Quasi-static Compressive Loading Research Articles

Structural response of the U-type corrugated core sandwich panel used in ship structures under the lateral quasi-static compression load

This paper addresses a study on the structural deformation mechanism of the U-type corrugated core sandwich panel used in ship structures under the lateral quasi-static compression load through the experimental, numerical and analytical methods. Based on the results from quasi-static experiment and the finite element simulation, the deformation characteristics of the U-type corrugated core sandwich panel under the lateral quasi-static compression load are analyzed. The results show that the deformation of the U-type corrugated core sandwich panel can be divided into two processes according to whether the core is in contact during the compression process. And the deformation process has little influence on the variation trend of the structural resistance curve. Based on this, the deformation mode of the U-type corrugated sandwich panel is summarized, and the analytical formula of the deformation resistance of the U-type corrugated core sandwich panel is developed. It is shown that the proposed theoretical deformation model can reflect the main deformation process, and the analytical results match well with the experimental and numerical results.

Effect of temperature and strain rate on the formation of shear bands in polymers under quasi-static and dynamic compressive loadings: Proposed constitutive model and numerical validation

The mechanical behaviour of polymers is strongly influenced by temperature and strain rate conditions. Their effects are clearly observed in the Young modulus and Yield strength assessment. In some cases, a change in material failure mode can be noted, which can be both ductile and brittle. For polymers exhibiting shear bands during compression loading, test conditions may enhance or diminish this effect. In this study, isotactic Polypropylene has been considered due to its strong sensitivity to test conditions; with some combinations of strain rate and temperature, the material is able to undergo large compression with nearly uniform strain distribution, whereas significant shear bands can be observed with other strain rate and temperature combinations. This paper proposes a constitutive law for the mechanical characterization of polymers that show shear banding in compression loading. The proposed law extends a visco-plastic model present in literature, allowing to predict the onset or not of micro-shear banding compression instability. The dependence of constitutive parameters with test conditions is determined by applying the Ree-Eyring equation. The model parameters have been calibrated analytically according to experimental data obtained from compression tests performed in a wide range of strain rates (10−3 to 103 1/s) and temperatures (253–313 K). In addition, the constitutive model has been implemented in a commercial FEM code by means of a user-defined subroutine. Results show a good correspondence between experimental observations and numerical calculations, regarding both stress-strain relationship and shear band formation.

The Mechanical Behavior of Polyline Crease Origami Self-Locking Structure under Quasi-Static Compressive Loading

The unique mechanical behavior of polyline crease (PLC) origami structures inspired by the Tachi-Miura polyhedron (TMP) is investigated. We explore the potential usage as mechanical metamaterials that exhibit negative Poisson’s ratio, self-locking mechanism, and load capacity simultaneously. Poisson’s ratio, locked folding ratio, dimensionless force and folding ratio relationship, and elastic-plastic response during its compressive process (rigid folding motion or plastic bending/buckling) are investigated analytically and experimentally, respectively. The effect of original folding angle and the length-to-height ratio on negative Poisson’s ratio, locked folding ratio, dimensionless force, deformation modes, and the mean compression force are also considered. Based on the experiments, an approximate theoretical study has also been conducted, which shows a reasonable correlation with the experimental results. The results are significant to guide the engineering applications of PLC self-locking origami structures.

Crushing behavior and energy absorption of a bio-inspired bi-directional corrugated lattice under quasi-static compression load

The dactyls of Odontodactylus scyllarus have been proved to be an exceptionally damage-tolerant natural material that can readily smash mollusk shells, crab exoskeletons or other hard-shelled preys. In the present study, inspired by the microstructural features of the impact region in the dactyl of Odontodactylus scyllarus, a novel lightweight bi-directionally corrugated lattice was designed and manufactured by additive manufacturing technology to enhance impact energy absorption capacity. The quasi-static compressive properties and energy absorption behavior of the bi-directionally corrugated lattices were investigated experimentally. The compression responses were simulated by finite element (FE) models to duplicate the deformation process. A parametric analysis based on the validated FE model was conducted to study the effects of wave number, wave amplitude and relative density on collapse mode and energy absorption characteristic of the corrugated lattice structures. The collapse process of the bi-directional corrugated lattices can be mainly classified into three representative failure modes, including the full-folded mode, the global buckling mode and the transitional mode. It was found that the specific energy absorption of the corrugated lattice has a strong connection with the three representative collapse modes. With the same relative density, the lattices collapsed with a transitional mode have better energy absorption than those collapsed with a global buckling mode. Due to the higher energy absorption capacity and crushing force efficiency, the corrugated structures collapsed with a transitional mode are more efficient and suitable to act as an energy absorber than those collapsed with the other collapse modes.

Effect of layering layout on the energy absorbance of bamboo-inspired tubular composites

Gradient distribution of vascular structure made the bamboo wall structure so effective which improved the load-bearing capacity of such bio-mimicked energy absorption structures and modify the crush behavior of thin-walled composite tubes. In this research, the influence of the layering design and stacking sequence on the crush behavior, failure mechanism and absorbed energy of bamboo-inspired GFRP composite tubes is assessed experimentally and numerically. Quasi-static compression tests were conducted to explore seven permutations of Coarse Woven (CW), Fine Woven (FW), and Unidirectional (UD) E/glass fiber sheets, taking into account the longitudinal vascular bundles strengthened by organic matrix. Samples were fabricated employing a modified hand laying up method by using mechanical pressure to obtain better surface finishing and interlaminar adhesion compared to conventional hand layering up methods. To evaluate the corresponding crashworthiness parameters and characterize the crushing behavior of composite tubes, quasi-static axial compressive loading was done. The numerical simulations were validated versus experiments by a commercial finite element (FE) LS-DYNA integrating material model 54. The predicted load-displacement curves and failure mechanisms of FE analysis demonstrate acceptable correlations with visual observations during experimentation. Furthermore, the parametric numerical was performed to examine the effect of different distributions of vascular bundles. The FE analysis results revealed that the crushing behavior of bio-inspired composite tubes depended substantially on layering configuration and the stacking sequence design. The outcomes showed that the combination of woven and unidirectional fibers, respectively, located in the inner layer and hoop direction provide the optimal layering configuration design in terms of crush length efficiency, crush load efficiency, Specific energy absorption, stable progressive crushing, and better manufacturing quality.

Additively Manufactured Stochastic Sheet-Based Cellular Metamaterial: Quasi-Static and High Strain Rate Compressive Loading

Additively Manufactured Stochastic Sheet-Based Cellular Metamaterial: Quasi-Static and High Strain Rate Compressive Loading

Deformation of Molecular Chain's Network Structure of Spherical Gel under Quasi-static Compressive Loading Condition

Elastomeric gels are soft-elastic materials consisting of a three-dimensional crosslinked polymer network and liquid filling the space among such network. To take advantage of the swelling-deformation behavior of elastomeric gel and explore its possibility for applications in engineering as a structural member, investigations on the swelling-deformation behavior under various loading conditions are indispensable. Therefore, in this study, we at first proposed a nonaffine model for the elastomeric gel to account for the change of the entangling structure of polymer chains during the swelling-deformation process, in which the change of the number of polymer chains per unit volume N is depending on the first invariant of right Cauchy-Green deformation tensor I1. And then, to investigate the effect of the nonaffine movement of the polymer chain on the mechanical behavior of the elastomeric gel, we performed a FEM simulation for a spherical gel under quasi-static compressive loading condition. The results show that the swelling-deformation behavior of the spherical gel is quite different at the positions such as the polar, the equator or the center of the sphere.

Parametric design strategy of a novel self-similar hierarchical honeycomb for multi-stage energy absorption demand

The center-vertex honeycomb (CVH) structure based on the self-similar hierarchical evolution of the hexagonal honeycomb (HH) is introduced in this paper. The CVH structure has stable deformation modes, excellent energy absorption performance, and multi-platform features, and can be applied to multi-stage energy absorption devices with special requirements, such as energy-absorbing components of vehicles and trains. In this study, the multi-stage energy absorption characteristics of CVH under the in-plane quasi-static compression load are investigated numerically and theoretically, which is verified by the experimental test. The representative unit cell (RVE) of CVH is divided into three sub-regions with independent thickness parameters according to the position of the hexagon. The effects of different thickness distributions on the performance of CVH are investigated to explore the conditions for the emergence of dual-platform features. Then, the four key design parameters of the whole energy absorption process are extracted, which are derived theoretically based on the stable deformation modes. Further, a detailed parametric design strategy of the CVH specimen is proposed based on the specific engineering requirements. The design results proved that the proposed design strategy is reliable and accurate, which provides valuable suggestions and guidelines for the regulation of the energy absorption process of relevant structures for specific engineering needs.

Dynamic Response of Electro-Mechanical Properties of Cement-Based Piezoelectric Composites

By employing ordinary Portland cement as a matrix and PZT-5H piezoelectric ceramic as the functional body, 1-3 and 2-2 cement-based piezoelectric composites were prepared. Quasi-static compression tests were performed along with dynamic impact loading tests to study the electro-mechanical response characteristics of 1-3 and 2-2 cement-based piezoelectric composites. The research results show that both composites exhibit strain rate effects under quasi-static compression and dynamic impact loading since they are strain-rate sensitive materials. The sensitivity of the two composites has a non-linear mutation point: in the quasi-static state, the sensitivity of 1-3 and 2-2 composites is 157 and 169 pC/N, respectively; in the dynamic state, the respective sensitivity is 323 and 296 pC/N. Although the sensitivity difference is not significant, the linear range of the 2-2 composite is 24.8% and 61.3% larger than that of the 1-3 composite under quasi-static compression and dynamic impact loading, respectively. Accordingly, the 2-2 composite exhibits certain advantages as a sensor material, irrespective of whether it is subjected to quasi-static or dynamic loading.

EVALUATION OF STRENGTH PARAMETERS OF POLYMER COMPOSITES USED FOR DENTAL RESTORATION BY THE METHOD OF ACOUSTIC EMISSION

The aim of the study is to create a technique and perform mechanical tests to determine the strength parameters of dental composites from the standpoint of linear fracture mechanics, and using the phenomenon of acoustic emission to determine the origin and development of destruction of light-curing dental composites under quasi-static local compression load. The following hybrid dental composites of domestic and foreign manufacturers were selected for comparison: Latelux (Latus, Ukraine), TETRIC N-CERAM (Ivoclar Vivadent, Liechtenstein), CHARISMA CLASSIC (Kulzer, Germany). 10 disc samples of 13 mm diameter and 5 mm thick of each material were made by using a specially designed mould for study purposes. Packaging and moulding of the material into the mould was performed in laboratory conditions at an air temperature of 18 – 21°C. Before testing, the samples were kept for 24 hours at a temperature of 37°C in saline solution. The samples were loaded on the SVR-5 machine using a ball indenter. During the experiments, acoustic emission data were simultaneously recorded using the SKOP-8 measuring system. In the post-processing stage, the dependencies of the load change during the experiment, the distribution of the amplitudes of the registered AE signals and their sum over time were recorded. The fracture load, indenter displacement, and the features of composite fracture were determined from the obtained dependencies based on the analysis of AE generation under the load. Analysis of the parameters of the AE signals showed that during the destruction of the Tetric N-Ceram composite the signals had the largest amplitude and energy, and of Latelux had the smallest ones.

Tension-Compression Fatigue Induced Stress Concentrations in Woven Composite Laminate

Tension-compression (T-C) fatigue response is one of the important design criteria for carbon-fibre-reinforced polymer (CFRP) material, as well as stress concentration. Hence, the objective of the current study is to investigate and quantify the stress concentration in CFRP dog-bone specimens due to T-C quasi-static and fatigue loadings (with anti-buckling fixtures). Dog-bone specimens with a [(0/90),(45/−45)4]s layup were fabricated using woven CFRP prepregs and their low-cycle fatigue behaviour was studied at two stress ratios (−0.1 & −0.5) and two frequencies (3 Hz & 5 Hz). During testing, strain gauges were mounted at the centre and edge regions of the dog-bone specimens to obtain accurate, real-time strain measurements. The corresponding stresses were calculated using Young’s moduli. The stress concentration at the specimen edges, due to quasi-static tension, was significant compared to quasi-static compression loads. Furthermore, the stress concentration increased with the quasi-static loading within the elastic limit. Similarly, the stress concentration at the specimen edges, due to tensile fatigue loads, was more significant and consistent than due to compressive fatigue loads. Finally, the effects of the stress ratio and loading frequency on the stress concentration were noted to be negligible.

An Experimental Study of the Cyclic Compression after Impact Behavior of CFRP Composites

The behavior of impact damaged composite laminates under cyclic load is crucial to achieve a damage tolerant design of composite structures. A sufficient residual strength has to be ensured throughout the entire structural service life. In this study, a set of 27 impacted coupon specimens is subjected to quasi-static and cyclic compression load. After long intervals without detectable damage growth, the specimens fail through the sudden lateral propagation of delamination and fiber kink bands within few load cycles. Ultrasonic inspections were used to reveal the damage size after certain cycle intervals. Through continuous dent depth measurements during the cyclic tests, the evolution of the dent visibility was monitored. These measurements revealed a relaxation of the indentation of up to 90% before ultimate failure occurs. Due to the distinct relaxation and the short growth interval before ultimate failure, this study confirms the no-growth design approach as the preferred method to account for the damage tolerance of stiffened, compression-loaded composite laminates.

In-Situ Fracture Tolerance of the Metatarsals During Quasi-Static Compressive Loading of the Human Foot.

Accidental foot injuries including metatarsal fractures commonly result from compressive loading. The ability of personal protective equipment to prevent these traumatic injuries depends on the understanding of metatarsal fracture tolerance. However, the in situ fracture tolerance of the metatarsals under direct compressive loading to the foot's dorsal surface remains unexplored, even though the metatarsals are the most commonly fractured bones in the foot. The goal of this study was to quantify the in situ fracture tolerance of the metatarsals under simulated quasi-static compressive loading. Fresh-frozen cadaveric feet (n = 10) were mounted into a testing apparatus to replicate a natural stance and loaded at the midmetatarsals with a cylindrical bar to simulate a crushing-type injury. A 900 N compressive force was initially applied, followed by 225 N successive load increments. Specimens were examined using X-ray imaging between load increments to assess for the presence of metatarsal fractures. Descriptive statistics were conducted for metatarsal fracture force and deformation. Pearson correlation tests were used to quantify the correlation between fracture force with age and body mass index (BMI). The force and deformation at fracture were 1861 ± 642 N (mean ± standard deviation) and 22.6 ± 3.4 mm, respectively. Fracture force was correlated with donor BMI (r = 0.90). Every fractured specimen experienced a transverse fracture in the second metatarsal. New biomechanical data from this study further quantify the metatarsal fracture risk under compressive loading and will help to improve the development and testing of improved personal protective equipment for the foot to avoid catastrophic injury.

Elastically-isotropic open-cell minimal surface shell lattices with superior stiffness via variable thickness design

Triply periodic minimal surface (TPMS) shell lattices are attracting increasingly attention due to their unique combination of geometric and mechanical properties, and their open-cell topology. However, uniform thickness TPMS shell lattices are usually anisotropic in stiffness, namely having different Young's moduli along different lattice directions. To reduce the elastic anisotropy, we propose a family of variable thickness TPMS shell lattices with isotropic stiffness designed by a strain energy-based optimization algorithm. The optimization results show that all the six selected types of TPMS lattices can be made to achieve isotropic stiffness by varying the shell thickness, among which N14 can maintain over 90% of the Hashin-Shtrikman upper bound of bulk modulus. All the optimized shell lattices exhibit superior stiffness properties and significantly outperform elastically-isotropic truss lattices of equal relative densities. Both uniform and optimized types of N14 shell lattices along [100], [110] and [111] directions are fabricated by the micro laser powder bed fusion techniques with stainless steel 316L and tested under quasi-static compression loads. Experimental results show that the elastic anisotropy of the optimized N14 lattices is reduced compared to that of the uniform ones. Large deformation compression results reveal different failure deformation behaviors along different directions. The [100] direction shows a layer-by-layer plastic buckling failure mode, while the failures along [110] and [111] directions are related to the shear deformation. The optimized N14 lattices possess a reduced anisotropy of plateau stresses and can even attain nearly isotropic energy absorption capacity.

Mechanical characterisation of additively manufactured PA12 lattice structures under quasi-static compression

The primary advantage of lattice structures over other cellular structures is the possibility of obtaining higher mechanical properties combined with lower weight. This paper describes the quasi-static mechanical behaviour of eight lightweight lattice structures of various tessellated unit cell topologies using finite element (FE) analysis. Three types of structures were additively manufactured with polyamide (PA12) material using the advanced Multi Jet Fusion technology and were tested under quasi-static compressive loading. The experimental results were used to validate the FE models of the lattices. We compared specific mechanical properties of all eight structures designed with an identical strut diameter of 1 mm or an identical relative density of 0.095. Such comparisons provide a different order of preference for the lattice structures. Based on Maxwell’s stability criterion, the current eight structures are of bending-dominated nature; however, these structures may exhibit stretch-dominated behaviour due to a reasonable amount of struts aligned in the direction of the external load. An excellent combination of stiffness, strength, and energy absorption can be obtained by the structures, when the load is applied in a specific direction with respect to the strut elements.

3D Microstructure-Based Finite Element Simulation of Cold-Sprayed Al-Al2O3 Composite Coatings Under Quasi-Static Compression and Indentation Loading.

This study developed microstructure-based finite element (FE) models to investigate the behavior of cold-sprayed aluminum–alumina (Al-Al2O3) metal matrix composite (MMC) coatings subject to indentation and quasi-static compression loading. Based on microstructural features (i.e., particle weight fraction, particle size, and porosity) of the MMC coatings, 3D representative volume elements (RVEs) were generated by using Digimat software and then imported into ABAQUS/Explicit. State-of-the-art physics-based modeling approaches were incorporated into the model to account for particle cracking, interface debonding, and ductile failure of the matrix. This allowed for analysis and informing on the deformation and failure responses. The model was validated with experimental results for cold-sprayed Al-34 wt.% Al2O3 and Al-46 wt.% Al2O3 metal matrix composite coatings under quasi-static compression by comparing the stress versus strain histories and observed failure mechanisms (e.g., matrix ductile failure). The results showed that the computational framework is able to capture the response of this cold-sprayed material system under compression and indentation, both qualitatively and quantitatively. The outcomes of this work have implications for extending the model to materials design and for applications involving different types of loading in real-world application (e.g., erosion and fatigue).

An experimental investigation into the quasi-static compression behavior of open-cell aluminum foams focusing on controlling the space holder particle size

In this paper, the metal foams of AA332 and AA1067 alloys were produced using an economical technique called the pressurized infiltration process. The main advantage of this technique is controlling the space holder particle size during the production process which has a considerable effect on the mechanical properties of the foam and higher energy absorption capacity compared to those in the open literature accepted. The mechanical properties of aluminum foams with open-cell morphology under quasi-static compression loading were investigated. The commercial NaCl particles with different particle sizes of 3 mm, 4 mm, and 5 mm were employed as the space holder. To confirm the interconnected open-cell morphology of the foam, X-ray CT-scan images were taken. Moreover, the quasi-static compression behavior of produced foams was studied in terms of the relative density, plateau stress, energy absorption capacity, specific energy absorption, and energy absorption efficiency. The results indicated that increasing the NaCl particle size leads to decreasing all the mentioned parameters except the energy absorption efficiency. Also, compared to open-cell foams produced by AA1067 alloy, using AA332 alloy as the base material leads to improving the mechanical properties of the foam. By using AA332 base material, the average plateau stress of 27.59 MPa, energy absorption capacity of 16.77 MJ/m3, specific energy absorption of 13.43 J/g, and energy absorption efficiency of 73% were achieved at the plateau end strain. • Increasing the space holder size leads to decreasing plateau stress, energy absorption capacity, specific energy absorption parameters. • Increasing the space holder particle size leads to increasing the energy absorption efficiency. • AA332 alloy open-cell foams as the base material leads to improving the mechanical properties of the foam.

Compression properties and impact energy release characteristics of TiZrNbV high-entropy alloy

To explore the potential of high-entropy alloys (HEAs) as energetic structural materials (ESMs), the compression behaviors and impact energy release characteristics of TiZrNbV HEA were investigated. Mechanical experiments at strain rates from 1 × 10−3 s−1 to 1 × 104 s−1 showed that TiZrNbV HEA exhibits clear dynamic brittle fracture behavior under dynamic compression loading, which is diametrically opposite to its behavior under quasi-static compression loading. A Johnson–Cook constitutive model for TiZrNbV HEA was obtained by fitting the experimental data, which demonstrated an apparent strain rate effect. Numerical simulation and microstructure results revealed the role of an adiabatic shear band (ASB) in the brittle fracture. The crack profiles that evolved from the ASB exhibited the typical characteristic for high temperatures. The degree and rate of the chemical reaction and recycled products of direct ballistic tests indicated that severe oxidation reactions induced by the high-temperature profiles resulted in chemical energy release under impact loading. The relationship between the material microstructure and macromechanical behavior of TiZrNbV HEA, which is important in the use of HEAs as ESMs, was revealed in this study through mechanical and material methods and finite element numerical simulation.

Prediction of deformation and failure anisotropy for thin magnesium sheets under mixed-mode loading

The plastic deformation and the failure behavior of a third generation magnesium AZ31 sheet is studied under quasi-static tensile, compressive, and mixed mode loading conditions at room temperature. While the deformation anisotropy is found to be less pronounced compared to previously investigated rolled sheets of this alloy, a strong dependence of the failure strain on the sheets orientation is experienced. This failure anisotropy is further studied and quantified using mixed-mode tests realized using a modified Arcan fixture. The irreversible deformation is modeled in the framework of finite elements using two coupled anisotropic plastic potentials. The model parameters are calibrated using the global force-elongation record of the tested samples. For the prediction of failure, an uncoupled damage model based on transformation of strain rates is developed and applied. It is shown that this model is able to predict the observed edge failure of notched specimens with good accuracy. The model predictions for the smooth tensile tests are analyzed in detail by full-field FE analyses to understand the interaction between strain localization and predicted damage evolution.

Investigation of Compressive Behavior of Pre-folded Thin-walled Column Fabricated by 3D Printing

This paper reveals the mechanical behavior of thin-walled columns with pre-folded patterns subjected to compressive loading. The column specimens (Polylactic Acid) are fabricated using Fused Deposition Modeling 3D printer and subjected to quasi-static compressive loading to investigate their mechanical behavior (by modifying the specimens' cross-section patterns and folding angles). The column specimens are simulated by finite element analysis to understand how the stress distribution and local deformation affecting the stiffness, strength, and overall deformation. The experiments showed that introducing the pre-folded pattern in a thin-walled column with different cross-sections can dramatically lower its structural stiffness (85%) and compressive strength (69%), but increase its deformability (115%), which is good agreement with numerical simulation. The variation of cross-section patterns and pre-folding angle could effectively modify the compressive mechanical behavior. Moreover, the results demonstrate how the FDM 3D Printing method can be used in fabricating a thin-walled column with irregular shapes and then to modify its deformability. This finding can be useful for designing any complex structures requiring specific stiffness and deformation such as suspension devices, prosthetic devices in biomechanics, and robotic structures.