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An appropriate constitutive model is essential for trustworthy numerical simulations and the analysis of material deformation behaviour during the metal-forming process. In the present work, the quasi-static warm tensile response of AZ31B alloy ranging from 200°C to 350°C with an incremental difference of 50°C and the strain rates from 10−1 to 10−3 s−1 is investigated experimentally and predicted using the Johnson–Cook and Zerilli–Armstrong (JC-ZA) constitutive model. The temperature and strain rate variation has a substantial impact on flow-stress behaviour. The model prediction efficacy is analysed based on the correlation coefficient (R), average absolute error (Δ), and their standard deviation (s). It is evident that the integrated JC–ZA model has better accuracy, with a correlation coefficient of 94.5%, average absolute error (Δ) of 3.97%, and a standard deviation of 5.67%. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the effect of glass fiber-reinforced polymer (GFRP) and carbon fiber-reinforced polymer (CFRP) strengthening materials on the static and dynamic behavior of reinforced concrete (R/C) beams subjected to progressive damage. Four identical beams, each strengthened with either GFRP or CFRP, are tested under a cyclic quasi-static loading pattern. Impact hammer tests are performed for undamaged states and various damage levels of the beams. The dynamic test data are analyzed using the Enhanced Frequency Domain Decomposition (EFDD) method to estimate the dynamic characteristics of the beams. In this context, the first three vibration modes in both vertical and horizontal directions are considered. Strengthening is applied to both pre-damaged and undamaged beams, enabling a comparison of their performance before and after the strengthening procedure. Beams strengthened with CFRP exhibit a higher load-bearing capacity and stiffness but also fail at lower displacement levels compared to those strengthened with GFRP, which demonstrate more ductile behavior. Furthermore, the modal frequency ratios indicate that the first vibration mode is more sensitive to damage than the second and third modes. This study highlights the effectiveness of both strengthening materials in enhancing the structural performance of both undamaged and damaged beams. [ABSTRACT FROM AUTHOR]

This paper presents a modified finite element analysis (FEA) model for predicting the axial compression strength of large-diameter concrete-filled steel tubular (CFST) stub columns, addressing the gap in research that has often focused on smaller diameters. The size effect, which significantly impacts the structural performance of large-diameter CFST columns, is a key focus of this study. The goal is to validate the accuracy and reliability of the modified FEA model by comparing its predictions with experimental data from the literature, specifically examining ultimate axial load capacity, failure modes, and deformed shapes. In addition to validating the model, this study includes a comprehensive parametric analysis that explores how critical geometric parameters such as the diameter-to-thickness (D/t) ratio and length-to-diameter (L/D) ratio affect the axial compressive behavior of CFST stub columns. By systematically varying these parameters, the research provides valuable insights into the load-bearing capacity, deformation characteristics, and failure mechanisms of CFST columns. Furthermore, the material properties of the steel tube—particularly its yield strength—and the compressive strength of the concrete core are investigated to optimize the design and safety performance of these columns. The results indicate that the FEA model shows excellent agreement with experimental results, accurately predicting the axial load-strain response. It was observed that as the diameter of the steel tube increases, the peak stress, peak strain, strength index, and ductility index tend to decrease, underscoring the size effect. Conversely, an increase in the yield strength and thickness of the steel tube enhances the ultimate strength of the CFST columns. These findings demonstrate the reliability of the modified FEA model in predicting the behavior of large-diameter CFST columns, offering a useful tool for optimizing designs and improving safety margins in structural applications. [ABSTRACT FROM AUTHOR]

Abstract Rock mass deformation and failure are macroscopic manifestations of crack initiation, propagation, and coalescence. However, simulating the transition of rocks from continuous to discontinuous media under cyclic dynamic loading remains challenging. This study proposes a hybrid finite-discrete element method (HFDEM) to model crack propagation, incorporating a frequency-dependent cohesive-zone model. The mechanical properties of standard sandy mudstone under quasi-static and cyclic dynamic loading were simulated using HFDEM, and the method's reliability was verified through experimental comparison. The comparative analysis demonstrates that HFDEM successfully captures crack interaction mechanisms and accurately simulates the overall failure behavior of specimens. Additionally, the effects of pre-existing flaw inclination angle and dynamic loading frequency on rock failure mechanisms were investigated. The numerical results reveal that rock samples exhibit significantly higher compressive strength under dynamic loading compared to quasi-static loading, with compressive strength increasing with higher cyclic dynamic load frequencies. Furthermore, by analyzing the strength characteristics, crack propagation, and failure modes of the samples, insights into the failure mechanisms of rocks under different frequency loads were obtained. This study provides valuable insights into crack development and failure of rocks under seismic loads, offering guidance for engineering practices.

Three levels of maximum sustainable tensile impact load (400, 450 and 500 N) of a small rectangular ripstop parachute canopy specimen stitched at a 45° seam angle have been studied manually. Using the scale-up approach, the proportionate peak sustainable opening shock force for T10, C9, and G11 low porosity canopies have been computed subsequently. This study also characterizes the small rectangular unseamed and seamed specimens at 0° and 45° seam angles under three levels of a maximum sustainable range of tensile impact and quasi-static loads. The ANOVA analysis shows that the fabric seam joining has a greater effect on the specimen's performance than the seam angle and applied load. It is also observed that the specimen degrades significantly more under impact load than the corresponding quasi-static load. Under quasi-static and impact loads, the seamed specimen exhibits more strength and elongation loss than the unseamed specimen. Further, the strength loss for the 0° seam angle is more than the 45° seam angle. The specimen with 45° seam angle exhibits better performance under impact and quasi-static load comparably and exhibits higher loss in elongation but still has higher breaking elongation than the specimen stitched with 0° seam angle at the same load level. [ABSTRACT FROM AUTHOR]

Lattice structures are well known for their high strength-to-weight ratio and energy absorption. The mechanical properties of these lattices depend upon the geometrical configurations and these properties could be altered by change in design. The current work aims to study the effect of material and lattice cells on static and dynamic mechanical properties of lattice cylinders. For the combined study of the material and structural effect, both materials need to be far different. Due to this, the lattice cylinder was fabricated with thermoplastic polylactic acid (PLA) and an elastomeric thermoplastic polyester elastomer (TPEE). Before this study, these two dramatically different polymers using lattice cylinders had never been compared in a single study. Material extrusion (MEX) 3D-printing was used for manufacturing. Static compression tests, combined with digital image correlation (DIC), were utilized to analyze compression characteristics and deformation modes, and the results were validated through finite element method (FEM) analysis. From the results, due to the same lattice structure, the cylinders of both polymers exhibited similar densification strains as PLA and TPEE, 52.7% and 53.9%, respectively. Due to material effects, the energy absorption per unit volume (EA) of the two lattice cylinder structures is 200.90 and 3260 kJ/m3, respectively. The interlayer adhesion of materials is critical in determining the failure mode and compression behavior of a structure. PLA structural delamination causes the lattice holes to collapse, while TPEE fails due to the collapse of the connection holes. The lattice structure dominates the dynamic elastic recovery (DER) and Tan δ results. [ABSTRACT FROM AUTHOR]

Rock mass deformation and failure are macroscopic manifestations of crack initiation, propagation, and coalescence. However, simulating the transition of rocks from continuous to discontinuous media under cyclic dynamic loading remains challenging. This study proposes a hybrid finite-discrete element method (HFDEM) to model crack propagation, incorporating a frequency-dependent cohesive-zone model. The mechanical properties of standard sandy mudstone under quasi-static and cyclic dynamic loading were simulated using HFDEM, and the method's reliability was verified through experimental comparison. The comparative analysis demonstrates that HFDEM successfully captures crack interaction mechanisms and accurately simulates the overall failure behavior of specimens. Additionally, the effects of pre-existing flaw inclination angle and dynamic loading frequency on rock failure mechanisms were investigated. The numerical results reveal that rock samples exhibit significantly higher compressive strength under dynamic loading compared to quasi-static loading, with compressive strength increasing with higher cyclic dynamic load frequencies. Furthermore, by analyzing the strength characteristics, crack propagation, and failure modes of the samples, insights into the failure mechanisms of rocks under different frequency loads were obtained. This study provides valuable insights into crack development and failure of rocks under seismic loads, offering guidance for engineering practices. [ABSTRACT FROM AUTHOR]

This study focuses on investigating the mechanical behavior of a set of new chemically-treated crosslinked Ultra-High Molecular Weight Polyethylene (UHMWPE) plain-weave fabrics with varying areal densities, and impregnated with a shear thickening fluid (STF). The evaluation of the materials performance included tensile, bias-extension (shear), puncture, and drop tower tests under low rates of loading. For comparison purposes, three different sample groups were considered: untreated fabrics, crosslinked fabrics, and crosslinked fabrics with STF. The STF impregnation was composed of fumed silica nanoparticles (NPs) suspended in a polyethylene glycol (PEG) medium. Both the individual and combined effects of the chemical crosslinking and STF impregnation on the UHMWPE fabrics were explored. Additionally, the impact of strain rate on the tensile and shear behavior of various material groups was examined. The findings revealed that the addition of the crosslinker and shear thickening fluid significantly improves the puncture resistance of the base UHMWPE fabric, by as high as 92 %. The energy absorption and specific energy absorption of the UHMWPE fabric also increased up to 55 % and 16 %, respectively, with the addition of both STF and crosslinker.

Abstract Digital image processing is used to create an optical extensometer to measure deformation in materials under quasi-static loading. The optical extensometer setup created in the present work is a single camera setup which is a two-dimensional system. The main objective of this work is to create an optical extensometer system by digital image processing to measure the deformation and strain in materials under tensile and compressive loading and to calculate the properties of these materials. Furthermore, the aim is to optimize the parameters used in digital image processing by studying the effect of different parameters on the quality of the digital images and performing statistical analysis in order to attain the best configuration of the camera setup. The setup is implemented by acquiring digital images of the tested specimens simultaneously with the load recorded by the load cell, and user-friendly software is developed to analyze the acquired images and measure deformation and strain. Subsequently, the loads can be inserted, and the mechanical properties of the materials tested can be calculated.

To improve the uncertainty of the deformation sequence of the energy-absorbing structures at the end of the subway vehicles during crushing, this paper adopts the gradient design idea of honeycomb structure size, collapse initiator groove and diaphragm. To this end, this paper proposes a honeycomb-filled gradient energy-absorbing structure (HGES) as an energy absorber. The crashworthiness of HGES under axial crushing was investigated by means of finite element (FE) simulations and quasi-static loading tests. After performing parametric analyses on HGES, it was discovered that the wall thickness and the platform intensity of honeycomb had an evident impact, whereas the diaphragm thickness had a relatively little impact on the crashworthiness of HGES. The HGES is then given a multi-objective optimization to further enhance its crashworthiness. The wall thickness, the platform intensity of honeycomb and diaphragm thickness were utilized as the design parameters, while minimal peak crushing force (PCF) and maximal specific energy absorption (SEA) were set as optimization objectives. Finally, a methodology integrating entropy and the order preference by similarity to an ideal solution (TOPSIS) is employed to find the optimal HGES configuration. The SEA and PCF of optimized HGES are enhanced by 19.81 and 25.28%, respectively, when compared to the baseline.

Sandwich panels are widely used in various industries, including the aerospace industry, where they have long been regarded because of their light-weight and high energy absorption capacity. This research introduces a novel type of sandwich panel whose raw material is widely used in the automotive industry. The materials used for manufacturing the sandwich panels addressed in this research are currently used in the cooling radiator structure for the engine of conventional vehicles. Such a radiator is nothing but a lattice of a set of B-shaped tubes and cooling fins. In this research, the crashworthiness properties of such a lattice are extracted along with various directions (samples A, B, and C). Moreover, the applicability of the considered lattices as the core of sandwich panels was studied. This research showed that the considered structures tend to exhibit maximum strength when the loading plane is parallel to the cooling fins. It was further figured out that the addition of aluminum shells to specimens A, B, and C can increase their energy absorption capacity by 85, 268, and 13%, respectively. [ABSTRACT FROM AUTHOR]

A novel quasi-brittle damage model implemented under quasistatic loading condition using bond-based peridynamics theory for progressive failure is proposed to better predict damage initiation and propagation in solid materials. Since peridynamics equation of motion was invented in dynamic configuration, this paper applies the adaptive dynamic relaxation equation to achieve steady-state in peridynamics formulation. To accurately characterise the progressive failure process in cohesive materials, we incorporate the dynamic equation with the novel damage model for quasi-brittle materials. Computational examples of 2D compressive and tensile problems using the proposed model are presented. This paper presents advancement by incorporating the adaptive dynamic equation approach into a new damage model for quasi-brittle materials. This amalgamation allows for a more accurate representation of the behavior of damaged materials, particularly in static or quasi-static loading situations, bringing the framework closer to reality. This research paves the way for the peridynamics formulation to be employed for a far broader class of loading condition behaviour than it is now able to.

To improve the uncertainty of the deformation sequence of the energy-absorbing structures at the end of the subway vehicles during crushing, this paper adopts the gradient design idea of honeycomb structure size, collapse initiator groove and diaphragm. To this end, this paper proposes a honeycomb-filled gradient energy-absorbing structure (HGES) as an energy absorber. The crashworthiness of HGES under axial crushing was investigated by means of finite element (FE) simulations and quasi-static loading tests. After performing parametric analyses on HGES, it was discovered that the wall thickness and the platform intensity of honeycomb had an evident impact, whereas the diaphragm thickness had a relatively little impact on the crashworthiness of HGES. The HGES is then given a multi-objective optimization to further enhance its crashworthiness. The wall thickness, the platform intensity of honeycomb and diaphragm thickness were utilized as the design parameters, while minimal peak crushing force (PCF) and maximal specific energy absorption (SEA) were set as optimization objectives. Finally, a methodology integrating entropy and the order preference by similarity to an ideal solution (TOPSIS) is employed to find the optimal HGES configuration. The SEA and PCF of optimized HGES are enhanced by 19.81 and 25.28%, respectively, when compared to the baseline. [ABSTRACT FROM AUTHOR]

This paper proposes a novel semi-rigid rocking wall-floor connection. To study its seismic behavior, a preliminary study using finite element modeling (FEM) has been conducted to perceive the rocking wall response towards the precast plank before conducting a physical experimental testing in the laboratory. The finite element model was developed to investigate the lateral quasi-static-load response of the isolated rocking wall system. Subsequently, the rocking wall model was further extended by incorporating a precast concrete plank using the proposed connection. The finite element model of the rocking wall showed a good correlation with the analytical model. Furthermore, the study showed that a semi-rigid connection would result in an overstrength that should be considered when designing the rocking wall. [ABSTRACT FROM AUTHOR]

The bending behavior of beams with a square cross-section containing holes under a three-point bending load was investigated in the present study. As aluminum alloys are lighter than steel and there are many automobile companies that use this material, 6063 aluminum alloy was chosen for this study. The present research was carried out both experimentally and numerically. In the numerical section, aluminum beams were simulated with the finite element software LS-DYNA. These beams contained holes with a diameter of 21 mm, which were placed at different distances on the length of the beam. In this research, 36 perforated beams were simulated in three thicknesses: 1, 1.5, and 2, and the holes were placed at 0, 3.5, 7, 10.5, 14, 17.5, 21, 24.5, 28, 35, 42, and 49 mm in relation to the middle of the beam. In addition, a beam without holes was studied for each thickness. Numerical simulations were validated with experiments and good results were observed. The obtained results showed that as the hole moves from the center to the sides, the absorption of energy and maximum force increases. In the final section, the most optimal beams were determined in terms of thickness and hole location, and based on these a car bumper was proposed. [ABSTRACT FROM AUTHOR]

In order to investigate the hysteretic behavior of recycled aggregate concrete with ferronickel slag-filled steel tubular (RAC-FNSFST) columns, the quasi-static loading was implemented on nine specimens with different replacement ratios (RACs), axial load levels, length–diameter ratios, and diameter–thickness ratios. The hysteretic curves, skeleton curves, deformability, energy dissipation capacity, and stiffness degeneration were studied after loading and failure mechanisms were observed, followed by the construction of FE models for parameter analysis. It is demonstrated that the hysteretic loop curve is full, and the hysteretic performance was not dramatically affected by the replacement ratio of RAC. With axial load level increase, ultimate strength at descending stage degrades quickly, stiffness degeneration accelerates, and hysteretic energy dissipation increases. Stiffness degeneration and hysteresis energy dissipation are enhanced as the length–diameter ratio increases. However, when the diameter–thickness ratio decreases, hysteretic energy dissipation increases, and stiffness degeneration accelerates. In addition, a suitable FE model was established and compared with experimental results. Then a wide range of parameter studies was carried out as a supplement to the experimental study. It is shown that the ultimate strength and ductility of specimens are intimately correlated with the RAC strength, yield strength of steel tube, slenderness ratio, axial load level, and steel ratio. [ABSTRACT FROM AUTHOR]

This article investigates the crashworthiness performance of thin-walled glass/epoxy (GFRP) square tubes with cutouts. Specimens were fabricated using wet wrapping process and tested under quasi-static axial compression. Four design variables were selected each at three levels to determine the crashworthiness indicators. The design variables are the hole diameter (6, 12, 18 mm), the hole position (measured from the tube top) to tube length ratio (0.25, 0.5, 0.75), the number of holes and distribution (one hole in one face, two holes in two opposite faces, two holes in two adjacent faces), and crosshead speed (2, 5, 10 mm/min). To find the optimal specimens with the best specific energy absorption (SEA) and the highest crushing force efficiency (CFE), the design of experiments (DOE) using Taguchi approach was employed. A series of experiments based on L9 orthogonal array was conducted. The main effect, signal-to-noise (S/N) ratio, and the analysis of variance (ANOVA) were also performed. The analysis was performed using Minitab 18 Software Package. Results revealed that the hole diameter is the highest influencing parameter on the values of SEA, followed by the crosshead speed with contribution percent of 50.71 and 46.12 %, respectively. The number of holes and distribution is the highest influencing parameter on the values of CFE, followed by crosshead speed, with contribution percent of 40.87 and 32.92 %, respectively. Finally, a confirmation test was performed to verify the optimal test parameters as predicted by Taguchi approach. The optimum SEA and CFE of GFRP tubes with circular cutouts present, respectively, 22.05 and 61.16 % greater than those of intact specimens. [ABSTRACT FROM AUTHOR]

This paper discusses material named Polyurethane bonding which can be used in the stabilization of railroad ballast layer. An experimentation of the static and dynamic response of this material is important in designing appropriate solutions for railroad ballast layer, especially for the transition zone. A comprehensive study on the SHPB testing of Polyurethane bonding is presented in the strain rate range of 1000 s − 1 –4000 s − 1 . Variable power law was used to predict the material response at elevated strain rates as high as 10,000 s − 1 . These results are compared with the material's quasi-static response. The effects of strain rate on material parameters like Young's Modulus and Yield Strength were investigated under various high strain rate dynamic experiments. It was found that the yield strength as well as Young's modulus increased with the strain rate and the trend was more evident at higher strain rates. Quasi-Static Uniaxial Compression tests gave the typical stress–strain relationship of the material. A close investigation of the material response indicates that the behavior of this class of Polyurethane has a close resemblance with PMMA at the quasi-static as well as at various high strain rates. [ABSTRACT FROM AUTHOR]

A cantilever beam with lateral buckled deformation performs bi-stable characteristic. The snapping mechanism between its two stable configurations can be triggered when applying displacement or angle on the free end. In this paper, an analytical model based on the modal superposition method is established to investigate the snap-through behaviour. A spring with stiffness k introduced in the analytical model ensures the quasi-static loading, bringing about the accurate snapping response. In addition, the initial lateral buckling of the cantilever beams and the snap-through behaviour of the lateral buckled beams are simulated using the FE method. The theoretical and numerical results are then validated on specially designed and built apparatus. Geometric parameters analysis indicates that the theoretical model is more accurate in predicating the snapping responses of bi-stable lateral buckled beams with slender features. Understanding the mechanics of snap-through behaviour is important for designing novel lateral buckled beams with target shapes and functions. [ABSTRACT FROM AUTHOR]

The non-unique relationship between the density and quasi-static strength of Miura-ori metamaterials was explored for graded materials with respect to quasi-static and dynamic in-plane compression. A lower bound estimate of quasi-static strength and energy absorption was obtained using an analytical method by only considering the deformation mechanism of the rigid origami motion. Graded origami metamaterials were achieved by applying either a variation of the initial folding angle or a variation of the thicknesses of cell walls in the loading direction. It was shown that grading by a moderate increase of the initial folding angle does not notably contribute to the overall material strength and consequently to an improvement of the energy absorption efficiency of the metamaterial under quasi-static compression. Grading by wall thickness variation leads to a notable strength increase and moderately enhanced energy absorption. It is shown that the significant strength gradient leads to a violation of the rigid motion rule and the cells collapse sequentially, which has been validated by test results published in the literature. Different from quasi-static behavior, the response of the Miura-ori metamaterial to relatively high velocity impact is governed by the density gradient values, regardless of the grading technique. Furthermore, the differently graded profiles (positive or negative) affect the force-displacement histories but not the energy absorption efficiency of the examined metamaterials. [ABSTRACT FROM AUTHOR]

Performance of fiber reinforced Engineered Cementitious Composites (ECC) strengthened by non-ductile Reinforced Concrete (RC) frames with hollow clay brick masonry infill subjected to quasi-static in-plane loading was experimentally assessed herein. The suggested strengthening technique was used for increasing the lateral strength of infilled RC frames and retaining the integrity of the masonry infill wall during earthquake loading. Initially, the mechanical properties of ECC and masonry elements were tested. The ECC was made of water, cement, silica fume (5% of cement weight), Zeolit (5% of cement weight), silica sand, fly ash, superplasticizer, and Poly-Vinil-Alkaol fibers (1.5% of the whole volume of the concrete). Cylinder and Dog-bone specimens were cast and tested to evaluate the compressive and tensile stress-strain behavior of ECC concrete. Afterward, three RC specimens with one-third scale and one bay-single story. Of these specimens, one frame was tested as built without infill (BF) and another frame as built with infill (IF-E0), and the rest of the frames were retrofitted using ECC as an overlay on the masonry wall (IF-DF-E20-1). The infilled frame strengthening using ECC (IF-DF-E20-1) provided lateral strength, stiffness, and energy dissipation capacity of 2.31, 1.11, 1.37 times those of the hollow clay brick masonry infilled frame (IF-E0), respectively. Furthermore, the obtained backbone curves are idealized using a two-line model. The relative displacement of each floor is an important issue in the structural and non-structural seismic designs; thus, the initial cracks (flexural in columns, diagonal in beam-column joint, flexural in beams, cracking in the interface of the frame and infilled bricks, crushing of bricks, shear crack in column, sudden crushing of infill, and concrete crushing of column) at the respected displacement was analyzed here. According to the results, the proposed strengthening technique not only increased the lateral strength and energy absorption capacity of the infilled frame but also provided a reasonable system overstrength and prevented brittle failure modes in the infill wall.

Carbon nanotube fibers or yarns (CNTYs) are lightweight, stiff, strong, electrically, and thermally conductive fiber-like materials that exhibit a piezoresistive response and could be integrated in glass-fiber/epoxy laminated composite materials to measure strain and to detect damage. Aiming at extending the scope of previous studies, this work is about the piezoresistive response of CNTY sensors integrated in composite laminates of industrial interest, accounting for interactions between the CNTY and the typical heterogeneous, anisotropic surrounding media, including the effects induced by the curing process of the composite matrix. This study reports experimental results on the mechanical response of laminated composite materials under quasi-static and vibration loading monitored using integrated CNTY sensors. A combination of CNTY sensor configurations and experimental setups were used to monitor the deformation and strains among the various layers of the laminated composites. As the laminated composites were mechanically loaded under quasi-static four-point bending, the CNTY sensors captured instantaneously the deformation as demonstrated by the change in their electrical resistance. Also, as the laminated composites were subjected to sinusoidal loading at specific frequencies, the integrated CNTY sensors were able to capture the loading cycles exactly including durations and peaks. Integrated sensing using CNTYs may offer a highly adaptive, practical, and sensitive structural monitoring method for a variety of applications. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper investigated the quasi-static and dynamic behavior of 3D auxetic metamaterial structures made from carbon fiber reinforced polymer (CFRP) laminated composite. The aim of the study was to enhance design methodologies for load-bearing and energy absorption applications of these 3D novel structures, filling the research gap in understanding their response to quasi-static and especially dynamic loadings. The two novel 3D structures were designed and fabricated by using an interlocking assembly method based on the 2D auxetic CFRP sheets, which were formed with hybrid double-arrow-head with re-entrant and star unit-cells and made with plain weave carbon epoxy prepregs. The finite element (FE) method was adopted to analyze the mechanical characteristics of the structures under the quasi-static and dynamic loading, and Hashin failure criteria were used to define damage in the structures. The study showed that the designed 3D auxetic CFRP structures simultaneously exhibit superior auxeticity, load-bearing, and energy absorption capacity. [ABSTRACT FROM AUTHOR]

This document is an editorial published in Frontiers in Materials titled "Mechanical properties of advanced materials and structures for energy absorption." The editorial discusses the importance of designing structures and materials that can absorb energy in a controlled and predictable manner. It highlights the advantages of advanced materials and structures, such as their flexibility, energy absorption capacity, and the possibility of utilizing new fabrication methods like 3D-4D printing. The editorial also provides summaries of several research studies that investigate the mechanical properties and performance of different materials and structures for energy absorption. [Extracted from the article]

The present research work is aimed to investigate the effect of infill pattern, density and material types of 3D printed cubes under quasi-static axial compressive loading. The proposed samples were fabricated though 3D printing technique with two different materials, such as 100% polylactic acid (PLA) and 70% vol PLA mixed 30% vol carbon fiber (PLA/CF). Four infill pattern structures such as triangle, rectilinear, line and honeycomb with 20%, 40%, 60%, and 80% infill density were prepared. Subsequently, the quasi-static compression tests were performed on the fabricated 3D printed cubes to examine the effect of infill pattern, infill density and material types on crushing failure behaviour and energy-absorbing characteristics. The results revealed that the honeycomb infill pattern of 3D printed PLA cubic structure showed the best energy-absorbing characteristics compared to the other three infill patterns. From the present research study, it is highlighted that the proposed 3D printed structures with different material type, infill pattern and density have great potential to replace the conventional lightweight structures, which could provide better energy-absorbing characteristics. [ABSTRACT FROM AUTHOR]

This study examined the effect of the upper surface slope and the number of cells in the side beams on the collapse properties using experimental and numerical tests. The numerical studies were conducted with LS-DYNA software, and the accuracy of numerical results was investigated by experimental tests. Using MATLAB software, the second-degree polynomial functions were obtained for the collapse properties of the specimens. Also, after the optimization by the decomposition method, the best mode was introduced for the specimens. The studies on collapse properties showed that increasing the number of cells leads to a decrease in all collapse properties, and increasing the upper surface slope leads to an increase in the collapse properties. Moreover, the optimization results by decomposition method showed that this method could suggest the most optimal model for multi-cell and sloping beams. [ABSTRACT FROM AUTHOR]

In the present research, the influence of cap geometry on the collapse of thin-walled aluminum-made energy absorbers with various section geometries was investigated. For this purpose, a total of 35 different absorbers were subjected to axial quasi-static loading. In this respect, five different section types and seven different cap configurations were considered for the absorbers and their caps, respectively. The analyses were performed in both experimental and numerical methods. The numerical simulations were conducted using LSDYNA Software and experimental tests were performed to verify the numerical investigations. Good agreement was obtained between the experimental data and numerical results. The results indicated that, in all cases, the application of the cap enhanced the crush force efficiency while lowering maximum force at collapse. In the final stage of the research, optimal absorbers for the cases with open-ended and close-ended caps were proposed using Minitab Software based on the response surface methodology.

Steel-concrete-steel (SCS) sandwich panels are composed of two steel plates with low thicknesses and high densities and strengths and one thick layer between both plates with low strength and density known as core that is composed of concrete. Cohesive material-epoxy resin or shear connectors are usually applied in order to connect the plates to the concrete core. SCS sandwich composites are being developed so they can be utilized in offshore structures and buildings. Stud bolt is one of the shear connectors and their interlayer shear behavior is examined in the present study. In order to inspect the effect of parameters on interlayer shear behavior of steel-concrete-steel sandwich structure with stud bolt connectors, push-out test is performed under progressive loading. Pursuant to the tests performed, relations are proposed to predict ultimate shear strength and load-slip behavior of samples with stud bolt shear connectors. Consequently, numerical model of push-out test is presented on the basic component of Steel-Concrete-Steel sandwich structure (SCS) with stud bolt connectors. The results indicated that finite element model is consistent with test results applying mass scaling in Explicit Solver with a suitable analysis speed. Applying the regression analysis on the results of 80 numerical models of push-out test,a relation was proposed for shear strength of push-out samples with stud bolt connectors.

A new modal method for controlling the deformation of a linear elastic structure under conditions of quasi-static loading is proposed. The advantage of the new method is independent control of orthogonal modes, which increases the accuracy and speed of control. To illustrate the proposed method, compensation of the deformation error in a rotary table with a high tilt accuracy is considered. [ABSTRACT FROM AUTHOR]

In this paper the behavior of nested tube systems under quasi-static compressive loading is investigated. Two nested tube systems with metal matrix composite are subjected to compressive loads so that in the system A the exterior and interior tubes are under axial and lateral loads, respectively but in the system B the exterior and interior tubes are under lateral and axial loads, respectively. Furthermore, these systems behavior are studied numerically. The results show that energy absorption capacity for both of nested tube systems is greater than the sum of energy absorption capacities of two constitutive tubes when loaded individually. Also, it is shown that the absorbed energy for system A is greater than that of system B. In this research the effects of section geometry and the condition of loading (axial or lateral)of thinwalled tubes on energy absorption capacity and the value of the peak load are studied both experimentally and numerically. [ABSTRACT FROM AUTHOR]

This paper aims at presenting a thermodynamically consistent elastoplastic fractional time-dependent damage model for describing short- and long-term behaviors of rock-like materials. The model utilizes generalized potential theory with a yield criterion, a non-associated flow rule and an isotropic plastic hardening function for describing the evolution of plasticity. A time-dependent Lemaitre-type damage is introduced through fractional derivative considering the short- and long-term evolution of microstructure, which leads to progressive degradation of elastic modulus and failure strength of material. In this context, both instantaneous and delayed deformations shall be well described within the unique constitutive model. For practical application, an efficient and convergent semi-implicit return mapping (SRM) algorithm involving a plasticity-damage decoupling corrector is developed. The proposed model is finally adopted to predict the mechanical and deformation behavior of several types of rocks under different loading conditions in conventional or quasi-static (different loading strain rate) triaxial compression tests, creep tests and relaxation tests. Comparisons between model predictions and experimental data demonstrate that the proposed model has the capability to reproduce main features of short and long-term behaviors of rock-like materials. [ABSTRACT FROM AUTHOR]

Featured Application: The ballistic modular system was developed to serve as a mobile protective barrier against projectile impact and also to mitigate the effect of secondary fragments and explosions. The advantage of the system lies in its very fast assembly at the point of intervention, where no heavy machinery is needed. The whole system can be assembled just by manual manipulation into various shapes. The system is based on reasonable mobility and versatility of the whole solution, which is achieved by combining basic elements according to the needs of the situation. The static response of ballistic panels and also its resistance to blast and ballistic impact is investigated in the framework of this study. By connecting individual ballistic panels together, the protective barrier can be constructed. The protective barrier can be featured as a system with high mobility and versatility that is achieved by linking basic interlocking plate elements together. The resulting protective barrier can be shaped according to many possible scenarios in a wall with various possible opening angles and a small post with the tetragonal base or a larger post with the hexagonal ground plan. The material solution of the protective barrier benefits from the application of ultra-high-performance fibre-reinforced cement-based composites (UHPFRCC), which meets the requirements for enhanced resistance against extreme loads such as blast or impact. Besides, by using UHPFRCC, thin and slender design can be adopted, which is advantageous in many ways. Slender design results in a lower weight, allowing for easy manipulation and replacement. To verify the behavior of the panels, the proposed barrier was subjected to various loadings at different strain rates. The experimental campaign demonstrated that the protective barrier has a reasonable load-bearing capacity and also sufficient resistance against projectile impact and blast effects. [ABSTRACT FROM AUTHOR]

Lattice structures are widely used in many engineering fields due to their excellent mechanical properties such as high specific strength and high specific energy absorption (SEA) capacity. In this paper, square-cell lattice structures with different lattice orientations are investigated in terms of the deformation modes and the energy absorption (EA) performance. Finite element (FE) simulations of in-plane compression are carried out, and the theoretical models from the energy balance principle are deve-loped for calculating the EA of these lattice structures. Satisfactory agreement is achieved between the FE simulation results and the theoretical results. It indicates that the 30° oriented lattice has the largest EA capacity. Furthermore, inspired by the polycrystal microstructure of metals, novel structures of bi-crystal lattices and quad-crystal lattices are developed through combining multiple singly oriented lattices together. The results of FE simulations of compression indicate that the EA performances of symmetric lattice bi-crystals and quad-crystals are better than those of the identical lattice polycrystal counterparts. This work confirms the feasibility of designing superior energy absorbers with architected meso-structures from the inspiration of metallurgical concepts and microstructures. [ABSTRACT FROM AUTHOR]