samples. Instantaneous strain hardening exponent (nᵢ) and strength coefficient (kᵢ) trends confirmed contributions from both matrix and geometric work hardening during deformation. In order to predict the workability parameters for different aspect ratios and loadings, response surface methodology (RSM) and artificial neural network (ANN) were employed. ANN yielded superior prediction accuracy for the workability parameters compared to RSM. These findings confirm that aspect ratio strongly controls the deformation mechanisms, with shorter cylindrical specimens offering optimum workability for practical forming operations. https://macs.semnan.ac.ir/article_10514.html This study is focused on evaluating the behaviour of use of alternatives for cement, namely, Ground-Granulated Blast Furnace Slag (GGBS) and Nano Silica (NS), on the the mechanical, microstructure, and structural behavior of in reinforced concrete (RC) slabs. Concrete was made with various dosages of GGBS from 0% to 50% at a rate of 5% and NS dosage from 0.1% to 1% at an interval of 0.1%. Compressive and tensile strength of concrete was evaluated along with microstructural characteristics using Scanning Electron Microscopy (SEM). The optimum dosages ware found to be 10% GGBS and 0.3% NS by cement weight. This optimum dosage, was used in making RC slabs with dimensions 1200 x 1200 x 100 mm, varying the slab thickness. To determine the stiffness and load-bearing capacity of the slabs, two-point loading was applied. Use of GGBS and NS results in high-density and high- strength concrete. Such research works highlight the prospective use of GGBS and NS in sustainable construction, encouraging cost-effective, eco-friendly practices with innovations in concrete technology. https://macs.semnan.ac.ir/article_10515.html Surface treatment preparation plays a key role in the strength of adhesive joints, particularly in single-lap joints. The most optimal surface conditions must be reached to achieve a strong joint. This research aims to achieve the maximum shear strength of single-lap Al/composite joints using the laser surface treatment. Four different parameters are considered, namely power, speed, the energy density of the laser on both adherends, and the laser hatch distance (HD). To predict the strength of the connection, the Design of Experiment method has been used. Several single-lap specimens with different surface parameters were created and analyzed experimentally. The results show that the hatch distance had the greatest effect on the shear strength of the specimens, followed by the mutual impact of the Al laser surface treatment power on the HD, the mutual effect of the speed of laser in Al surface treatment on the HD, and the laser power in Al surface treatment and the speed of Al laser surface treatment had the greatest effect on strength. Additionally, it was found that there is no direct or inverse relationship between the speed and laser power parameters. The optimal design obtained has a laser surface treatment speed of 1000 mm/s and 1200 mm/s, and laser power of 18 and 9 watts for Al and composite, respectively, and 50 micrometers for HD. The obtained optimal specimen has an average shear strength and failure force of 8.6 MPa and 6.676 kN, respectively, which shows about 102% improvement compared to the sandpaper method. https://macs.semnan.ac.ir/article_10516.html The present work focuses on primary objectives to analyse the dimensional stability of machined samples through kerf width and taper angle. Further to optimize the process parameters to obtain optimum results. RSM-BBD approach has been used to design the experiments. We prepared Mg based metal matrix hybrid composite samples using stir casting process. Prepared samples are machined on CNC wire cut EDM. Matrix of Mg alloy AZ91 (94%) and reinforcement of SiC (4%) and Al2O3 (2%) powder is selected. Machined samples are observed for kerf width and taper angle calculations followed by the optimization of process parameters to obtain optimum kerf width and taper angle. Optical microscope is used to measure the kerf width with 10x magnification. Top kerf width (Tkw), bottom kerf width (Bkw) and taper angle have been calculated and parametric plot is shown. Results obtained shows that pulse on time and current is most significant factor in obtaining the optimum values of output responses. Optimum values of top kerf width and bottom kerf width are obtained at Ton = 18µs, Toff = 5µs, I = 3A & WS = 10.4m/s and Ton = 18µs, Toff = 9µs, I = 3A & WS = 3.12m/s respectively. Optimum value of taper angle is obtained at Ton = 30µs, Toff = 7µs, I = 3A & WS = 10.4m/s. https://macs.semnan.ac.ir/article_10517.html Multi-layered composite materials with improved capabilities are fiber metal laminates (FMLs). Damage to the composites, such as delamination, decreases their stiffness and modifies the dynamic behaviour of the structures. Vibration analysis can be a good way to forecast delamination since the loss of stiffness affects the natural frequencies, mode shapes, and other structure features. In this research, vibrational analysis of aluminum and mild steel-based carbon fiber metal laminates are considered with delamination. A total of 36 fiber metal laminate specimens of 3/2 configuration with various delamination area and situated at various interface were considered for vibrational analysis, which was carried out experimentally and by FEA software. The analysis is done on healthy and delaminated specimens under clamped-free, clamped-clamped condition. The results demonstrate that the proposed method indicates that delamination reduces the natural frequency of the FML. The decrease in natural frequency can be used for damage detection which will act as base for an inverse problem. https://macs.semnan.ac.ir/article_10518.html In this paper, a combined analytical and numerical framework is presented to reduce or eliminate biaxial bending and torsion in ionic polymer–metal composite (IPMC) actuators. The problem is formulated based on the coupled Nernst–Planck–Poisson model for ion transport and electric field distribution, together with the Euler–Bernoulli beam theory for mechanical response. the main innovation of this study is the integrated design of a two-dimensional symmetric electric field distribution V(x,y) and modified electrochemical–mechanical boundary conditions that simultaneously suppress transverse and torsional gradients. In addition, field- and time-dependent mechanical moduli E and G are introduced to represent viscoelastic effects and electro-mechanical softening more realistically. this comprehensive coupling allows the model to maintain both mathematical and physical symmetry, leading to a uniform ion distribution and balanced bending–torsion response—an advancement beyond previous electro-chemo-mechanical models that considered symmetry only partially or in a single direction. numerical results, using realistic dimensions and a 5 V applied voltage, show that the proposed symmetric field design can reduce transverse bending by up to 87.5% and torsional strain energy by up to 88%. These findings demonstrate that optimized electric field design, appropriate boundary conditions, and field-dependent viscoelastic modeling can substantially enhance IPMC actuator performance and minimize undesired biaxial deformation. https://macs.semnan.ac.ir/article_10519.html Concrete two-way slabs could be subjected to impulse load due to accidents, which force the structural member to undergo strain hardening faster than its ability to dampen and absorb much of the applied energy, which has not previously investigated in the literature. Theoretical and numerical models were developed and validated against experimental results to explore this behavior. A reinforced concrete square slab of 1 m length and 0.08m thickness was simulated with several case studies investigated, such as the impulse load intensity, concrete compressive strength magnitude, the model's free vibration, and the model solution. It was concluded that the slab's response under impulse load depends, to the first degree, on the impulse quantity. If this sudden load equals two-thirds of the static load, the model starts to show visible cracks. Furthermore, the maximum displacement does not necessarily occur at the instant of loading; unlike static conditions, the designer can expect the higher deflection several seconds after the applied load is applied. https://macs.semnan.ac.ir/article_10579.html This literature review analyzes the latest modeling frameworks for composite structures and functionally gradient materials, emphasizing Equivalent Single-Layer (ESL) theories, layer-by-layer formulations (layerwise) and the Carrera Unified Formulation (CUF) as well as their applications to beams, plates, sandwich structures, and materials with functional gradients (FGM). Our aim is to clarify the modeling trade-offs that determine the theory choice based on the structure's thinness, heterogeneity through thickness, and complexity of multilayer stacks. ESL approaches, ranging from classical theory to first- and higher-order shear models, are distinguished by their low computational cost and ability to conduct large-scale analyses, but often require enriched kinematics or specific corrections to ensure sufficient accuracy in the case of thick structures, marked gradients, or interlaminar effects. Layerwise models, which include discrete and mixed formulations, offer a more precise description of fields across thickness and interfaces, but come with an increased number of degrees of freedom enabling them to analyze sandwich and FGM structures that are susceptible to delamination. The CUF is analyzed as a unifying framework that allows for systematic priority of kinematics and controlled adjustment of the trade-off between accuracy and cost, with a goal of convergence towards predictions close to three-dimensional elasticity. Based on the identified works, a comparative synthesis is proposed in terms of accuracy, numerical robustness, and computational cost for the analysis of flexure, vibration, and buckling, as well as for some nonlinear and multiphysical extensions. https://macs.semnan.ac.ir/article_10580.html This study presents a comprehensive evaluation of the mechanical performance of a segmented 3D-printed composite prototype blade. To assess its stiffness characteristics, the blade was subjected to systematically applied load levels in the flapwise direction. The experimental campaign enabled detailed characterization of the blade's stiffness and the initiation and evolution of damage as a function of applied loading and the number of fatigue cycles. A statistical analysis was performed to quantify the uncertainty and repeatability of the measured results. A specialized test bench was designed and constructed to accommodate fatigue testing of blades measuring 712~mm in length. The blade was subjected to controlled cyclic loading while its mechanical response was continuously monitored using a high-resolution imaging system. The collected data revealed a significant increase in total deformation energy of 77.5\%, particularly near the root (point~1), and a corresponding decrease in stiffness of 77\% after cyclic loading in the flapwise direction. These results provide critical insights into the blade's structural health and dynamic response during service and have informed improvements in the manufacturing process to ensure that the final products meet stringent reliability and safety standards under severe operating conditions. Uncertainty and repeatability were further evaluated by testing two blades with identical geometry and material properties, demonstrating that the derived results were accurate within an error margin not exceeding 10%. https://macs.semnan.ac.ir/article_10581.html The novelty of this research is to consider simultaneously forced vibration response of a nine-layer sandwich microbeam with homogeneous core reinforced by nanocomposite and piezo-magneto-electric layers under electric and magnetic fields in x and z directions as a self-sensing mass sensor at the end core layer. Also, the present study, the natural frequencies based on two methods, including the separation of variables for different B.C.’s and Navier’s method for S-S case are obtained. In this study, the effects of various parameters such as an added mass at the end of core, different Young's modulus to the density ratio, different properties of core, volume fraction of CNT, thickness ratio, aspect ratio, length of each layer to length of the core ratio, various distribution of carbon nanotube (CNT), material length scale parameter, electric and magnetic fields, input voltage on the frequency response function (FRF) amplitude are investigated. It shows that the natural frequency for C-C is higher than the other cases (C-S, S-S, C-F), because the stiffness of structures increases. Moreover, it shows that the natural frequency based on modified couple stress theory (MCST) is higher than classical theory (CT), because the material length scale parameter enhances the stiffness of a sandwich beam. It illustrates that the natural frequency for the FG-X distribution is higher than for other distributions, because the stiffness of the structure at the furthest distance from the neutral axis. It shows that with an enhance in the length ratio and aspect ratio, the natural freqeucny reduces, because the structure becomes softer. It considers that the effect of electric and magnetic fields is simulteneously higher than the other cases, because the stiffness of the micro beam enhances. The findings of this study can be crucial in the design of the engineering and medical industries. https://macs.semnan.ac.ir/article_10582.html The growing demand for lightweight structural materials with high impact resistance and energy absorption has driven research into hybrid composites. This study aims to develop a hybrid composite by combining natural basalt fiber with synthetic glass fiber and evaluating the effect of basalt fiber weight fraction on low-velocity impact performance. Composite laminates were fabricated using the hand lay-up technique with epoxy as the thermosetting matrix and reinforced with glass and basalt fibers at varying basalt contents: 0%, 18%, 36%, 52%, 72%, and 100%. Low-velocity impact tests were carried out as per the ASTM D7136 guidelines at three distinct energy levels: 20 J, 40 J, and 80 J. Internal damage was assessed using visual inspection and C-scan imaging, while ANOVA was used to statistically analyze the influence of fiber weight fraction on impact force, energy absorption, and damage area. Pure basalt laminates demonstrated high stiffness but brittle failure, while pure glass laminates absorbed more energy due to their higher ductility. The results revealed that among the hybrid laminates, the laminate with 52% basalt fiber demonstrated the most balanced combination of stiffness, energy absorption, and damage area, exhibiting strong hybrid synergy across all energy levels. These findings demonstrate the potential of basalt-glass hybrid composites as sustainable, lightweight, and impact-resistant materials.