Quasi-static Compressive Loading Research Articles

Study on the Mechanical Behavior of a Dual-Density Hybrid Lattice Structure under Quasi-Static and Dynamic Compressions.

The dual-phase lattice structure composed of the matrix phase (MP) and the reinforcement phase (RP) is a novel hybrid lattice showing excellent energy absorption ability. However, the mechanical behavior of the dual-phase lattice structure under dynamic compression and the enhancement mechanism of the reinforcement phase have not been widely studied with the increase in compression speed. Based on the design requirements of dual-phase lattice materials, this paper combined octet-truss cell structures with different porosities, and the dual-density hybrid lattice specimens were fabricated via the fused deposition modeling technique. Under quasi-static and dynamic compressive loadings, the stress-strain behavior, energy absorption capacity, and deformation mechanism of the dual-density hybrid lattice structure were studied. The results showed that the quasi-static-specific energy absorption of the dual-density hybrid lattice structure was significantly higher than that of the single-density Octet lattice, and with the increase in compression strain rate, the effective specific energy absorption of the dual-density hybrid lattice structure also increased. The deformation mechanism of the dual-density hybrid lattice was also analyzed, and the deformation mode changed from an inclined deformation band to a horizontal deformation band when the strain rate changed from 10-3 s-1 to 100 s-1.

Computational Parametric Analysis of Cellular Solids with the Miura‐Ori Metamaterial Geometry under Quasistatic Compressive Loads

Origami‐based metamaterials have widespread application prospects in various industries including aerospace, automotive, flexible electronics, and civil engineering structures. Among the wide range of origami patterns, the fourfold tessellation known as Miura‐ori is of particular attraction to engineers and designers. More specifically, researchers have proposed different 3D structures and metamaterials based on the geometric characteristics of this classic origami pattern. Herein, a computational modeling approach for the design and evaluation of 3D cellular solids with the Miura‐ori metamaterial geometry which can be of zero or nonzero thicknesses is presented. To this end, first, a range of design alternatives generated based on a numerical parametric model is designed. Next, their mechanical properties and failure behavior under quasistatic axial compressive loads along three perpendicular directions are analyzed. Then, the effects of various geometric parameters on their energy absorption behavior under compression in the most appropriate direction are investigated. The findings of this study provide a basis for future experimental investigations and the potential application of such cellular solids for energy‐absorbing purposes.

Mechanical behaviour of gel-filled additively-manufactured lattice structures under quasi-static compressive loading

The worldwide incidence of traumatic brain injuries (TBIs) is on the rise. Helmets are one of the best technologies available to prevent TBIs from impacts to the head during recreational and occupational activities. The most commonly used material for helmet liners is expanded polystyrene (EPS) foam. However, while EPS can reduce linear accelerations from impacts, it does not perform as well at reducing rotational accelerations which are considered to be the most harmful to brain tissue. Recently, prismatic lattice structures have shown promise in reducing these harmful rotational accelerations. Here, a new structure for energy dissipation applications is presented that is hypothesised to improve the energy dissipation of the prismatic lattice by filling it with a gel. To test this hypothesis, 3D printed prismatic lattices fabricated from PLA, PET-G, and ABS were filled with 5 wt% and 10 wt% agar and tested to failure under quasi-static compression. Compared to the unfilled control group, it was found that PLA lattices filled with 10 wt% agar had the best performance demonstrating a 46.1% increase in energy absorbed and 57.4% increase in displacement to failure. These results demonstrate the superior energy dissipation properties of gel-filled prismatic lattices compared to unfilled prismatic lattices during quasi-static compression.

A novel energy-absorbing composite structure with layers of basalt fiber fabric constraining waste brick particles and foam concrete

To seek a new way of recycling the waste brick, a novel energy-absorbing composite structure, consisting of the top layer of basalt fiber fabric constrained waste brick particles (BFCBP) and the bottom layer of foam concrete, is proposed to realize the purpose of the multi-level protection. First of all, the quasi-static compressive test is conducted on the BFCBP specimens with three different height-to-diameter ratios and the foam concrete specimens with four different densities and three height-to-diameter ratios, and their energy absorption performance is evaluated by the test data. The results show that the height-to-diameter ratio of the BFCBP specimen as well as the density and height-to-diameter ratio of the foam concrete specimen have a significant influence on their failure mode and energy absorption. Then after a reasonable combination of the two layers of BFCBP with a height-to-diameter ratio of 1.0 and foam concrete with a density of 700 kg/m3 and a height-to-diameter ratio of 0.5, the quasi-static and dynamic compressive tests are conducted on the energy-absorbing composite structure, and its deformation process, energy absorption, and load transfer under different compressive velocities are experimentally investigated. The test results show that the composite structure subjected to quasi-static and dynamic compressive loading demonstrates layered compression deformation and two-phase energy absorption characteristics, which implies that the proposed composite structure could provide multi-level protection by its staged energy absorption.

Effect of Ti content on the cell structure and compressive and energy absorption properties of Al3Ti/Al6061 foam composite

Aluminium alloy foams are often used as cushioning parts for automobiles because of their excellent energy absorption properties and lightweight characteristics. Their energy absorption properties mainly depend on the cell structure of the foam, but the cell structure of aluminium alloy foams prepared by the powder metallurgy method is usually difficult to control. In this work, Al3Ti/Al6061 foam composite (AT-FC) was prepared by powder metallurgy using TiH2 as the blowing agent and a mixture of Al6061 and Ti powder as the foaming matrix. The effects of different Ti contents on the cell structure, cell distribution and morphology of AT-FC were focused on, and their mechanical properties under quasi-static compressive loading were investigated. The experimental results showed that different Ti contents could regulate the cell size and improve the cell morphology and distribution, in which AT-FC contains 7.5 wt% Ti had the best cell structure with an average cell size of about 1.56 mm and an average circularity of 0.82. By comparing the compressive yield strength, energy absorption and specific energy absorption of AT-FC with different Ti contents, the AT-FC with 10 wt% Ti had the best compressive yield strength of 8.96 MPa and AT-FC with 7.5 wt% Ti had the best energy absorption of 6.50MJ/m3.

Design and Characterization of 2.5D Nature-Inspired Infill Structures under Out-Plane Quasi-Static Loading Condition

The 2.5D (2.5-dimensional) structures are acquired to enhance safety and lightweight designs with better energy absorption in the aerospace and automobile sectors. Additive manufacturing (AM), which is practical to build suitable components in industrial and transportation applications, may produce these structures more efficiently. The current study aims to improve the 2.5D infilled structures mean crush force (MCF) and energy absorption capabilities. Under compression loading, the proposed novel nature-inspired 2.5D infilled structure is compared to six existing 2.5D geometries that are inspired by nature. These structures are made of cylindrical shells that are filled with various infill configurations and maintained at a consistent volume. Photopolymer resin is used as the material for the structures, which are created using a digital light processing (DLP) method under AM technology. The characterization of the constructed models was done under compressive out-plane quasi-static stress conditions. ANSYS numerical simulations have been carried out to confirm the dependability of experimental data. The impact of supporting ribs and infill designs on crushing behaviour is thoroughly discussed. Mean crush force (MCF) and specific energy absorption (SEA) under quasi-static compression loading are provided to the proposed unique nature-inspired 2.5D infilled structure to significantly boost crushing qualities, axial collapse, and energy absorption behaviours.

Mechanical properties of Al2O3 and Al2O3/Al interpenetrated functional gradient structures by 3D printing and melt infiltration

In this paper, Al2O3 functional gradient structures (FGS) were prepared by digital light processing-based 3D printing, and Al2O3/Al interpenetrated FGS was subsequently obtained by melt infiltrating. The microstructure of Al2O3FGS and Al2O3/Al interpenetrated FGS was studied. And the mechanical properties of Al2O3 FGS and Al2O3/Al interpenetrated FGS under quasi-static compression loading were investigated in detail. Compressive strength, Young’s modulus, and energy absorption of Al2O3 FGS and Al2O3/Al interpenetrated FGS were experimental tested, compared, and discussed. The failure behavior of Al2O3 FGS and Al2O3/Al interpenetrated FGS was analyzed by experiments and FEA. This study provides a novel approach for the fabrication of ceramic FGS and ceramic/metal interpenetrated FGS with high mechanical performance.

Mechanical performances of novel cosine function cell-based metallic lattice structures under quasi-static compressive loading

This study proposes a novel lattice structure named cosine function cell-based (CFCB) lattice, in which cell rods are designed in the shape of cosine function curve. Several quasi-static compression tests are conducted to explore their compression behaviors, and their advantages are explored by comparing with traditional body-centered cubic (BCC) lattice structure. Further, influences of several key parameters on mechanical performances are experimentally investigated for CFCB lattice structures. The experimental results indicate that CFCB lattice structures have distinct superiority in compressive stiffness and strength, and their energy absorption characteristics are more than twice as high as those of BCC lattice structure. Further, it is also found that their cell rod diameter and cosine function period length have larger influences on mechanical performances. Subsequently, association relationship between deformation modes and key parameters is numerically explored for CFCB lattice structures, and a distribution map is plotted for their deformation modes. The numerical results indicate that cell rod diameter is positively associated with their energy absorption characteristics, and negatively correlated with their densification strain. Besides, it is also found that the performance indicators exhibit a reducing trend firstly but increase with further raising period length on the whole. With increasing relative density, their energy absorption characteristics and plateau stress show a general upward trend, while a general downward trend is observed in their densification strain. Finally, based on collapse mechanisms of the typical unit cell, theoretical models are deduced to predict equivalent elastic modulus, Poisson’s ratio and plateau stress for the proposed CFCB lattice structures.

3D-printed bioinspired Al2O3/polyurea dual-phase architecture with high robustness, energy absorption, and cyclic life

Ceramics are attractive for structural components because of their excellent load-bearing capacity. Nevertheless, inferior energy-absorbing ability and poor reliability under common quasi-static and dynamic environments, especially under cyclic loading, extremely limit the popularization of ceramic components. The coupling between cellular structures inspired by the light but strong porous trabeculae and core–shell structure in strong and tough natural materials provides a solution for strengthening the load-bearing capacity, energy absorption ability, and cyclic life of ceramic components. Here, we proposed a bioinspired cellular ceramic structure/polyurea (CCS/polyurea) dual-phase architecture via additive manufacturing and simple infiltration technologies. It was demonstrated that the specific load-bearing capacity and energy-absorbing ability of bioinspired CCS/polyurea dual-phase architecture under quasi-static compressive loading were 2.22 and 50.34 times of CCS, respectively. Significantly, it could be repeatedly loaded at 40.28 and 48.82 MPa for over 120 and 8 cycles, respectively. Furthermore, CCS/polyurea dual-phase architecture performed extraordinary cyclic life under dynamic loading. The cyclic lives of CCS/polyurea dual-phase architecture at impact speeds of ∼ 6 and ∼ 12 m/s reached as high as 11 and 2, respectively. This research provides a credible approach to building ceramic-based materials with extraordinary load-bearing capacity, energy absorption ability, and especially remarkable cyclic life.

Experimental and numerical study on the mechanical behavior of 3D printed re-entrant auxetic structure filled with carbon nanotubes-reinforced polymethylmethacrylate foam

The present study aimed to develop the finite element method to examine the mechanical behavior of 3D printed re-entrant auxetic structure filled with nanoparticle-reinforced foams under in-plane uniaxial quasi-static compressive loading. A multi-scale finite element model of the nanocomposite is created by considering the randomly distributed carbon nanotubes (CNT) in the Polymethylmethacrylate (PMMA) polymer matrix for a specific volume fraction. The interaction between CNT and PMMA foam was simulated using the cohesive zone model (CZM). The effect of the volume fraction of carbon nanotubes and the geometric characteristics of the structure on the performance of these structures is examined. Results from the finite element study are validated by the samples manufactured using 3D printing and experimental testing results. The results show that the addition of carbon nanotubes to the re-entrant auxetic structure avoids the sharp reduction of force after the peak point, while the use of 2 wt.% of carbon nanotubes increases the maximum fracture force up to 75%. Results indicate optimal values for carbon nanotube volume fraction and the thickness of the cell walls, for which energy absorption has the highest value. It is concluded that adding 2 wt.% carbon nanotubes to the PMMA foam increases the energy absorption up to 130%.

Impact loading of additively manufactured metallic stochastic sheet-based cellular material

The mechanical response of additively manufactured sheet-based stochastic cellular materials under impact loading was investigated in this work. Samples with four different relative densities (13%, 16%, 19%, and 21%) were fabricated out of 316 L stainless steel using the powder bed fusion (PBF) additive manufacturing (AM) technique. The samples were then tested under quasi-static and dynamic (impact) compressive loading conditions to evaluate their mechanical behavior. All analyzed samples showed a similar progressive plateau stress behavior at all analyzed strain rates. The Crash Force Efficiency (CFE) values of samples at analyzed strain rates were in the range of 67–70%, indicating the uniformity of their mechanical response, which is a vital application feature. The samples exhibited excellent Specific Energy Absorption (SEA) capacity ranging between 5 and 9.2 J/g in the quasi-static deformation mode while achieving up to 35 J/g in the shock deformation mode. Thus, the proposed design approach has great potential for impact and blast mitigation applications. The first and second critical loading velocities of analyzed samples are proportional to the relative density and are in the range of 25–32 m/s and 43–56 m/s, respectively. Minor strain rate hardening was observed in quasi-static deformation mode, while a significant strain rate hardening was observed in shock deformation mode achieved by powder gun testing. The developed and validated computational models offered a more detailed analysis of the deformation mechanism and provided means to predict the sample's behavior at very high strain rates.

Failure analysis on fully-transparent deep-sea pressure hulls used at 2,500 m depth

Fully-transparent deep-sea pressure hulls have been attracted attention in recent years with the increasing demand for underwater observation. So far, public researches on design rule and failure modes for fully-transparent deep-sea pressure hulls are limited and the relevant experience cannot meet the requirements of new cabin design. In this study, the compression test is carried on, in which the material samples are subjected to quasi-static compressive load until failure in tests at different loading rates, and the hyperelastic finite element model is established in LS-DYNA software to simulate the failure process. Simulation results of material properties in finite element analysis on the cylindrical samples are compared with the experimental data, including the characteristic points of the mechanical properties in elastic stage and hardening stage, the ultimate load and failure mode of the samples. Mesh convergence analysis is conducted, and the appropriate mesh quality is accordingly selected in simulation of fully-transparent deep-sea pressure hulls. An equation for prediction of instability-type failure is described, which is derivation based on the classical analytical expression of elastic instability, thus, when 5 times of safety factor is taken, the wall thickness of the pressure hull is calculated to be t/R0 = 0.0685 at 2,500 m depth. Ultimate strength and failure mode of a typical fully-transparent deep-sea pressure hull are simulated. First, the first-order linear buckling modal analysis is carried out to simulate initial geometric imperfections. Then, simulations for the loading and collapse process of two fully-transparent pressure hulls respectively with one opening and two openings are conducted, and the ultimate load of 126 MPa and 128 MPa for the two kinds of hulls are obtained. Finally, simulation of a scaled pressure hull is carried out and simulation results are compared with the experimental data in reference, which are basically consistent. The calculated failure strength shows that the spherical hulls satisfy the safety factor requirement of 5 times. The provided simulation procedure can be referred for failure analysis of fully-transparent pressure hulls.

Review of mechanical properties and impact response of PLA auxetic structures

In this paper, mechanical properties under quasi-static loading conditions and low to high-velocity impact response of Poly-lactic acid (PLA) material produced by the Fused Deposition Modeling (FDM) 3D printing method, having auxetic and non-auxetic geometric structures are critically assessed. Specifically, the load–displacement curve under various loads and parameters, such as energy absorption and the existence of the NPR effect with varying applied loads, are investigated. The effect of a large collection of material parameters, process parameters, and geometrical effects on load–displacement curves, strength, stiffness, and energy absorption are discussed in detail. The in-depth studies on auxetic structures of PLA, for quasi-static compressive load and low to high-velocity impact load, have shown that its impact resistance is superior to that of its non-auxetic counterparts. Also, a method for predicting peak load and maximum displacement for low-velocity impact derived from quasi-static loading data is discussed.

Decoupling Uniaxial Tensile Prestress and Waveguide Effects From Estimates of the Complex Shear Modulus in a Cylindrical Structure Using Transverse-Polarized Dynamic Elastography.

Dynamic elastography, whether based on magnetic resonance, ultrasound, or optical modalities, attempts to reconstruct quantitative maps of the viscoelastic properties of biological tissue, properties altered by disease and injury, by noninvasively measuring mechanical wave motion in the tissue. Most reconstruction strategies that have been developed neglect boundary conditions, including quasi-static tensile or compressive loading resulting in a nonzero prestress. Significant prestress is inherent to the functional role of some biological tissues currently being studied using elastography, such as skeletal and cardiac muscle, arterial walls, and the cornea. In the present article a configuration, inspired by muscle elastography but generalizable to other applications, is analytically and experimentally studied. A hyperelastic polymer phantom cylinder is statically elongated in the axial direction while its response to transverse-polarized vibratory excitation is measured. We examine the interplay between uniaxial prestress and waveguide effects in this muscle-like tissue phantom using computational finite element simulations and magnetic resonance elastography measurements. Finite deformations caused by prestress coupled with waveguide effects lead to results that are predicted by a coordinate transformation approach that has been previously used to simplify reconstruction of anisotropic properties using elastography. Here, the approach estimates material viscoelastic properties that are independent of the nonhomogeneous prestress conditions without requiring advanced knowledge of those stress conditions.

Mechanical behavior and failure modes of bamboo scrimber under quasi-static and dynamic compressive loads

Bamboo scrimber (BS), a renewable fiber-reinforced composite, is considered an ideal alternative to traditional construction materials. To investigate the compressive mechanical response of BS at different strain rates, experiments were conducted in three directions (directions X, Y, and Z) under quasi-static and dynamic loads. Results indicate that the mechanical properties in direction X are better than the other two. The failure modes in direction X include bulking, shearing and debonding, while shearing and crushing modes occur in directions Y and Z, respectively. Four compression phenomenological constitutive models are summarized via the stress–strain relationship. The strain rate effect represented by a DIF model and the micro-mechanism can be interpreted as micro-inertia and local densification. Compressive strength and Young’s modulus also can be influenced by the size and shape effect.

Comparative study of cross-ply laminated composite materials and effect of buckling response with and without cutouts

In this work, finite element analysis has been done along with experimental test and conducted using numerical and experimental tests of the buckling response of quasi-static compressive loading of six layers woven cross-ply laminated composite material [0º/90º/0º] with centrally square and circular cutouts. The effect of cut-out shape and its size with a buckling load were obtained experimentally and numerically. Compression experiment has been performed by using INSTRON machine, and the experimentally obtained buckling loads are compared with a numerical results obtained by ANSYS simulation program. Both experimental and numerical results are showing good agreement. It is noticed that the buckling load of the composite plate has been decreased with the increasing of the size of cutout. The cutout area, cutout ratio (d/w), fiber weight, plate thickness and fiber type of the plate has a major effect to the load of the cross-ply laminated composite plates.

Lightweight cost-effective hybrid materials for energy absorption applications

The present paper experimentally explores the influence of the fiber hybridization and layering sequence on crashworthiness behavior and deformation history of polymer/metal thin-walled pipes. Jute (J)/glass (G) reinforced epoxy over wrapped aluminum (Al) pipes were prepared via hand wet wrapping then subjected to axial quasi-static compressive loads. The load versus displacement plots and crashing indicators, i.e. peak crushing load ({mathrm{F}}_{mathrm{ip}}), mean crushing load ({mathrm{F}}_{mathrm{m}}), total energy absorption (mathrm{U}), specific energy absorption left(mathrm{SEA}right), and crush force efficiency left(mathrm{CFE}right) were determined. Experimental results revealed that the maximum left(mathrm{SEA}right) was recorded for Al/2J/4G/2J pipe with a value of about 42.92 kJ/g, with an enhancement of 20.56% in left(mathrm{SEA}right) compared with pure Al-pipes. Al/2J/4G/2J specimens display the maximum (mathrm{U}), left(mathrm{SEA}right), and left(mathrm{CFE}right) and could be employed as energy absorbing members in automobiles.

Auxetics and Other Systems with Unusual Characteristics

Auxetics and Other Systems with Unusual Characteristics

Bio-inspired Ti‐6Al‐4V mechanical metamaterials fabricated using selective laser melting process

In the current study, porous architecture of the Euplectella aspergillum has been used to mimic mechanical metamaterial. Modelled metamaterial are fabricated using selective laser melting (SLM) process with Ti-6Al-4V alloy. The fabricated metamaterials are mechanically tested under quasi-static compressive loading condition. The heat treatment effect on compressive behavior and microstructure is also observed. The as-printed metamaterial has strength (173.36 MPa) and fracture strain (2.96%), whereas heat-treatment decreases the strength to (146.08 MPa) and increases the fracture strain to (12.60%). The increase in ductility after heat treatment is due to the formation of β-Ti and decrease in residual stresses. The presence of β-Ti phase is confirmed using microstructural and X-ray diffraction method. X-ray diffraction also confirms the decrease in tensile residual stress value from (179.5 ± 4.5 MPa) for as-printed to (96.5 ± 2.4 MPa) after heat-treatment process. Normal residual stress value is also dependent on the location of measurement on the metamaterial. However, heat treatment and location of measurement have no effect on shear residual stress. In the last, finite element simulation has been carried out to visualize the effect of diagonal struts on the deformation behavior. The result shows diagonal struts in the E. aspergillum based metamaterial helps to prevent global buckling and uniformly distribute the load, hence improves the strength of the metamaterial. • 2D Metamaterials are derived from Euplectella aspergillum • Metamaterials are fabricated using selective laser melting process with Ti-6Al-4V alloy • Mechanical and fracture behavior of the as-printed and heat-treated samples is compared • Bio-inspired metamaterial shows improved buckling resistance properties • Residual stress decreases with heat treatment and it is dependent on the topology

Biaxial Tensile Prestress and Waveguide Effects on Estimates of the Complex Shear Modulus Using Optical-Based Dynamic Elastography in Plate-Like Soft Tissue Phantoms.

Dynamic elastography attempts to reconstruct quantitative maps of the viscoelastic properties of biological tissue, properties altered by disease and injury, by noninvasively measuring mechanical wave motion in the tissue. Most reconstruction strategies that have been developed neglect boundary conditions, including quasi-static tensile or compressive loading resulting in a nonzero prestress. Significant prestress is inherent to the functional role of some biological tissues, such as skeletal and cardiac muscle, arterial walls, and the cornea. In the present article a novel configuration, inspired by corneal elastography but generalizable to other applications, is studied. A polymer phantom layer is statically elongated via an in-plane biaxial normal stress while the phantom's response to transverse vibratory excitation is measured. We examine the interplay between biaxial prestress and waveguide effects in this plate-like tissue phantom. Finite static deformations caused by prestressing coupled with waveguide effects lead to results that are predicted by a novel coordinate transformation approach previously used to simplify reconstruction of anisotropic properties. Here, the approach estimates material viscoelastic properties independent of the nonzero prestress conditions without requiring advanced knowledge of those stress conditions.