Quasi-static Compression Tests Research Articles

Mechanical properties and energy absorption of medium-entropy alloy triply periodic minimal surface cellular structures fabricated via selective laser melting

Triply periodic minimal surfaces (TPMSs) are extensively used as effective tools for the microarchitectural designing of cellular structures. CoCrNi medium-entropy alloy, known for its high strength and high ductility, is an ideal candidate for fabricating TPMS-based structures. However, few studies have focused on this topic. This study investigated the compressive mechanical and energy absorption properties of CoCrNi D-sheet TPMS cellular structures fabricated via selective laser melting (SLM). The surface morphology of the fabricated D-sheet TPMS structure was observed through scanning electron microscopy, and the deformation and failure mechanisms of the structure were analyzed by the quasi-static compression test. The results indicated that the SLM-ed CoCrNi D-sheet TPMS structure exhibited stable collapse mechanisms compared to other metal-based TPMS structures. Meanwhile, the energy absorption characteristics of the modified finite element (FE) model agreed well with the experimental results. Furthermore, the impact of the level constant on the energy absorption performance of the D-sheet TPMS structure was investigated using the FE model. Thus, an optimal D-sheet (OD-sheet) TPMS structure with lower density and higher energy absorption capacity was obtained. Additionally, the Gibson–Ashby prediction model was established to aid in selecting CoCrNi OD-sheet TPMS structures with controlled relative densities for energy absorption applications.

Enhancing the energy absorption capability of auxetic metamaterials through auxetic cells within re-entrant circular units

Re-entrant circular (REC) auxetic metamaterials have garnered significant attention in structural engineering due to their enhanced energy absorption capability and reduced stress concentration compared to traditional re-entrant auxetic configurations. However, there is considerable potential for further enhancing their design to achieve even greater energy absorption capabilities. This study introduces three novel REC auxetic structures (REC-S, REC-Star and REC-Flower) specifically designed to enhance energy absorption capabilities compared to traditional REC configurations. These structures are formed by deploying an S-shaped, a star, and a newly designed auxetic unit-cell (UC) named Flower into the REC framework and fabricated through 3D printing by using fused deposition modeling (FDM) techniques. Their deformation behavior and mechanical performance are assessed through quasi-static compressive experimental tests and finite element analysis (FEA), with good agreement obtained between the two sets of results. Based on the validated FEA, the effects of the geometrical parameters of the structures on specific stiffness (Es), specific energy absorption (SEA), and Poisson's ratio are further investigated. The results show that the newly designed structures outperform the traditional REC structure with equivalent relative densities (∆ρ) and the REC-Flower has the highest SEA for all relative densities, positioning it as a promising candidate for the next generation of REC structures.

Aluminum hierarchical tubular structure inspired by skeletal muscle tissues: Quasi-static and low-velocity impact testing

This paper investigates experimentally and numerically the protective capability of skeletal muscle-inspired hierarchical tubular (MHT) structures made of aluminum under both quasi-static and dynamic impact conditions. In the quasi-static compression tests, structures with higher hierarchical order were more deformable and had lower contact force. Dynamic impact tests were conducted for the first time on MHT specimens of three different hierarchical orders using a drop tower facility. The results indicated a significant reduction in both the maximum and mean contact forces on the protected body when shielded by the second- and third-order MHT structures. This suggested that increasing the hierarchical order of the structure effectively enhanced impact protection capability. Numerical models were developed using ABAQUS/Explicit to accurately reproduce the deformation process and force-time functions of the dynamic impact scenarios. A parametric study found that the impact resistance performance of the MHT structures was robust against various impact velocities and masses.

Experimental and numerical investigation of crashworthiness of multicell metal/CFRP tubes

Metal/CFRP hybrid thin-walled structures combine low-density and high-strength carbon fibre reinforced plastics (CFRP) with low-cost and stable failure form aluminium, which have drawn increasing attention in the transportation industry. A theoretical model was developed to predict the average crushing force of a hybrid multicell under axial compression. The model captures the main energy dissipation mechanism of the hybrid tube under axial compression, and the average crushing force is determined by a quasi-static compression test. The obtained results show that the average crushing force predicted by the theoretical model is in good agreement with the experimental results. However, the geometry size and configuration of multicell thin-walled structures have important effects on crashworthiness. Therefore, it is necessary to study the parametrization of hybrid multicell tubes. First, the simulation model of the multicell tube is established, and quasi-static experiments verify its accuracy. Second, finite element analysis was used to compare the effects of the geometric size of the cell and the multicell structure of different configurations on the energy absorption characteristics. It is clear that with the increase in the thickness of the large aluminium tube, the specific energy absorption (SEA) and crush force efficiency (CFE) both show an upward trend. In addition, with the increase in the ply number of the CFRP tubes, the SEA also shows a minor monotonic increasing trend. Finally, various hybrid tubes with different configurations are designed, and the C-C4-AL tube (the aluminium tube surrounded by four small-size CFRP tubes being placed inside a CFRP tube.) configuration has the most significant energy absorption (EA) and peak crushing force (PCF).

Rotating coupling of chiral identical twins in multimodal Kresling metamaterials for achieving ultra-high energy absorption

Origami structures have been widely applied for various engineering applications due to their extraordinary mechanical properties. However, the relationship between in-plane rotating coupling and energy absorption of these Origami structures is seldom studied previously. The study proposes a design strategy that utilizes identical-twin rotation (i.e. simultaneous rotation with the same chirality) and fraternal-twin rotation (i.e. simultaneous rotation with the opposite chirality) of Kresling metamaterials to achieve multimodal rotation coupling and enhanced energy absorption. Deformation mode and energy absorption properties of 3D-printed Kresling metamaterials have been studied using both quasi-static compression tests and finite element analysis. Furthermore, effects of polygon units and their connections to 2D and 3D arrangements, which generate 4 × 4 arrays and 2 × 2 × 2 arrays, have been investigated to identify the optimized structures for achieving ultra-high energy absorption of chiral Kresling metamaterials. Results showed that rotating coupling of chiral identical twins in multimodal Kresling metamaterials possesses diverse deformation patterns and ultra-high energy absorption. This study provides a novel strategy to optimize structural designs and mechanical properties of the Kresling metamaterials.

Effects of periodic sequential arrangement of subscale miura-foldcore under quasi-static compression

This study presents experimental and numerical investigations on the quasi-static compressive responses of various subscale Miura-foldcore composites. A series of quasi-static compression tests were conducted on standard Miura foldcore specimens fabricated using carbon/epoxy woven fabric prepregs. Representative volume element (RVE) models, incorporating periodic boundary conditions (PBCs), were developed to predict the size-dependent compressive response of subscale Miura foldcores. The effective properties of the carbon/epoxy woven fabric composite used in this study were calculated using the NASA multiscale analysis tool (NASMAT) via two-step homogenization process. The FE model exhibited comparable agreement with experimental results, showcasing variations of less than 7% and 12% in maximum compressive load and compressive stiffness, respectively. The implementation of PBC in the foldcore RVE models improved modeling accuracy by <4%, but drastically increased total computational time (>50%). The periodic pattern of foldcore unit-cells, where two single foldcore unit-cells were placed in parallel or perpendicular, imposed geometric constraints, resulting in small variations in predicted stress and strain distribution contours. The key findings highlighted in this study suggest that a 1 × 1 foldcore unit-cell model without PBC is sufficient to predict accurate quasi-static compressive responses of foldcore composites. This study advances the understanding of subscale Miura-foldcore composites and provides valuable insights into the limitations associated with the use of PBC in foldcore RVE models. The findings also offer a practical guide for fabricating and analyzing traditional Miura folding patterns, promoting a more efficient and accurate approach for optimizing foldcore composite designs considering both structural performance and manufacturability.

Experimental Investigation of Ice Loads on Structures during Quasi-Static Compression Tests

In polar ship hull structural designs, methods based on regulations are considered the most authoritative; however, they tend to be conservative and often exhibit a notable degree of redundancy. This study aims to evaluate the applicability of the empirical formula for ice load assessments by conducting a series of quasi-static indentation tests on scaled hull plates under laboratory-made ice blocks of different scales. The obtained data include ice loads, structural responses, and characteristics of ice pressure distribution. A detailed comparison of various formulas is provided, along with an examination of their differences and errors in comparison to experimental results. The objective of this paper is to offer technical support for ice load forecasting and assessment.

The mechanical characteristics of an aluminum foam winding CFRP composite structure under axial compression

To enhance the energy absorption properties of the energy-absorbing structure, carbon fiber-reinforced polymer (CFRPs) with higher specific energy absorption and porous material aluminum foam with better compressive characteristics were organically combined, and a lighter aluminum foam winding carbon fiber-reinforced polymer structure (CFRP-FA-FW) was designed. Through quasi-static compression testing, the deformation mode and energy absorption properties of CFRP-FA-FW under axial load were examined. The energy absorption and specific energy absorption of CFRP-FA-FW are both increased by 113.55 % and 60.73 %, respectively, compared to the simple composite structure CFRP-FA. Finite element simulation was used for the parametric analysis of the CFRP-FA-FW structure to assess the effects of the relative density of the aluminum foam, the fiber lay-up angle, and the thickness. The results reveal that the change in the relative density of aluminum foam has little impact on the failure deformation mode of CFRP-FA-FW under axial load; the structure has a higher energy absorption capacity and a smoother energy absorption process when the fiber lay-up angle is [0°/90°]ns and [45°]ns; the energy absorption capacity of CFRP-FA-FW is significantly improved by increasing the thickness of the carbon fiber lay-up, and the procedure is also more efficient.

Study on Static Mechanical Properties and Numerical Simulation of Coral Aggregate Seawater Shotcrete with Reasonable Mix Proportion

This study aims to explore the static mechanical characteristics of coral aggregate seawater shotcrete (CASS) using an appropriate mix proportion. The orthogonal experiments consisting of four-factor and three-level were conducted to explore an optimal mix proportion of CASS. On a macro-scale, quasi-static compression and splitting tests of CASS with optimal mix proportion at various curing ages employed a combination of acoustic emission (AE) and digital image correlation (DIC) techniques were carried out using an electro-hydraulic servo-controlled test machine. A comparative analysis of static mechanical properties at different curing ages was conducted between the CASS and ordinary aggregate seawater shotcrete (OASS). On a micro-scale, the numerical specimens based on particle flow code (PFC) were subjected to multi-level microcracks division for quantitive analysis of the failure mechanism of specimens. The results show that the optimal mix proportion of CASS consists of 700 kg/m3 of cementitious materials content, a water–binder ratio of 0.45, a sand ratio of 60%, and a dosage of 8% for the accelerator amount. The tensile failure is the primary failure mechanism under uniaxial compression and Brazilian splitting, and the specimens will be closer to the brittle material with increased curing age. The Brazilian splitting failure caused by the arc-shaped main crack initiates from the loading points and propagates along the loading line to the center. Compared with OASS, the CASS has an approximately equal early and low later strength mainly because of the minerals’ filling or unfilling effect on coral pores. The rate of increase in CASS is swifter during the initial strength phase and decelerates during the subsequent stages of strength development. The failure in CASS is experienced primarily within the cement mortar and bonding surface between the cement mortar and aggregate.

Mechanical performance of interpenetrating phase composites with multi-sheet lattice structures

Interpenetrating phase composites (IPCs), as a novel type of composite material, offer advantages such as lightweight, high strength, and superior energy absorption. This study proposed a multi-sheet lattice structure based on the Gyroid surface, which was initially designed and then fabricated via TC4 laser powder bed fusion (LPBF). Through the infiltration of epoxy resin, a composite material with interpenetrating phases was achieved. Subsequently, the mechanical properties of the IPCs were comprehensively investigated using experimental and numerical simulation methods. In quasi-static compression tests, the IPCs demonstrated higher strength and improved energy absorption characteristics compared to original lattice structures. However, under dynamic loading conditions, while the strength of the IPCs showed significant enhancement, the improvement in energy absorption characteristics of the composite structures was constrained by temperature rise, thermal softening effects, and the glass transition of the epoxy resin induced by elevated temperatures. Thus, while the proposed IPCs exhibited high strength under both quasi-static and dynamic loads, it is imperative to consider material properties and the influence of temperature on energy absorption to prevent overestimation of performance under dynamic loading conditions. Therefore, this study not only highlights the novelty of utilizing a multi-sheet lattice structure based on the Gyroid surface for creating IPCs, but also underscores the importance of carefully considering temperature effects on material properties when evaluating their performance under dynamic conditions.

Development of predictive model for compressive strength of eco-brick masonry walls using numerical method

The usage of waste plastics in the form of eco-bricks for the construction of buildings is gradually gaining traction. However, the performance of eco-brick masonry walls is not sufficiently known, and the process of setting up experimental rigs for the conduct of compressive strength test of masonry are usually cumbersome and expensive. This study investigated the compressive strength performance of eco-brick masonry walls and developed a predictive model for evaluating the strength of eco-brick masonry walls. Waste polyethylene terephthalate (PET) bottles were physically recycled and utilised to manufacture four samples of eco-bricks, strength grades 40.5, 21.02, 13.52 and 3.05 N/mm2 using stone dust, sharp sand and laterite at predetermined moisture contents. The eco-bricks were laid with seven grades of mortar to build 54 eco-brick masonry prisms. A quasi-static compressive loading test was carried out on the masonries, and predictive models were developed using multiple non-linear regression. The study found that eco-brick masonry prisms supported large loads and failed due to the propagation of tensile cracks and debonding of the units. The study also found that the compressive strength of eco-brick masonry is a power function of the compressive strength of eco-bricks and the mortar used for the bonding. It was determined that the mean ratio of the expected to experimental prism strength was 1.002. The mathematical model developed in this study for predicting the strength of eco-brick masonries can significantly evaluate the compressive strength of eco-brick masonry.

Uniaxial constitutive models for wood under cyclic compression loads with varying loading orientations

A desirable objective is to develop a unified constitutive model for wood that can effectively capture its uniaxial cyclic compressive behaviors. To achieve this goal, quasi-static cyclic compression tests have been conducted to supplement the limited cyclic experimental data available. Observation of deformation within the cell structure led to the concluded that material failure resulted from the coalescence of shear or tensile microcracks and the rearrangement of cell structures in regions under compressive stress. Based on the experimental results, a secant stiffness degradation-based and an empirical-based unified constitutive model for wood were proposed. Comparison between the predicted and experimental results indicated that the two proposed models could accurately capture the nonlinear characteristics of wood.

Study on the factors affecting the mechanical properties of antler under quasi-static compression.

In the natural environment, antlers have a significant mechanical structure that protects the deer head from injury. In this paper, the mechanical properties of antlers were evaluated through quasi-static compression tests and microstructural observation of samples from antlers, and the relationship between the sampling position, load direction, and microstructure and their mechanical properties were investigated. Compression experiments confirmed that the tines had the strongest mechanical properties, followed by the main beams and finally the brow tines. The mechanical properties of the test specimens subjected to axial compression were higher than those of lateral compression. The axial load test of the longitudinal sample of the tine of the antler has the best mechanical properties. Its specific energy absorption is 51.33 J/g, the peak crushing force is 1.26 kN, and the mean crushing force is 1.47 kN. There are many tubular structures in the transverse sections of antlers, and the distribution of fibers in the vertical direction is laminar with alternating rows forming a helical structure. Tubular structures were found to be prevalent in some of the better biomechanical structures by comparison. Numerical modeling simulations to describe the effect of tubular structures on the mechanical properties of antlers. The simulation results show that the increase in the size of the tubular structure improves its energy absorption within the variation of a 20% increase in the size of the long and short axis. These findings provide a theoretical and experimental basis for the design of energy-absorbing structures. RESEARCH HIGHLIGHTS: In this paper, transverse and longitudinal samples were taken from the main beam, tine, and brow tine of antlers, and axial and lateral compression were carried out, respectively. In this paper, quasi-static compression experiments were carried out on antler samples to study the effects of sampling position, loading direction, and microstructure on antler mechanical properties. By means of microstructure observation and numerical modeling, it is determined that the size of the antler Havel tube has an effect on its mechanical properties.

In-plane crushing behavior and energy absorption of sponge-inspired lattice structures

Novel energy-absorbing structures were a crucial requirement for the structural crashworthiness design in the automotive and aerospace industries. Inspired by the unique double-diagonal reinforced configuration of deep-sea glass sponge, we proposed a bionic lattice structure (BLS) fabricated by additive manufacturing (AM). In-plane quasi-static compression tests and numerical simulations were conducted on BLS with varying wall thicknesses (t), and two distinct deformation modes were observed: layer-by-layer mode with zero Poisson's ratio (ZPR) and uniform deformation mode with negative Poisson's ratio (NPR). The effects of structural parameters on the crushing behavior of BLS were investigated by numerical method. It was found that BLS with wall thickness (t) of 1.2 mm exhibited better energy absorption performance than 0.45 mm, with the energy absorption (EA), specific energy absorption (SEA), and mean crushing force (Pm) increased by 745.0%, 216.5%, and 744.3%, respectively. The change in crushing mode was caused by the ‘+’ shaped joints changing from buckling to rotation, and the crushing behaviors of BLS could be effectively controlled by adjusting unit size and unit number. Finally, theoretical prediction models were developed using simplified super folding element (SSFE) theory to gain deeper insights into crushing behavior and performance of BLS. The present study provided valuable insights into the in-plane crushing and energy absorption capabilities of BLS. Moreover, it highlighted the potential of the double-diagonal reinforcement design in developing innovative energy-absorbing structures.

An integrated cell-to-pack design based on an origami sandwich structure to enhance cooling and mechanical performances of battery packs in electric vehicles

The rapid growth in the energy density of batteries in electric vehicles has led to the need for complex structural components and cooling systems to ensure the safety of the battery pack. However, these inactive materials occupy a significant portion, accounting for at least 35% of the pack's volume. To enhance the volume utilization rate of the battery pack, this paper proposes a novel origami structure with its optimized geometry that enhances thermal and mechanical performances as well as crashworthiness performance. The simulation results of temperature evaluation show that the proposed origami channels for a battery pack can reduce the maximum temperature by more than 2.6 °C at a 5C discharging rate and by over 20 °C under internal short-circuit conditions compared with a flat cooling channel. The experimental results of a quasi-static punch compression test demonstrate the enhanced mechanical properties of the origami channels with a significant increase in peak crushing force and impact energy absorption compared with flat cooling channels.

Enhancing crashworthiness characteristics of modified hexagonal honeycomb structural panels through stretching and bending of ribs

The effects of stretching and bending of concave, convex, and horizontal ribs on the energy absorption characteristics of modified hexagonal honeycomb structural panels are investigated under in-plane quasi-static compression loading conditions. In this regard, five hierarchical modified structural panel configurations were fabricated using polylactic acid material (PLA) via a fused filament 3D printer, ensuring uniform wall thickness in the 1.5–2 mm range. The panels included the regular hexagonal panel (RHP), regular hexagonal panel with concave rib (RHCP), regular hexagonal panel with convex rib (RHXP), regular hexagonal panel with concave and horizontal ribs (RHCRP), and regular hexagonal panel with convex and horizontal ribs (RHXRP). In-plane quasi-static compressive loading tests were conducted to analyze crush resistance characteristics, and buckling modes of the modified honeycomb panels were examined through experimental and finite element analysis procedures. The result indicates that the specific energy absorption capacity (SEA) of RHXRP is increasing significantly compared to the SEA capacity of other categories of the structures. The changes in failure modes and increased crush energy absorption characteristics of modified RHP with the introduction of concave, convex, and horizontal ribs are elaborated.

Investigating the Impact Behavior of Carbon Fiber/Polymethacrylimide (PMI) Foam Sandwich Composites for Personal Protective Equipment.

To improve the shock resistance of personal protective equipment and reduce casualties due to shock wave accidents, this study prepared four types of carbon fiber/polymethacrylimide (PMI) foam sandwich panels with different face/back layer thicknesses and core layer densities and subjected them to quasi-static compression, low-speed impact, high-speed impact, and non-destructive tests. The mechanical properties and energy absorption capacities of the impact-resistant panels, featuring ceramic/ultra-high molecular-weight polyethylene (UHMWPE) and carbon fiber/PMI foam structures, were evaluated and compared, and the feasibility of using the latter as a raw material for personal impact-resistant equipment was also evaluated. For the PMI sandwich panel with a constant total thickness, increasing the core layer density and face/back layer thickness enhanced the energy absorption capacity, and increased the peak stress of the face layer. Under a constant strain, the energy absorption value of all specimens increased with increasing impact speed. When a 10 kg hammer impacted the specimen surface at a speed of 1.5 m/s, the foam sandwich panels retained better integrity than the ceramic/UHMWPE panel. The results showed that the carbon fiber/PMI foam sandwich panels were suitable for applications that require the flexible movement of the wearer under shock waves, and provide an experimental basis for designing impact-resistant equipment with low weight, high strength, and high energy absorption capacities.

Mechanical Properties and Failure Behavior of Epoxy Rubber Powder Composites Reinforced with Hollow Beads

In this paper, new epoxy resin/rubber powder/hollow beads three-phase composites were prepared by designing the incorporation of fly ash hollow beads with different mass fractions (5%, 10%, 15%, and 20%) as new reinforcing phases into epoxy resin/rubber powder two-phase composites with 5% mass fraction of carbon black rubber powder. Quasi-static compression tests were conducted at room temperature to test the compressive properties of the oxygen resin/rubber powder/hollow beads composites. Calculate the energy absorption properties and energy absorption efficiency of the composites from the compression curves. Fracture characteristics of compressed material specimens with microscopic morphology were observed by scanning electron microscopy. By systematically analyzing the effect of fly ash hollow beads content on the mechanical properties of epoxy resin/rubber powder/hollow beads three-phase composites, it was found that fly ash hollow beads as reinforcing materials can effectively improve the brittleness and yield strength of epoxy resin/rubber powder as well as the energy-absorbing properties and efficiency of the composites. The energy absorption properties of the epoxy resin/rubber powder/hollow beads composites increased and then decreased with the increase in the mass fraction of fly ash hollow beads. In the epoxy resin/rubber powder/hollow beads composites, the most significant performance was observed when the mass fraction of fly ash was 10%.

Mechanical and fracturing characteristics of defected rock-like materials under biaxial compression

Various types of discontinuities have great influences on rock stability in underground excavation, as engineering disasters can be triggered by crack growth from flaws. Motivated by this concern, quasi-static biaxial compression tests are conducted on rock-like cement mortar materials. These tests examine the effect of shape, orientation, and interaction of pre-existing defects, representing natural or preconditioning fractures. Mechanical and fracturing characteristics are analyzed using stress-strain response, acoustic emission (AE), digital image correlation (DIC), and synchrotron X-ray computed tomography (CT) techniques. It could be found that the confinement increases the sample peak stress and restricts the development of cracks in intact samples. In hole samples, cracks initiate from the boundary of the hole, and the application of the confining pressure restricts the tensile cracks originating at the roof and floor of the hole to some extent. The hole-flaw interaction changes stress distribution and cracking behaviours. Cracks initiating from intersected flaw tips with a high inclination angle coalesce with the hole, while parallel independent flaws block the propagation of the cracks initiating from the hole boundary. Besides, it is proved that the integrated analysis framework, coupled with acoustic emission information interpretation, is feasible to accurately investigate fracturing characteristics in samples with complex pre-existing defects. The findings would benefit underground civil and resource-related projects.

Mechanical properties of CoCrFeNiV high-entropy alloys with different Cu element contents under different strain rates

In this study, the alloys used contained Co, Cr, Fe, Ni, and V as the primary elements, while 6%–10% Cu was used as the added element. The high-entropy alloys (HEAs) were made in an electric-arc vacuum furnace from which specimens in the form of cylinders with a 5-mm diameter and 5-mm length were fabricated. An XRD analysis revealed that alloys with 6% and 8% Cu had a single-phase FCC structure, and a weak BCC peak only appeared in the (110) direction in alloys with 10% Cu. A universal testing machine was used for testing at the strain rates of [Formula: see text][Formula: see text]s[Formula: see text], [Formula: see text][Formula: see text]s[Formula: see text], and [Formula: see text][Formula: see text]s[Formula: see text], and the high strain rate was tested using a split Hopkinson pressure bar (SHPB) under strain at 3000[Formula: see text]s[Formula: see text], 4000[Formula: see text]s[Formula: see text], and 5000[Formula: see text]s[Formula: see text], respectively. The specimens did not fracture during the quasi-static compression and dynamic impact tests, which displayed better ductility. The surface of the three alloys had extensive dendrites and non-equiaxed crystal structures. In an EDS composition analysis, the Cr and V elements were more frequently observed in the intergranular region than in the interdendritic region.