Experimental investigation of initial yield surfaces of solid foams and their evolution under subsequent loading

Felten, Markus; Diebels, Stefan; Jung, Anne

doi:10.1016/j.msea.2020.139762

Cited by 6 publications

(4 citation statements)

References 57 publications

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“…[ 33 ] Nevertheless, the observed minor discrepancy could also arise due the material inherent scattering, which equals about 20% independent of the specimen density as well as the applied complex stress state. [ 9 ] Therefore, the conclusion can be drawn, that no additional strain‐rate effect occurs by applying moderate strain rates as well as the high strain rates, that affects the normalized PCS of open‐cell Ni/PU hybrid metal foams.…”

Section: Resultsmentioning

confidence: 99%

“…In recent years, a novel class of open‐cell Ni/polyurethane (PU) hybrid foams has been increasingly investigated, as the production process via electrochemical deposition enables the precise adjustment of the mechanical properties. [ 9 ] Felten et al [ 10 ] studied potential strain‐rate effects of open‐cell Ni/PU hybrid composite metal foams under low impact velocities up to 550 s −1 using a drop tower setup equipped with a high‐speed camera and an infrared camera. They observed a constant enhancement of 66% for the density normalized PCS under dynamic impact conditions and associated this strain‐rate sensitivity with the microinertia effects described by Calladine and English.…”

Section: Introductionmentioning

confidence: 99%

“…[7] Since the foams have to resist multiaxial static as well as dynamic loads during application, an analysis of potential strain-rate effects under compressive loading is essential. [3,[8][9][10][11] Strain-rate sensitivity in cellular materials is generally known to be based on four main criteria. [4] The first criterion affects exclusively closed-cell foams and open-cell fluid-filled foams, where the pore fluid moves slower in comparison to the surrounding framework.…”

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confidence: 99%

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High Strain‐Rate Compression Experiments on Ni/Polyurethane Hybrid Metal Foams Using the Split‐Hopkinson Pressure Bar Technique

et al. 2021

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Metal foams belong to the class of porous materials. This bio-inspired material class has gained an increasing interest over the last decades as a result of its versatile advantages in the field of lightweight constructions. [1][2][3] Metal foams exhibit a high energy absorption capacity under compression, based on a constant stress level over a large strain regime in the stress-strain curve. Hence, cellular materials are predominantly applied as energy absorbers in packaging, automotive, aerospace, and defence industry. [4] The stress-strain curve under compression loading is divided into three different regions. [5] The first region outlines an elastic deformation in the majority of the struts, nevertheless yielding occurs in isolated struts. Therefore, this region is referred to as pseudoelastic. [6] The end of the pseudoelastic region is achieved as soon as the first pore-layer collapses under the so-called plastic-collapse stress (PCS). Starting from this point, a nearly constant stress plateau emerges, where the remaining pore layers gradually collapse. In this damage stage, distinct flow plateaus emerge on the macroscale. The rising stress at the end of the stress plateau is subsequently generated by an increasing contact among the collapsed struts. This area of densification constitutes hereafter the third region of the stress-strain curve. [2] The particular shape of the stress-strain diagram is moreover based on the specific cellular microstructure of 3D interconnected pores. [7] Since the foams have to resist multiaxial static as well as dynamic loads during application, an analysis of potential strain-rate effects under compressive loading is essential. [3,[8][9][10][11] Strain-rate sensitivity in cellular materials is generally known to be based on four main criteria. [4] The first criterion affects exclusively closed-cell foams and open-cell fluid-filled foams, where the pore fluid moves slower in comparison to the surrounding framework. As a result, the pressure inside the pore rises and strain-rate effects occurs. The second criterion refers to the pore-framework itself. Calladine and English [12] observed microinertia effects in cellular materials depending on the particular deformation mode. While the first deformation mode is dominated by bending and shows no strain-rate sensitivity, the second deformation mode is subdivided into two distinct deformation steps, leading to an overall strain-rate sensitivity. The first step involves a plastic compression of the structure followed by a time-delayed rotation at the plastic flow hinges. [13] Thus, this effect does only depend on the structure of the specimen, however, the third criterion includes furthermore the material properties. According to Gibson and Ashby, [14] the strain-rate effects of metal foams are correlated with the properties of the strut material itself. The last criterion is based on the shock-wave propagation and enhancement, which occur solely for impact velocities above 50 m s À1 . [15] Previously, different results on strain-rat...

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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High Strain‐Rate Compression Experiments on Ni/Polyurethane Hybrid Metal Foams Using the Split‐Hopkinson Pressure Bar Technique

et al. 2021

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“…[16][17][18][19] In the past 20 years, some published references related to the investigation of tensile mechanical properties for PVC foam could be found. 11,16,[20][21][22][23][24][25][26][27][28][29][30][31][32] Gibson and Ashby 4 deeply discussed the tensile fracture behavior of polymer foam materials in their classic works, and proposed a theoretical model to predict the tensile strength of foam with the relative density. Colloca 11 and Walter 25 conducted the quasi-static tensile experiment to characterize the properties (including elastic modulus and strength) of PVC foams with various densities, and found that the material parameters of PVC foams are highly dependent on density.…”

Section: Introductionmentioning

confidence: 99%

Tensile properties of transversely isotropic closed-cell PVC foam under quasi-static and dynamic loadings

Tang,

Li,

Jiang

et al. 2023

Jnl of Sandwich Structures & Materials

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The uniaxial tensile mechanical properties of PVC foam considering the effects of strain rate ([Formula: see text]) and anisotropy ([Formula: see text]) have been investigated by quasi-static and dynamic (Split Hopkinson Tensile Bar, SHTB) tests. Combined high-speed camera system and Digital Image Correlation (DIC) technique, the real-time surface strain field of the specimen during the whole tensile process was obtained. On this basis, the macroscopic response and failure mode of PVC foam were investigated. The failure mechanism of PVC foam under tensile loading was revealed through Scanning Electron Microscope (SEM) images on fracture cross-section of loaded specimen. Finally, based on experimental data, a prediction equation on tensile strength of PVC foam considering the effects of strain rate and loading angle (anisotropy) is proposed. Furthermore, a nonlinear constitutive model is developed to describe the uniaxial tensile mechanical properties of PVC foam.

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Influence of Heat Treatment on Microstructure Evolution and Yield Surfaces of Ni/PU Hybrid Foams

Fries,

Schäfer,

Janka

et al. 2024

Adv Eng Mater

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Metal foams are characterized by low weight, high resource efficiency, high relative stiffness and exceptional energy absorption capacity under compressive load. Nickel/polyurethane (Ni/PU) hybrid foams consist of an open‐cell polyurethane foam coated with a layer of nickel produced by electrochemical deposition. The coating of the polyurethane foams takes place in a flow reactor, in which the electrolyte is pumped through the foam at a defined flow velocity. The macromechanical properties of foam‐like structures depend on the structure of the skeleton, the inherent material properties and, in the case of Ni/PU hybrid foams, the properties of the electrochemically generated nickel layer. To influence their mechanical properties, the Ni/PU hybrid foams are subjected to heat treatment. In the given experimental setup, the parameters flow velocity, temperature and duration of the heat treatment are each investigated at two different levels. Thus, interactions between the initial microstructure and the type of heat treatment are evaluated by means of X‐ray diffraction (XRD) and electron backscatter diffraction (EBSD) measurements. Interactions between initial mechanical properties and heat treatment are investigated by uniaxial compression tests and superimposed compression‐torsion tests. The knowledge gained is used to control the macromechanical properties of the hybrid foam.This article is protected by copyright. All rights reserved.

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Experimental investigation of initial yield surfaces of solid foams and their evolution under subsequent loading

Cited by 6 publications

References 57 publications

High Strain‐Rate Compression Experiments on Ni/Polyurethane Hybrid Metal Foams Using the Split‐Hopkinson Pressure Bar Technique

High Strain‐Rate Compression Experiments on Ni/Polyurethane Hybrid Metal Foams Using the Split‐Hopkinson Pressure Bar Technique

Tensile properties of transversely isotropic closed-cell PVC foam under quasi-static and dynamic loadings

Influence of Heat Treatment on Microstructure Evolution and Yield Surfaces of Ni/PU Hybrid Foams

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