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Special Issue "Microstructure-Mechanical Properties Relationship for Porous Materials"

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Porous Materials".

Deadline for manuscript submissions: 30 September 2019

Special Issue Editor

Guest Editor
Dr. Emanoil Linul

Department of Mechanics and Strength of Materials, Politehnica University of Timişoara, Romania
E-Mail
Interests: porous and cellular materials; polymeric foams; metallic foams; syntactic foams; advanced composite materials; experimental characterization; microstructural analysis

Special Issue Information

Dear Colleagues,

It is my pleasure to invite you to submit a manuscript to the forthcoming Special Issue “Microstructure-Mechanical Properties Relationship for Porous Materials” in Materials (Impact Factor 2.654).

The current interest in every field of today’s engineering world is to increase the use of lightweight materials and integrate them into components designs in order to improve the economy efficiency and reduce the structure weight, without affecting other attributes (cost, performance, comfort, safety, etc.). During the last two decades, fully dense solid materials (steel, Al, Cu, polymers etc.) have lost slowly their applicability, while the use of porous materials (metallic foams, polymeric foams, etc.) has experienced a rapid growth, mainly due to their applications as core material in advanced composite structures. Porous materials are a relatively new class of structural and functional materials exhibiting unique mechanical, physical and other properties that make them attractive in a many wide range of critical structural engineering applications. Moreover, these materials have high stiffness-to-weight ratio, high ability to absorb impact energy, exceptional heat transfer ability, good formability, good corrosion resistance and recycling potential that makes them ideal candidates for replacing high density materials.

This Special Issue represents a good opportunity for researchers around the world to disseminate different aspects of their work related to advanced porous materials: Physical and mechanical properties, collapse mechanisms, microstructure, matrix properties, manufacturing routes and their industrial applications. Of particular interest for this Special Issue is the connection between microstructure and effective properties of porous materials. Therefore, research topics focused on developing novel applications, with emphasis on microstructural features are encouraged. Different conventional/non-conventional experimental and numerical approaches are welcome, with a special appreciation for microstructure-properties relationship.

Research articles, review articles and communications are invited for this Special Issue. Publication is subject to the usual conditions set forth by MDPI as publisher of the journal. Details may be found on the journal’s website at www.mdpi.com/journal/materials.

If you need any further information about this Special Issue, please do not hesitate to contact me.

Dr. Emanoil LINUL
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Advanced porous materials
  • Physical and mechanical properties
  • Microstructure-properties relationship
  • Collapse mechanisms
  • Microstructure
  • Manufacturing routes
  • Matrix properties

Published Papers (14 papers)

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Research

Open AccessArticle
Numerical Modeling and Experimental Behavior of Closed-Cell Aluminum Foam Fabricated by the Gas Blowing Method under Compressive Loading
Materials 2019, 12(10), 1582; https://doi.org/10.3390/ma12101582
Received: 16 April 2019 / Revised: 2 May 2019 / Accepted: 7 May 2019 / Published: 15 May 2019
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Abstract
This paper deals with the experimental and numerical study of closed-cell aluminum-based foam under compressive loading. Experimental samples were produced by the gas blowing method. Foam samples had an average cell size of around 1 mm, with sizes in the range 0.5–5 mm, [...] Read more.
This paper deals with the experimental and numerical study of closed-cell aluminum-based foam under compressive loading. Experimental samples were produced by the gas blowing method. Foam samples had an average cell size of around 1 mm, with sizes in the range 0.5–5 mm, and foam density of 0.6 g/cm3. Foam samples were subjected to a uniaxial compression test, at a displacement rate of 0.001 mm/s. Load and stress were monitored as the functions of extension and strain, respectively. For numerical modeling, CT scan images of experimental samples were used to create a volume model. Solid 3D quadratic tetrahedron mesh with TETRA 10-node elements was applied, with isotropic material behavior. A nonlinear static test with an elasto-plastic model was used in the numerical simulation, with von Mises criteria, and strain was kept below 10% by the software. Uniform compressive loading was set up over the top sample surface, in the y-axis direction only. Experimental tests showed that a 90 kN load produced complete failure of the sample, and three zones were exhibited: an elastic region, a rather uniform plateau region (around 23 MPa) and a densification region that started around 35 MPa. Yielding, or collapse stress, was achieved around 20 MPa. The densification region and a rapid rise in stress began at around 52% of sample deformation. The numerical model showed both compressive and tensile stresses within the complex stress field, indicating that shear also had a prominent role. Mainly compressive stresses were exhibited in the zones of the larger cells, whereas tensile stresses occurred in zones with an increased number of small cells and thin cell walls. Full article
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Open AccessArticle
Influence of Porosity on the Mechanical Behavior during Uniaxial Compressive Testing on Voronoi-Based Open-Cell Aluminium Foam
Materials 2019, 12(7), 1041; https://doi.org/10.3390/ma12071041
Received: 17 December 2018 / Revised: 18 March 2019 / Accepted: 25 March 2019 / Published: 29 March 2019
Cited by 1 | PDF Full-text (2674 KB) | HTML Full-text | XML Full-text
Abstract
We have studied an application of the Voronoi tessellation method in the modeling of open-cell aluminium foam under uniaxial compressive loading. The Voronoi code was merged with computer-aided design (CAD) for converting the polyhedral model into an irregular open-cell cellular structure to create [...] Read more.
We have studied an application of the Voronoi tessellation method in the modeling of open-cell aluminium foam under uniaxial compressive loading. The Voronoi code was merged with computer-aided design (CAD) for converting the polyhedral model into an irregular open-cell cellular structure to create porous samples for compression testing simulations. Numerical simulations of the uniaxial compression uniformly over the upper surface of the sample in the z-axis direction at a constant 20 N load was realised. Samples with three different porosities (30%, 60% and 80%) were studied. A nonlinear elasto-plastic material model with perfect plasticity, without hardening, based on the von Mises yield criterion was applied below 10% strain. Corresponding stress–strain curves were observed and the influence of porosity on deformation mechanism was discussed. Samples with higher porosity exhibited significantly higher normal stress under the same load, and increased stress plateaus. An increase of porosity produced an increase of both compressive and tensile stresses and struts exhibited complex stress fields. Voronoi-based modeling was in accordance with experimental results in the literature in the case of the quasi-static condition and linear elastic region (below 1% strain). Further study is necessary to enable the simulation of real dynamic behaviour under all deformation regimes by using the Voronoi tessellation method. Full article
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Open AccessFeature PaperArticle
Influence of Manufacturing Parameters on Mechanical Properties of Porous Materials by Selective Laser Sintering
Materials 2019, 12(6), 871; https://doi.org/10.3390/ma12060871
Received: 9 January 2019 / Revised: 22 February 2019 / Accepted: 11 March 2019 / Published: 15 March 2019
Cited by 1 | PDF Full-text (3175 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a study on the tensile properties of Alumide and polyamide PA2200 standard samples produced by Additive manufacturing (AM) based on selective laser sintering (SLS). Because of the orthogonal trajectories of the laser beam during exposure, different orientations of the samples [...] Read more.
This paper presents a study on the tensile properties of Alumide and polyamide PA2200 standard samples produced by Additive manufacturing (AM) based on selective laser sintering (SLS). Because of the orthogonal trajectories of the laser beam during exposure, different orientations of the samples may lead to different mechanical properties. In order to reveal this process issue, four orientations of the samples in building envelope were investigated. For data reliability, all the other process parameters were constant for each material and every orientation. The tensile tests highlight small differences in elastic properties of the two materials, while significant differences in strength properties and energy absorption were observed. Nevertheless, Young modulus indicates high stiffness of the Alumide comparing to PA2200 samples. The stereo microscopy reveals a brittle fracture site for Alumide and a ductile fracture with longitudinal splitting zones for PA2200. From the orientation point of view, similar properties of samples oriented at 0 and 90 degrees for all investigated mechanical properties were observed. However, tensile strength was less influenced by the sample orientations. Full article
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Open AccessArticle
Size-Dependent Free Vibration and Buckling of Three-Dimensional Graphene Foam Microshells Based on Modified Couple Stress Theory
Materials 2019, 12(5), 729; https://doi.org/10.3390/ma12050729
Received: 22 January 2019 / Revised: 19 February 2019 / Accepted: 27 February 2019 / Published: 2 March 2019
Cited by 1 | PDF Full-text (4226 KB) | HTML Full-text | XML Full-text
Abstract
In this research, the vibration and buckling of three-dimensional graphene foam (3D-GrF) microshells are investigated for the first time. In the microshells, three-dimensional graphene foams can distribute uniformly or non-uniformly through the thickness direction. Based on Love’s thin shell theory and the modified [...] Read more.
In this research, the vibration and buckling of three-dimensional graphene foam (3D-GrF) microshells are investigated for the first time. In the microshells, three-dimensional graphene foams can distribute uniformly or non-uniformly through the thickness direction. Based on Love’s thin shell theory and the modified couple stress theory (MCST), size-dependent governing equations and corresponding boundary conditions are established through Hamilton’s principle. Then, vibration and axial buckling of 3D-GrF microshells are analyzed by employing the Navier method and Galerkin method. Results show that the graphene foam distribution type, size effect, the foam coefficient, the radius-to-thickness ratio, and the length-to-radius ratio play important roles in the mechanical characteristics of 3D-GrF microshells. Full article
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Open AccessArticle
Numerical Simulation of Thermal Conductivity of Foam Glass Based on the Steady-State Method
Materials 2019, 12(1), 54; https://doi.org/10.3390/ma12010054
Received: 28 November 2018 / Revised: 15 December 2018 / Accepted: 19 December 2018 / Published: 24 December 2018
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Abstract
The effects of fly ash, sodium carbonate content, foaming temperature and foaming time on foam glass aperture sizes and their distribution were analyzed by the orthogonal experimental design. Results from the steady-state method showed a normal distribution of the number of apertures with [...] Read more.
The effects of fly ash, sodium carbonate content, foaming temperature and foaming time on foam glass aperture sizes and their distribution were analyzed by the orthogonal experimental design. Results from the steady-state method showed a normal distribution of the number of apertures with change in average aperture, which ranges from 0.1 to 2.0 mm for more than 93% of apertures. For a given porosity, the thermal conductivity decreases with the increase of the aperture size. The apertures in the sample have obvious effects in blocking the heat flow transmission: heat flow is quickly diverted to both sides when encountered with the aperture. When the thickness of the sample is constant, the thermal resistance of the foam glass sample increases with increasing porosity, leading to better thermal insulation. Furthermore, our results suggest that the more evenly distributed and orderly arranged the apertures are in the foam glass material, the larger the thermal resistance of the material and hence, the better the thermal insulation. Full article
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Open AccessArticle
Mechanical and Microstructural Characterization of an AZ91–Activated Carbon Syntactic Foam
Materials 2019, 12(1), 3; https://doi.org/10.3390/ma12010003
Received: 16 November 2018 / Revised: 28 November 2018 / Accepted: 17 December 2018 / Published: 20 December 2018
Cited by 5 | PDF Full-text (1735 KB) | HTML Full-text | XML Full-text
Abstract
In this study, activated carbon (AC) particles were combined with AZ91 alloy to manufacture a magnesium syntactic foam. This novel lightweight foam has a very low density, in the range of 1.12–1.18 gcm−3. The results show that no chemical reaction occurred [...] Read more.
In this study, activated carbon (AC) particles were combined with AZ91 alloy to manufacture a magnesium syntactic foam. This novel lightweight foam has a very low density, in the range of 1.12–1.18 gcm−3. The results show that no chemical reaction occurred between the AZ91 matrix and the activated carbon particles. The mechanical properties of the foam were evaluated under quasi-static compression loading conditions, and showed a consistent trend for the energy absorption of the fabricated AZ91–AC syntactic foams. The deformation mechanism of samples was a brittle fracture mode with the formation of shear bands during the fracture of all samples. Full article
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Open AccessArticle
Anisotropic Compressive Behavior of Functionally Density Graded Aluminum Foam Prepared by Controlled Melt Foaming Process
Materials 2018, 11(12), 2470; https://doi.org/10.3390/ma11122470
Received: 19 November 2018 / Revised: 2 December 2018 / Accepted: 3 December 2018 / Published: 5 December 2018
Cited by 1 | PDF Full-text (7397 KB) | HTML Full-text | XML Full-text
Abstract
Aluminum foams with a functionally graded density have exhibited better impact resistance and a better energy absorbing performance than aluminum foams with a uniform density. Nevertheless, the anisotropic compression behavior caused by the graded density has scarcely been studied. In this paper, a [...] Read more.
Aluminum foams with a functionally graded density have exhibited better impact resistance and a better energy absorbing performance than aluminum foams with a uniform density. Nevertheless, the anisotropic compression behavior caused by the graded density has scarcely been studied. In this paper, a density graded aluminum foam (FG) was prepared by a controlled foaming process. The effect of density anisotropy on the mechanical behavior of FGs was investigated under quasi-static compression and a low-velocity impact. Digital image correlation (DIC) and numerical simulation techniques were used to identify deformation mechanisms at both macro and cell levels. Results show that transverse compression on FGs lead to a higher collapse strength but also to a lower energy absorption, due to the significant decrease in densification strain and plateau stress. The deformation behavior of FGs under longitudinal compression was dominated by the progressive extension of the deformation bands. For FGs under transverse compression, the failure mode of specimens was characterized by multiple randomly distributed deformation bands. Moreover, the transverse compression caused more deformation on cells, through tearing and lateral stretching, because of the high lateral strain level in the specimens. It was concluded that the transverse compression of FGs lead to a lower plateau stress and a lower cell usage, thus resulting in a poorer energy absorption efficient; this constitutes a key factor which should be taken into consideration in structural design. Full article
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Graphical abstract

Open AccessArticle
Determination of the Elasticity Modulus of 3D-Printed Octet-Truss Structures for Use in Porous Prosthesis Implants
Materials 2018, 11(12), 2420; https://doi.org/10.3390/ma11122420
Received: 23 October 2018 / Revised: 26 November 2018 / Accepted: 27 November 2018 / Published: 29 November 2018
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Abstract
In tissue engineering, scaffolds can be obtained by means of 3D printing. Different structures are used in order to reduce the stiffness of the solid material. The present article analyzes the mechanical behavior of octet-truss microstructures. Three different octet structures with strut radii [...] Read more.
In tissue engineering, scaffolds can be obtained by means of 3D printing. Different structures are used in order to reduce the stiffness of the solid material. The present article analyzes the mechanical behavior of octet-truss microstructures. Three different octet structures with strut radii of 0.4, 0.5, and 0.6 mm were studied. The theoretical relative densities corresponding to these structures were 34.7%, 48.3%, and 61.8%, respectively. Two different values for the ratio of height (H) to width (W) were considered, H/W = 2 and H/W = 4. Several specimens of each structure were printed, which had the shape of a square base prism. Compression tests were performed and the elasticity modulus (E) of the octet-truss lattice-structured material was determined, both, experimentally and by means of Finite Element Methods (FEM). The greater the strut radius, the higher the modulus of elasticity and the compressive strength. Better agreement was found between the experimental and the simulated modulus of elasticity results for H/W = 4 than for H/W = 2. The octet-truss lattice can be considered to be a promising structure for printing in the field of tissue engineering. Full article
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Open AccessArticle
Improved Mechanical Properties and Energy Absorption of BCC Lattice Structures with Triply Periodic Minimal Surfaces Fabricated by SLM
Materials 2018, 11(12), 2411; https://doi.org/10.3390/ma11122411
Received: 12 November 2018 / Revised: 23 November 2018 / Accepted: 26 November 2018 / Published: 29 November 2018
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Abstract
The triply periodic minimal surface (TPMS) method is a novel approach for lattice design in a range of fields, such as impact protection and structural lightweighting. In this paper, we used the TPMS formula to rapidly and accurately generate the most common lattice [...] Read more.
The triply periodic minimal surface (TPMS) method is a novel approach for lattice design in a range of fields, such as impact protection and structural lightweighting. In this paper, we used the TPMS formula to rapidly and accurately generate the most common lattice structure, named the body centered cubic (BCC) structure, with certain volume fractions. TPMS-based and computer aided design (CAD) based BCC lattice structures with volume fractions in the range of 10–30% were fabricated by selective laser melting (SLM) technology with Ti–6Al–4V and subjected to compressive tests. The results demonstrated that local geometric features changed the volume and stress distributions, revealing that the TPMS-based samples were superior to the CAD-based ones, with elastic modulus, yield strength and compression strength increasing in the ranges of 18.9–42.2%, 19.2–29.5%, and 2–36.6%, respectively. The failure mechanism of the TPMS-based samples with a high volume fraction changed to brittle failure observed by scanning electron microscope (SEM), as their struts were more affected by the axial force and fractured on struts. It was also found that the TPMS-based samples have a favorable capacity to absorb energy, particularly with a 30% volume fraction, the energy absorbed up to 50% strain was approximately three times higher than that of the CAD-based sample with an equal volume fraction. Furthermore, the theoretic Gibson–Ashby mode was established in order to predict and design the mechanical properties of the lattice structures. In summary, these results can be used to rapidly create BCC lattice structures with superior compressive properties for engineering applications. Full article
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Open AccessArticle
Dynamic Loading of Lattice Structure Made by Selective Laser Melting-Numerical Model with Substitution of Geometrical Imperfections
Materials 2018, 11(11), 2129; https://doi.org/10.3390/ma11112129
Received: 9 October 2018 / Revised: 24 October 2018 / Accepted: 25 October 2018 / Published: 29 October 2018
Cited by 3 | PDF Full-text (6742 KB) | HTML Full-text | XML Full-text
Abstract
Selective laser melting (SLM) is an additive technology that allows for the production of precisely designed complex structures for energy absorbing applications from a wide range of metallic materials. Geometrical imperfections of the SLM fabricated lattice structures, which form one of the many [...] Read more.
Selective laser melting (SLM) is an additive technology that allows for the production of precisely designed complex structures for energy absorbing applications from a wide range of metallic materials. Geometrical imperfections of the SLM fabricated lattice structures, which form one of the many thin struts, can lead to a great difference in prediction of their behavior. This article deals with the prediction of lattice structure mechanical properties under dynamic loading using finite element method (FEA) with inclusion of geometrical imperfections of the SLM process. Such properties are necessary to know especially for the application of SLM fabricated lattice structures in automotive or aerospace industries. Four types of specimens from AlSi10Mg alloy powder material were manufactured using SLM for quasi-static mechanical testing and determination of lattice structure mechanical properties for the FEA material model, for optical measurement of geometrical accuracy, and for low-velocity impact testing using the impact tester with a flat indenter. Geometries of struts with elliptical and circular cross-sections were identified and tested using FEA. The results showed that, in the case of elliptical cross-section, a significantly better match was found (2% error in the Fmax) with the low-velocity impact experiments during the whole deformation process compared to the circular cross-section. The FEA numerical model will be used for future testing of geometry changes and its effect on mechanical properties. Full article
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Open AccessArticle
Fabrication of Porous Al2O3 Ceramics with Submicron-Sized Pores Using a Water-Based Gelcasting Method
Materials 2018, 11(9), 1784; https://doi.org/10.3390/ma11091784
Received: 20 August 2018 / Revised: 16 September 2018 / Accepted: 18 September 2018 / Published: 19 September 2018
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Abstract
The gelcasting method is usually employed to fabricate relatively dense ceramics. In this work, however, porous Al2O3 ceramics with submicron-sized pores were fabricated using the water-based gelcasting method by keeping the Al2O3 content at low levels. By [...] Read more.
The gelcasting method is usually employed to fabricate relatively dense ceramics. In this work, however, porous Al2O3 ceramics with submicron-sized pores were fabricated using the water-based gelcasting method by keeping the Al2O3 content at low levels. By controlling the water content in the ceramic slurries and the sintering temperature of the green samples, the volume fractions and the size characteristics of the pores in the porous Al2O3 can be readily obtained. For the porous Al2O3 ceramics prepared with 30 vol.% Al2O3 content in the slurries, their open porosities were from 38.3% to 47.2%, while their median pore sizes varied from 299.8 nm to 371.9 nm. When there was more Al2O3 content in the slurries (40 vol.% Al2O3), the porous Al2O3 ceramics had open porosities from 37.0% to 46.5%, and median pore sizes from 355.4 nm to 363.1 nm. It was found that a higher sintering temperature and Al2O3 content in the slurries increased the mechanical strength of the porous Al2O3 ceramics. Full article
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Open AccessArticle
Effects of Pore Size on Fatigue Deformation Mechanism of Open-Cell Copper Foam at Low Stress Amplitude
Materials 2018, 11(9), 1639; https://doi.org/10.3390/ma11091639
Received: 22 July 2018 / Revised: 28 August 2018 / Accepted: 3 September 2018 / Published: 6 September 2018
Cited by 2 | PDF Full-text (3348 KB) | HTML Full-text | XML Full-text
Abstract
Axial compression-compression fatigue experiments on open-cell copper foams with different pore size were investigated in this paper. The effects of the strain amplitude on the fatigue properties were studied and found that there is an exponential relationship between the fatigue life and strain [...] Read more.
Axial compression-compression fatigue experiments on open-cell copper foams with different pore size were investigated in this paper. The effects of the strain amplitude on the fatigue properties were studied and found that there is an exponential relationship between the fatigue life and strain amplitude. The experimental results indicate that a smaller pore size is related to a lower fatigue life. The microstructures of failed copper foam tested at low stress amplitude were observed by optical microscope and scanning electron microscopy (SEM), suggests that different pore size related to different fatigue behavior. The fatigue failure mechanism of the open-cell copper foams were compared by experimental research. Full article
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Open AccessArticle
Novel Negative Poisson’s Ratio Lattice Structures with Enhanced Stiffness and Energy Absorption Capacity
Materials 2018, 11(7), 1095; https://doi.org/10.3390/ma11071095
Received: 22 May 2018 / Revised: 20 June 2018 / Accepted: 20 June 2018 / Published: 27 June 2018
Cited by 2 | PDF Full-text (8595 KB) | HTML Full-text | XML Full-text
Abstract
The weak stiffness and strength of materials with negative Poisson’s ratio limits their application. In this paper, three types of novel lattices with negative Poisson’s ratio are proposed to improve not only stiffness and strength but also energy absorption capacity by embedding different [...] Read more.
The weak stiffness and strength of materials with negative Poisson’s ratio limits their application. In this paper, three types of novel lattices with negative Poisson’s ratio are proposed to improve not only stiffness and strength but also energy absorption capacity by embedding different ribs into a classic re-entrant structure. Unit cell analyses show these novel lattices have significantly increased Young’s modulus along the loading direction, and Type C can maintain sufficient negative Poisson’s ratio performance compared with the base lattice. In addition, the novel lattices exhibit higher yield stress, plateau stress and densification strain extracted from quasi-static compressive simulation. The lattices are prototyped by laser-based additive manufacturing and tested in quasi-static experiments, which show the experimental data match the numerical results within an error of margin. The work signifies the prospect of lattices with negative Poisson’s ratio in enhancing engineering-applicable structures, and indicates the potential of structural topology optimization in more sophisticated designs. Full article
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Open AccessArticle
Microstructure and Properties of Porous High-N Ni-Free Austenitic Stainless Steel Fabricated by Powder Metallurgical Route
Materials 2018, 11(7), 1058; https://doi.org/10.3390/ma11071058
Received: 3 May 2018 / Revised: 7 June 2018 / Accepted: 9 June 2018 / Published: 22 June 2018
Cited by 3 | PDF Full-text (5142 KB) | HTML Full-text | XML Full-text
Abstract
Porous high-N Ni-free austenitic stainless steel was fabricated by a powder metallurgical route. The microstructure and properties of the prepared porous austenitic stainless steel were studied. Results reveal that the duplex stainless steel transforms into austenitic stainless steel after nitridation sintering for 2 [...] Read more.
Porous high-N Ni-free austenitic stainless steel was fabricated by a powder metallurgical route. The microstructure and properties of the prepared porous austenitic stainless steel were studied. Results reveal that the duplex stainless steel transforms into austenitic stainless steel after nitridation sintering for 2 h. The prepared high-N stainless steel consists of γ-Fe matrix and FCC structured CrN. Worm-shaped and granular-shaped CrN precipitates were observed in the prepared materials. The orientation relationship between CrN and austenite matrix is [011]CrN//[011]γ and (-1-11)CrN//(1-11)γ. Results show that the as-fabricated porous high-nitrogen austenitic stainless steel features a higher mechanical property than common stainless steel foam. Both compressive strength and Young’s modulus decrease with an increase in porosity. The 3D morphology of the prepared porous materials presents good pore connectivity. The prepared porous high-N Ni-free austenitic stainless steel has superior pore connectivity, a good combination of compressive strength and ductility, and low elastic modulus, which makes this porous high-N Ni-free austenitic stainless steel very attractive for metal foam applications. Full article
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