scholarly journals A Phenomenological Approach to Study Mechanical Properties of Polymeric Porous Structures Processed Using Supercritical CO2

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 485 ◽  
Author(s):  
Antonio Tabernero ◽  
Lucia Baldino ◽  
Stefano Cardea ◽  
Eva Martín del Valle ◽  
Ernesto Reverchon
Keyword(s):  
Mechanical Properties ◽  
Graphene Oxide ◽  
Cellulose Acetate ◽  
Polymer Network ◽  
Phenomenological Approach ◽  
Porous Structures ◽  
Compression Tests ◽  
Energy Functions ◽  
Realistic Description ◽  
Strain Energy Functions

This work proposes a modeling of the mechanical properties of porous polymers processed by scCO2, using a phenomenological approach. Tensile and compression tests of alginate/gelatin and cellulose acetate/graphene oxide were modeled using three hyperelastic equations, derived from strain energy functions. The proposed hyperelastic equations provide a fair good fit for mechanical behavior of the nanofibrous system alginate/gelatin (deviations lower than 10%); whereas, due to the presence of the solid in the polymer network, a four-parameter model must be used to fit the composite cellulose acetate/graphene oxide behavior. Larger deviations from the experimental data were observed for the system cellulose acetate/graphene oxide because of its microporous structure. A finite element method was, then, proposed to model both systems; it allowed a realistic description of observable displacements and effective stresses. The results indicate that materials processed using scCO2, when submitted to large stresses, do not obey Hooke´s law and must be considered as hyperelastic.

scholarly journals GEOMETRY AND MECHANICAL PROPERTIES OF A 3D-PRINTED TITANIUM MICROSTRUCTURE

2018 ◽  
Vol 15 ◽  
pp. 104-108
Author(s):  
Luboš Řehounek ◽  
Petra Hájková ◽  
Petr Vakrčka ◽  
Aleš Jíra
Keyword(s):  
Mechanical Properties ◽  
3D Printing ◽  
Uniaxial Compression ◽  
Elastic Moduli ◽  
Weight Ratio ◽  
Porous Structures ◽  
Compression Tests ◽  
Local Material ◽  
3D Printed ◽  
Titanium Microstructure

Construction applications sometimes require use of a material other than construction steel or concrete – mainly in cases, where strength to weight ratio needs to be considered. A suitable solution to this problem are structures manufactured using the 3D printing process, as they have a very good strength to weight ratio (i.e.: Ti-6Al-4V – σ<sub>ult</sub> = 900 MPa and ρ = 4500 kg/m<sup>3</sup>). Trabecular structures are porous structures with local material characteristics identical to their commonly manufactured counterparts, but due to their geometry, they have different global mechanical properties and are suited for special applications. We designed and manufactured six variants of these structures and subjected them to uniaxial compression tests, nanoindentation tests and subsequently evaluated their differences and elastic moduli. The values of global moduli E are in the range of 2.55 GPa – 3.55 GPa for all specimens.

Neural Network Based Constitutive Model for Rubber Material

2004 ◽  
Vol 77 (2) ◽  
pp. 257-277 ◽  
Author(s):  
Y. Shen ◽  
K. Chandrashekhara ◽  
W. F. Breig ◽  
L. R. Oliver
Keyword(s):  
Neural Network ◽  
Curve Fitting ◽  
Energy Function ◽  
Strain Energy ◽  
Strain Energy Function ◽  
Phenomenological Approach ◽  
Neural Network Approach ◽  
Energy Functions ◽  
The Neural Network ◽  
Strain Energy Functions

Abstract Rubber hyperelasticity is characterized by a strain energy function. The strain energy functions fall primarily into two categories: one based on statistical thermodynamics, the other based on the phenomenological approach of treating the material as a continuum. This work is focused on the phenomenological approach. To determine the constants in the strain energy function by this method, curve fitting of rubber test data is required. A review of the available strain energy functions based on the phenomenological approach shows that it requires much effort to obtain a curve fitting with good accuracy. To overcome this problem, a novel method of defining rubber strain energy function by Feedforward Backpropagation Neural Network is presented. The calculation of strain energy and its derivatives by neural network is explained in detail. The preparation of the neural network training data from rubber test data is described. Curve fitting results are given to show the effectiveness and accuracy of the neural network approach. A material model based on the neural network approach is implemented and applied to the simulation of V-ribbed belt tracking using the commercial finite element code ABAQUS.

scholarly journals Post-Processing Treatment Impact on Mechanical Properties of SLM Deposited Ti-6Al-4 V Porous Structure for Biomedical Application

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5167
Author(s):  
Eren Pehlivan ◽  
Jan Džugan ◽  
Jaroslav Fojt ◽  
Radek Sedláček ◽  
Sylwia Rzepa ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Porous Structure ◽  
Structural Damage ◽  
Biomedical Application ◽  
Hot Isostatic Pressing ◽  
Minor Effect ◽  
Porous Structures ◽  
Compression Tests ◽  
Strut Thickness ◽  
Surface Etching

Additive manufacturing technologies allow producing a regular three-dimensional mesh of interconnected struts that form an open-cell porous structure. Regular porous structures have been used in the orthopedic industry due to outstanding bone anchoring. The aim of the study was to determine how the postprocessing influences the mechanical properties of porous structures made of titanium alloy CL 41TI ELI. The effect of hot isostatic pressing (HIP) as a method of increasing microstructural integrity was investigated here. The influence of surface etching (SE) technique, which was applied to the porous structure for cleaning unmelted titanium powder particles on the surface of connectors from the inner surfaces of a porous structure, was examined in this study. Mechanical properties were investigated by means of compression tests. The results point out that HIP has a minor effect on the mechanical behavior of considered porous structures. The SE is an effective method to clean the surface of a porous structure, which is very important in the case of biomedical applications when loose powder can cause serious health problems. Another effect of the SE is also the strut thickness reduction. Reducing strut thickness of a porous structure with the surface etching decreases its stiffness to the same extent as predicted by the relative density theoretical model but did not result in structural damage.

Preparation and characterization of porous hydroxyapatite pellets: Effects of calcination and sintering on the porous structure and mechanical properties

2016 ◽  
Vol 230 (6) ◽  
pp. 985-993 ◽  
Author(s):  
Onder Albayrak ◽  
Mehmet Ipekoglu ◽  
Nazim Mahmutyazicioglu ◽  
Mehmet Varmis ◽  
Emrah Kaya ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Sintering Temperature ◽  
Porous Structures ◽  
Compression Tests ◽  
X Ray Diffraction ◽  
Porous Hydroxyapatite ◽  
Urea Content ◽  
Hydroxyapatite Powder ◽  
Density Values

In this study, porous hydroxyapatite structures were produced by using urea particles of 600–850 µm size. Samples with two different urea composition (25 and 50 wt%) were prepared along with samples without any urea content by adding urea to commercially available hydroxyapatite in its as purchased and calcined states. The produced pellets were sintered at 1100 ℃ and 1200 ℃ for 2 h. Compression tests and microhardness measurements were conducted and changes in density values were examined in order to determine the effect of the calcination state of the prior hydroxyapatite powder, the sintering temperature and the amount of urea added. Also X-ray diffraction, Fourier transform infrared, and scanning electron microscopy analyses were conducted to determine the phase stability, functional groups, and pore morphology, respectively. Calcination is found to negatively affect the densification and sinterability of the produced samples, resulting in a decrease of compressive strength and microhardness. With the control of the urea content and sintering temperature uncalcined hydroxyapatite can successfully be used to tailor the density and mechanical properties of the final porous structures.

Impact of graphene/graphene oxide on the mechanical properties of cellulose acetate membrane and promising natural seawater desalination

2019 ◽  
Vol 39 (9) ◽  
pp. 794-804
Author(s):  
Nahla Ismail ◽  
Ayman El-Gendi ◽  
Hisham Essawy ◽  
Lara Nezam El-Din ◽  
Kamal Abed ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Graphene Oxide ◽  
Cellulose Acetate ◽  
Pure Water ◽  
Natural Seawater ◽  
Cellulose Acetate Membrane ◽  
Permeate Flux ◽  
Salt Rejection ◽  
Wide Range ◽  
Simulated Seawater

Abstract New formulations of cellulose acetate (CA) membrane with graphene (G)/graphene oxide (GO) are suggested and investigated in the present work. This study is intended to find a wide range of conditions for fabricating CA membranes in the presence of some additions of graphene (G), and graphene oxide (GO). The membrane is prepared by phase inversion process. Microscopic investigations for graphene (G), graphene oxide (GO), and prepared membrane were performed by high-resolution transmission electron microscope (HRTEM) and scanning electron microscopy (SEM). The mechanical properties of prepared membranes are determined and evaluated. Permeation tests were performed using natural seawater and simulated seawater to check the prepared membrane performance. The results presented that the permeate flux of M25% CA membranes containing 0.01 wt.% G is the highest flux (57–74 l/m2 h) compared with the neat CA membrane, and the 0.01 wt.% GO-based membranes, while the GO-based membranes were comparable as the neat CA membrane at operating pressures (30–35 bar) and with a feed of 35 g/l NaCl solution. The results showed a remarkable salt rejection of simulated seawater of 95%, and natural seawater with a feed from the Mediterranean Sea displayed 90% salt rejection and accepted pure water flux as well.

scholarly journals Lightweight, flexible, and multifunctional anisotropic nanocellulose-based aerogels for CO2 adsorption

Cellulose ◽  
2020 ◽  
Vol 27 (5) ◽  
pp. 2695-2707 ◽  
Author(s):  
Jiayuan Wei ◽  
Shiyu Geng ◽  
Jonas Hedlund ◽  
Kristiina Oksman
Keyword(s):  
Mechanical Properties ◽  
Cellulose Acetate ◽  
Adsorption Capacity ◽  
Energy Use ◽  
Mechanical Performance ◽  
Functional Materials ◽  
Impregnation Method ◽  
Compression Tests ◽  
Breakthrough Experiments ◽  
And Function

AbstractCO2 adsorption is a promising strategy to reduce costs and energy use for CO2 separation. In this study, we developed CO2 adsorbents based on lightweight and flexible cellulose nanofiber aerogels with monolithic structures prepared via freeze-casting, and cellulose acetate or acetylated cellulose nanocrystals (a-CNCs) were introduced into the aerogels as functional materials using an impregnation method to provide CO2 affinity. The microstructure of the adsorbent was examined using scanning electron microscopy, and compression tests were performed to analyze the mechanical properties of the adsorbents. The CO2 adsorption behavior was studied by recording the adsorption isotherms and performing column breakthrough experiments. The samples showed excellent mechanical performance and had a CO2 adsorption capacity of up to 1.14 mmol/g at 101 kPa and 273 K. Compared to the adsorbent which contains cellulose acetate, the one impregnated with a-CNCs had better CO2 adsorption capacity and axial mechanical properties owing to the building of a nanoscale scaffold on the surface of the adsorbent. Although the CO2 adsorption capacity could be improved further, this paper reports a potential CO2 adsorbent that uses all cellulose-based materials, which is beneficial for the environment from both resource and function perspectives. Moreover, the interesting impregnation process provides a new method to attach functional materials to aerogels, which have potential for use in many other applications.

scholarly journals Design and Characterization of Sheet-Based Gyroid Porous Structures with Bioinspired Functional Gradients

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3844
Author(s):  
Yuan Jin ◽  
Haoyu Kong ◽  
Xueyong Zhou ◽  
Guangyong Li ◽  
Jianke Du
Keyword(s):  
Mechanical Properties ◽  
Physical And Mechanical Properties ◽  
Biomechanical Properties ◽  
Potential Method ◽  
Structural Features ◽  
Design Parameters ◽  
Porous Scaffolds ◽  
Porous Structures ◽  
Compression Tests ◽  
Graded Structures

A new type of sheet porous structures with functionally gradients based on triply periodic minimal surfaces (TPMS) is proposed for designing bone scaffolds. The graded structures were generated by constructing branched features with different number of sheets. The design of the structure was formulated mathematically and five types of porous structure with different structural features were used for investigation. The relative density (RD) and surface area to volume (SA/V) ratio of the samples were analyzed using a slice-based approach to confirm their relationships with design parameters. All samples were additively manufactured using selective laser melting (SLM), and their physical morphologies were observed and compared with the designed models. Compression tests were adopted to study the mechanical properties of the proposed structure from the obtained stress–strain curves. The results reveal that the proposed branched-sheet structures could enhance and diversify the physical and mechanical properties, indicating that it is a potential method to tune the biomechanical properties of porous scaffolds for bone tissue engineering (TE).

Constitutive Equations for Isotropic Rubber-Like Materials Using Phenomenological Approach: A Bibliography (1930–2003)

2006 ◽  
Vol 79 (3) ◽  
pp. 489-499 ◽  
Author(s):  
Vahap Vahapoğlu ◽  
Sami Karadeniz
Keyword(s):  
Energy Function ◽  
Constitutive Equations ◽  
Strain Energy ◽  
Isothermal Condition ◽  
Strain Energy Function ◽  
Phenomenological Approach ◽  
Elastic Behavior ◽  
Energy Functions ◽  
Strain Energy Functions

Abstract To describe the elastic behavior of rubber-like materials, numerous specific forms of strain energy functions have been proposed in the literature. This bibliography provides a list of references on the strain energy functions for rubber-like materials on isothermal condition using the phenomenological approach. The published works, either containing the strain energy function proposals or the discussions on such proposals, based upon the phenomenological approach, are classified.

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