Mostafa Habibi

Thermo-elastic analysis of a metamaterial reinforced plate subjected to the mechanical and thermal loads is estimated in this paper. The formulation is done using the two-variable sinusoidal shear deformation theory, accounting for out-of-plane normal strain. This study employs an extension of the principle of virtual work into a three-dimensional framework to evaluate the structural response, including deformation, strain, and stress fields of a square composite plate embedded with graphene origami reinforcements under combined thermal and mechanical loads. The plate is manufactured from a Cu reinforced with the origami. The constitutive relations are extended using the material properties derived from the micromechanical models. A higher-order kinematic model with thickness stretch ability was developed for the derivation of the equations. To approve the solution method and derivation procedure, a verification investigation is developed. An enhanced kinematic description, incorporating extensibility and higher-order effects, enables precise analysis of the nanocomposite plate. This capability, combined with the structural efficiency achieved through a reconfigurable, compact geometry, supports potential deployment across sectors such as aerospace, automotive systems, and military technology, where reduced mass and tunable mechanical responses are critical.

This study examines how unit cell size affects the mechanical properties of a novel three‐dimensional‐printed cylindrical metamaterial structure made from acrylonitrile butadiene styrene resin via digital light processing additive manufacturing. It addresses key gaps in polymer‐based auxetic cylindrical reinforcements, particularly the lack of systematic parametric studies and experimentally validated models linking unit‐cell geometry to stiffness, strength, specific energy absorption (SEA), and auxetic behavior. The structure features a periodic lattice with tunable center diameter (CD) (4, 5.5, 7 mm) and width (2, 5, 8 mm), optimizing stiffness, strength, SEA, and auxetic behavior. Nine models were designed, fabricated, and tested via quasi‐static compression and finite element analysis in specialized software, with validation under 6% discrepancy. Width primarily enhances compressive strength (up to 360% increase from 160 to 657 N at 7 mm CD) and stiffness (49 N per mm to 431 N per mm), while CD tunes SEA (87.3 millijoules per gram to 231.6 millijoules per gram). Auxetic properties yield Poisson's ratios from −0.7 to −2.9, promoting radial contraction for stability. Optimal performance, with uniform strain and low stress concentration, is at 4 mm CD and 8 mm width, achieving 72.3 N per mm per gram stiffness per mass. This advances lightweight reinforcements for aerospace, civil, medical, and sports applications, enabling sustainable use through precise fabrication and analysis.

This study presents a novel bio-inspired round auxetic metamaterial whose unit-cell geometry is derived from the suture patterns observed in turtle shells. The design integrates natural inspiration with engineering optimization to achieve outstanding auxetic behavior, high energy dissipation, and superior mechanical resilience under compressive loading. The structure was fabricated using digital light processing (DLP) and analyzed through both experiments and finite element simulations in Abaqus. The experimental and numerical results show excellent agreement, with deviations below 5% in load–displacement response and buckling force, confirming the reliability of the simulation model. Parametric analyses reveal that increasing the unit-cell curvature radius enhances structural stiffness and raises the buckling force by up to 6%, while simultaneously reducing Poisson’s ratio by nearly 50%, thereby amplifying auxetic effects and radial contraction under load. Similarly, increasing the unit-cell thickness by 0.2[ ]mm significantly improves mechanical performance, raising the buckling force by approximately 70% and stiffness by around 45%. The findings underscore the novelty of this bio-inspired round metamaterial, demonstrating how geometric tuning enables tailored performance. The outcomes provide a framework for utilizing suture-inspired auxetic geometries in the creation of protective systems that combine low weight with structural robustness and enhanced energy dissipation.

This paper presents the design, fabrication, and mechanical characterization of rotational polygons auxetic metamaterial with a negative Poisson’s ratio. The remarkable auxetic behavior demonstrated by the metamaterial was achieved through its cell structure, which consists of four rectangular-shaped parts that rotate around a fixed point. The metamaterial’s mechanical performance was evaluated through experimental testing and finite element analysis (FEA) simulations. Simulations were performed using Abaqus computer-aided engineering (CAE), showing a good correlation with experimental results, with slight variations in force values during different stages of deformation. Stress distribution analysis showed that the maximum stress occurred at the junctions where the diamond-shaped units of the structure met, with a higher stress concentration observed in the lower half of the structure. Elastic strain distribution followed a similar pattern, with greater strain observed in the lower half, particularly in the central diamond-shaped gaps. Additionally, simulations of compression along the [ ]-direction revealed a more pronounced auxetic effect than [ ]-direction compression, where compression in the [ ]-direction caused contraction in the [ ]-direction. The force–displacement curve for [ ]-direction compression showed a higher peak force compared to [ ]-direction compression, with the force reaching a maximum of 3.26[ ]kN. The study also demonstrated that the stress and strain distribution during [ ]-direction compression closely resembled that observed at the end of the deformation in [ ]-direction compression. Furthermore, results reveal that the structure absorbs nearly four times more energy along the [ ] direction than the [ ] direction, attributed to its enhanced auxetic behavior in the [ ] direction. In terms of energy absorption, it was observed that a smaller gap size resulted in a higher capacity for energy absorption. The study underscores the enhanced energy absorption and auxetic response of the developed metamaterial, making it well-suited for use in energy dissipation and impact-resistant applications such as footwear.

This paper investigates the application of a novel foldable material in the sandwich plate subjected to multi-field loading. The analytical formulation is derived using the virtual work principle. The stretchable kinematic modeling is extended in order to arrive at more accurate results and modeling. The constitutive relations of the sandwich-reinforced core are derived using the overall and effective material properties of graphene origami-reinforced core using the Halpin-Tsai micromechanical model. The analytical solution is obtained in order to present the parametric results in terms of characteristics of the 3D nanofillers and multi-field loading parameters.

This analytical paper investigates the impact of initial electric potential as well as graphene origami characteristics on the deformable/foldable behavior of the sandwich double curved shell composed of a graphene origami-reinforced copper core sandwich by intelligent layers at top/bottom as sensor, actuator and energy harvester. The stretched and foldable model is extended for the description of the kinematic and constitutive relations, respectively. The variational-based formulation is extended for the derivation of the governing equations. The solution procedure is extended for the special boundary conditions to seek the impact of multi-field loading and material constituent characteristics on the electro-thermo-folding responses of the sandwich hybrid shell. As a quantitative result, one can arrive at 10% decrease in deflection with 2% addition of graphene origami reinforcement.

In the present study, we aimed to quantify the effects of COVID-19 restrictions and speech treatment approaches during lockdowns on autistic children using CBCL and neuro-fuzzy artificial intelligence method. In this regard, a survey including CBCL questionnaire is prepared using online forms. In total, 87 children with diagnosed Autism spectrum disorders (ASD) participated in the survey. The influences of three treatment approaches of in-person, telehealth and public services along with no-treatment condition during lockdown were the main factors of the investigation. The main output factors were internalized and externalized problems in general and their eight subcategory syndromes. We examined the reports by parents/caregivers to find correlation between treatments and CBCL listed problems. Moreover, comparison of the eight syndromes rating scores from pre-lockdown to post-lockdown periods were performed. In addition, artificial intelligence method were engaged to find the influence of speech treatment during restrictions on the level of internalizing and externalizing problems. In this regard, a fully connected adaptive neuro fuzzy inference system is employed with type and duration of treatments as input and T-scores of the syndromes are the output of the network. The results indicate that restrictions alleviate externalizing problems while intensifying internalizing problems. In addition, it is concluded that in-person speech therapy is the most effective and satisfactory approach to deal with ASD children during stay-at-home periods.