Modulus Strain Research Articles

New novel thermal insulation and sound-absorbing materials from discarded facemasks of COVID-19 pandemic

Due to the COVID-19 pandemic, people were encouraged and sometimes required to wear disposable facemasks, which then are discarded creating an environmental problem. In this study, we aim at investigating novel ideas to recycle wasted facemasks in order to lower the environmental impact. An experimental study has been carried out to investigate the possibility of using discarded masks for thermal insulation and sound absorption. The wasted masks are simulated by new masks, which stripped off the nose clips, elastic ear loops and are heated to 120 °C for one hour to kill any biological contaminants. The masks are also melted to investigate their thermal insulation and sound absorption properties. Results show that the thermal conductivity coefficients of the loose and melted masks are 0.03555 and 0.08683 W/m K, respectively, at room temperature of about 25 °C. Results show also that the sound absorption coefficient for loose masks is above 0.6 for the frequency range 600–5000 Hz. The loose facemasks are found to be thermally stable up to 295 °C, elastic ear loops at 304.7 °C, and the composite (melted) facemasks at 330.0 °C using the thermo-gravimetric analysis. Characterization of the facemask’s three-layer fibers and the composite (melted) samples is obtained using scanning electron microscopy (SEM). The three-point bending test is obtained for the composite specimens showing good values of flexural stress, flexural strain, and flexural elastic modulus. These results are promising about using such discarded masks as new thermal insulation and sound-absorbing materials for buildings replacing the synthetic or petrochemical insulation materials.

Statistical modelling of tensile properties of natural fiber yarns considering probability distributions of fiber crimping and effective yarn elastic modulus

Unlike synthetic fiber yarns, due to limited fiber length, natural fiber yarns are made of twisted short natural fibers with various crimping status obeying certain probability distribution. Meanwhile, variations from fiber tensile properties and number of fibers in a yarn also result in scattering of mechanical properties of natural fiber yarns. An analytical model is proposed based on statistic theory to characterize the stochastic tensile properties of natural fiber yarns by defining crimp strain of fibers in a yarn and effective elastic modulus of yarns as random variables. The model is demonstrated on jute fiber yarns. Beta and normal probability distribution functions are selected to describe the statistical distributions of the crimp strain and effective elastic modulus, respectively. Parameters of the model are obtained from tensile testing results of jute yarns through inverse approach. The proposed model can provide accurate prediction bounds for tensile tests of jute yarns. Moreover, the proposed model is extended to predict the tensile response with progressive failure process of unidirectional fabric.

Shear performance of fibers-reinforced lightweight aggregate concrete produced with industrial waste ceramsite-Lytag after freeze-thaw action

Freeze-thaw (F-T) is an environmental hazard to concrete, severely reducing the mechanical properties and durability of concrete structures. The quantitative calculation of the shear performance of lightweight aggregate concrete (LWAC) after F-T action remains obscure. This study performed comprehensive research on basalt (BF)- and polyacrylonitrile fiber (PANF)-reinforced LWACs after F-T action, which can provide the basis for durability design. Compared with plain LWAC, specimens with fiber reinforcement showed a lower reduction in the relative dynamic elastic modulus (RDEM) and shear strength, and the shear strength and length-diameter rate of the fibers were the main impact factors. From the tests, 1.0% BF and 1.5% PANF are suggested as optimal for F-T resistance enhancement. Corresponding models are proposed to predict the changing tendencies of the shear strength, peak shear strain and shear modulus of LWACs after F-T cycles, considering the impact fibers and the environmental parameters. A statistically stochastic model was applied to predict the shear stress-strain curves after F-T action, and the calculation results match the test results well. The evaluation criteria in the standard are unsafe for LWAC F-T durability design. The F-T service life evaluation based on strength degradation could be advantageous in terms of the sustainable development of LWACs in an F-T environment.

Evaluating tissue-engineered repair material for pelvic floor dysfunction: a comparison of in vivo response to meshes implanted in rats.

Achieving better anatomic restoration and decreasing the associated complications are necessary for material repair of pelvic floor dysfunction (PFD). This studywas aimed to investigate host response to tissue-engineered repair material (TERM) in rat models by comparing different materials and study the changes in biomechanical properties over time. TERM was constructed by seeding adipose-derived stem cells (ADSCs) on electrospun poly(L-lactide)-trimethylene carbonate-glycolide (PLTG) terpolymers. The TERM, PLTG, porcine small intestine submucosa mesh (SIS), and polypropylene (PP) (n = 6/group per time point) were implanted in rats for 7, 30, 60, and 90days. Hematoxylin-eosin and Masson's trichrome staining were used to assess the host response, and mechanical testing was used to evaluate the changes in biomechanical properties. In vivo imaging showed that the ADSCs were confined to the abdominal wall and did not migrate to other organs or tissues. The TERM was encapsulated by a thicker layer of connective tissue and was associated with less reduced inflammatory scores compared with PLTG and PP over time. The vascularization of the TERM was greater than that with PP and PLTG over time (p < 0.05) and was greater than that with SIS on day 90. The ultimate tensile strain and Young's modulus of the PP group showed the greatest increases, and the TERM group followed on day 90. This TERM achieved better host integration in rat models and better biomechanical properties, and it may be an alternative material for PFD.

Experimental investigation of full-culm bamboo tubes strengthened by filled concrete and bamboo sheets under axial compression

To solve the problem of low compressive bearing capacity for the full-culm bamboos caused by their radial gradient variation and limited wall thickness, a new method, in which the concrete was filled inside the cavities of bamboo tubes and the bamboo sheets were wound onto the bamboo tubes with epoxy resin adhesive, was proposed in this paper to improve the behavior of full-culm bamboo structural members. The failure modes, ultimate bearing capacity of full-culm bamboo tubes with or without nodes, concrete-filled full-culm bamboo columns (CBs) and bamboo sheet-strengthened concrete-filled full-culm bamboo tubes (BSCBs) were investigated. Finally, the ultimate bearing capacity prediction method for CBs and BSCBs was studied based on the existing typical FRP-confined concrete columns. The results showed that the existence of bamboo nodes in the full-culm bamboo tubes may result in a decrease in the bearing capacity. In particular, the ultimate stress of specimens with relatively larger diameters and without nodes can be increased by a maximum of 18.2% compared to tubes with bamboo nodes. The ultimate bearing capacity of the full-culm bamboo tubes can obviously be increased using the scheme of filling concrete internally and strengthening by bamboo sheets externally. The average ultimate bearing capacity of CBs can be increased by a maximum of 65.3% compared with the corresponding full-culm bamboo tubes, and the average ultimate bearing capacity of BSCBs is at most 2.51 times higher than that of corresponding CBs. Although the bamboo tube and concrete cannot simultaneously reach the ultimate bearing capacity due to a certain difference in terms of their mechanical properties, such as the peak strain and elastic modulus, the ultimate bearing capacity of CBs and BSCBs can be predicted accurately using some existing typical strengthening models in terms of FRP-confined concrete columns.

Effect of water saturation on mechanical characteristics and damage behavior of cemented paste backfill

In this study, a series of experiments was conducted to examine the mechanical and damage properties of cemented paste backfill (CPB) with different water saturations (ws = 0%, 22.1%, 47.0%, 65.3%, 82.8%, and 100%). The results reveal that the UCS, peak strain, and elastic modulus first increased and then decreased, and the porosity and fractal dimension of cracks first decrease and then increase with the increase of ws. In addition, the UCS, peak strain, and elastic modulus is maximum, and the porosity and fractal dimension are minimum when the ws is 65.3%. The UCS increases with the increase of peak strain and elastic modulus, and decreases with the increase of porosity and fractal dimension, and the UCS present good quadratic polynomial functions relationship with the porosity and fractal dimension. The SEM images show that with the increase of ws from 0% to 65.3%, the hydration products increases and the pore structure decreases. When the ws exceeds 65.3%, and the pore structure begins to increase. The failure mode of the CPB is mainly tensile failure. A new damage constitutive model of CPB with different ws was constructed. The total damage D of the CPB is composed of initial damage Dp and load damage DL. The total damage evolution curve shows an S-shaped distribution, and the total damage rate evolution curve shows a normal distribution. With the increase of ws, the damage rate and the peak value of damage rate of CPB first increases and then decreases.

Post-crosslinkable thermoplastic polyurethane for control of mechanical properties after processes

Thermoplastic polyurethane (TPU) has attracted significant attention in various fields owing to its elasticity, abrasion resistance, and processability. However, high-molecular-weight TPUs need to be synthesized to achieve the desired mechanical properties, which generally require the tedious optimization of the synthetic process. Herein, we report a post-crosslinking process by which different types of TPUs with different levels of mechanical properties can be obtained. TPUs containing azide functional groups on the side chain (ATPU) are synthesized with different ratio of azide repeating units to non-azide repeating units, and post-crosslinking is performed via a click reaction using different types (soft and hard) and amounts of crosslinkers (di-alkyne) to adjust the mechanical properties of low-molecular-weight ATPU. The introduction of a soft and hard crosslinker respectively increases the strain and initial modulus. The post-crosslinking method will allow the production of TPUs with different levels of mechanical properties (strain or modulus) using a single synthetic process.

Biomechanical properties of erythrocytes circulating in artificial hearts measured by dielectrophoretic method

Blood damage is recognized as one of the major problems caused by non-physiological shear force induced by artificial hearts. At present, the generally accepted manifestation of mechanical blood damage is the amount of free hemoglobin released into the blood. However, there is little research on the changes of blood cell state after circulating in artificial hearts at the single-cell level. It is well known that the mechanical properties of cells are of enormous relevance in the regulation of cellular physiological and pathological processes. In this regard, it is highly needed to study the mechanical properties of blood cells affected by non-physiological shear force. In this paper, a dielectrophoresis-based method of measuring the mechanical properties of erythrocytes circulating in artificial hearts was proposed, which was quantified with some crucial parameters such as strain, elongation index (EI), and Young's modulus. Experimental results indicated that with the increase of the working time of artificial hearts, the deformability of erythrocytes decreased, the stiffness substantially increased, and the mechanical stability decreased, particularly at long exposure times. The proposed method provides a deep insight into the mechanism of subhemolytic damage at the single-cell level and has a great potential to serve as a new tool for in vitro evaluation of potential blood damage in artificial hearts.

Effects of hormone replacement therapy on endothelial function, arterial stiffness and myocardial deformation in women with Turner syndrome

Abstract Background/Introduction Turner syndrome (TS) is associated with increased cardiovascular risk. Purpose We investigated whether hormone replacement therapy (HRT) affects endothelial function, arterial stiffness and myocardial deformation in women with TS. Methods Twenty-five women with TS were studied in the estrogen phase of the HRT and two months after discontinuation of HRT. The following measurements were made: flow-mediated dilatation (FMD) of the brachial artery, pulse wave velocity (PWV-Complior) and central systolic blood pressure (cSBP), carotid intima-media thickness (cIMT), aortic (Ao) elastic indexes-namely Ao strain, distensibility, stiffness index and pressure strain modulus (Ep)-and left ventricular (LV) global longitudinal strain (GLS) using speckle tracking echocardiography. Ten healthy female of similar age and BMI served as control group. Results Compared to controls, women with TS on HRT had higher PWV (9.1±2.4 vs. 7.5±0.5m/s), cSBP (130±15 vs. 121±6mmHg), cIMT (0.66±0.06 vs. 0.55±0.05mm), aortic stiffness index, Ep and LA strain, and lower FMD (7.2±4 vs. 10.5±2.3%), Ao strain, Ao distensibility and GLS (−18.8±2.7 vs. −21.9±1.5%) (P&amp;lt;0.05 for all comparisons). Two months after discontinuation of HRT, all women increased FMD (11.7±6 vs. 7.2±4%) and reduced PWV (7.8±1.7 vs. 9.1±2.4m/s) and cSBP (123±14 vs. 130±15mmHg). There were no statistically significant changes in BMI, cIMT and GLS (P&amp;gt;0.05 for all comparisons). The percent decrease of cSBP was associated with the percent decrease of PWV (r=0.54) and reversely related with the percent increase of FMD (r=−0.57) (P&amp;lt;0.05 for all comparisons). Conclusion HRT in women with TS may deteriorate endothelial function contributing to increased arterial stiffness and central arterial blood pressure. Funding Acknowledgement Type of funding sources: None.

Uniaxial compression performance and stress–strain constitutive model of the aluminate cement-based UHPC after high temperature

In this study, a total of 72 prism specimens were manufactured to investigate the steel fiber volume fraction and exposure temperature on the uniaxial compression performance of the aluminate cement-based ultra-high performance concrete (A-UHPC). The main uniaxial compression performances of the A-UHPC after high temperature were examined, including the apparent characteristic, mass loss, failure mode, compressive strength, peak strain, initial elastic modulus and compressive stress–strain curve. As the exposure temperature increased, the failure mode of the non-fiber specimen showed a trend of transition from brittleness to ductility, the uniaxial compressive strength first increased and then decreased and the peak strain gradually increased. However, the initial elastic modulus continued to decrease. Subsequently, the calculation formulas of the uniaxial compressive strength, peak strain and elastic modulus considering the influence of temperature were proposed through regression analysis, and the uniaxial compression stress–strain constitutive model of the A-UHPC with 3% volume steel fiber was established and verified. Finally, the deterioration mechanism of the A-UHPC after high temperature was revealed by SEM for microscopic phase tests.

Effects of freezing and thawing cycles on over-consolidated reconstituted structural loess

The effect of freezing and thawing cycles on the behaviors of over-consolidated reconstituted structural loess was studied by routine uniaxial compression tests and uniaxial loading-unloading cyclic tests in this paper. Energy dissipation was used as a new way to investigate the structural damages during the freezing and thawing cycles. The change laws of strength, failure strain, modulus and the energy dissipation after different freezing and thawing cycles were investigated. It was found that under the experimental conditions used, freezing and thawing cycles lead a slight expansion in volume, and an obvious desiccation of the specimens. The failure strain and initial tangent modulus decreased gradually with freezing and thawing cycles, while the average resilient modulus decreased significantly after the first cycle, and then appeared impervious to a further increase of cycles. And based on that fact, the threshold value of Su1.0% for the over-consolidated reconstituted structural loess was suggested as about 225 kPa or a little higher. The UC strength decreased most intensely after first 3 cycles and then recovered a little during the 5∼10th cycles, which indicated a slight re-structuring effect during the cycles. The change trend of strength with freezing and thawing cycles was similar to that of the average energy dissipation, which further verified the structural damages induced by freezing and thawing cycles. The evolution laws of energy dissipation with axial strain could be described by parabolic curves, and the vertex of the fitting parabola usually appeared around the failure strain under various freezing and thawing cycles.

The effect of contact grouting on support load

Introduction. The paper analyzes contemporary methods of frame support design in permanent workings and reveals that contact grouting has received little attention. Contact grouting makes the tight contact between the hardened cement grout and the surrounding rock possible, whereas it is impossible when applying concrete lagging. The paper employs analytical method of arch support, grouting layer, and the surrounding rock calculation considering their softening. Analytical formulae determining support load has been obtained. The formulae take into account strain and strength characteristics of the surrounding rock, hardened cement grout, and support. Support load was calculated under various values of the grouting layer thickness and linear strain modulus and the depth of mining. The dependencies between the support load and the indicated parameters have been obtained, which makes it possible to select the cement grout composition for various mining and geological conditions. Research objective is to determine the effect produced by grouting layer thickness and strain characteristics on arch support load value in order to check its strength in various mining and geological conditions. Methods of research are built upon the physically based analytical methods of geomechanics to solve the problem of interaction between the support, grouting layer, and surrounding rock mass. Results. The results of arched support load calculation are presented for various values of grouting layer thickness, its strain characteristics, and depth of mining. Conclusions. The presence of the grouting layer in the void behind the support has a significant effect on the methods of arch support design. The developed methods take account of the fact that a layer of soft rock develops in the rock mass between the grouting layer and undisturbed rock. When the rock is being broken, its volume in this layer increases, which, in its turn, results in support load transfer growth through the grouting layer. It has been determined that the increase in the hardened cement grout strain and grouting layer thickness reduces support load.

Mechanical Performance of Vegetation-Growing Concrete Reinforced by Palm Fibers under Triaxial Compression

Fibers have been widely applied to improve the mechanical properties of natural soil and traditional cemented soils, but rarely investigated in substrates for slope eco-protection. Vegetation-growing concrete (VC) substrate is a kind of ecological cemented soil and has very wide popularization and application prospects. In this study, unconsolidated-undrained (UU) triaxial compression tests were conducted on the control specimens of VC substrate containing three cement contents and the palm fiber reinforced specimens manufactured by adding four fiber contents. The control specimens were shown to possess increasing yield strength, ultimate strength, yield strain and shear modulus with cement content, which resulted from the cemented texture improved by the hydrate products as recognized previously. Instead of inextensible reinforcement provided by cement, the palm fibers were found to provide extensible reinforcement, through which the obvious softening behavior of VC substrate could transfer to elasto-plasticity. Attributed to the unique ductility, the fibers added could bring with considerable increase in ductility of reinforced substrate, except for additional increases in yield strength, ultimate strength and yield strain.

Research progress on the dynamic compressive properties of ultra-high performance concrete under high strain rates

Ultra-high performance concrete (UHPC) has been accepted rapidly attributed to its superior mechanical performance and the split Hopkinson pressure bar (SHPB) is being widely utilized to evaluate the dynamic compressive properties of UHPC. Numerous studies have been performed on the dynamic behaviour of UHPC, however, a systematic summary and analysis on the dynamic compressive properties of UHPC tested by SHPB is still missing. The review starts by introducing the advantages, deficiencies and improvement methods of SHPB system. Dynamic compressive properties including dynamic compressive strength, peak strain, stress-strain relationship and dynamic elastic modulus are analyzed. The effects of steel fiber (content, type, orientations and hybrid), temperature condition, coarse aggregate, nanomaterials, size effect and loading rate on the dynamic characteristics of UHPC are comprehensively discussed. Dynamic increase factor, energy absorption characteristics and their models are summarized. Then, the dynamic constitutive model and the dynamic failure pattern are evaluated. Based on the analysis, prediction models of dynamic strength and energy absorption are proposed by considering the strain rate and volume of steel fiber, further, a new failure mechanism of UHPC under different strain rates is proposed. Finally, the topics requiring further study are highlighted. It is expected that this paper can provide references for prospective research on dynamic characteristics of UHPC.

Dynamic Triaxial Test and Microscopic Study of Solidified Muddy Soil With Different Mixing Ratios and Curing Ages

Aiming to explore the optimal mixture ratio and curing age of solidified muddy soil under dynamic load, the paper intends to investigate whether the solidified muddy soil can be used as filling of high-speed railway subgrade. Based on the dynamic triaxial test, the investigation measured the dynamic strain and dynamic elastic modulus of solidified muddy soil under different mix ratios and curing ages, and also observed the microscopic morphology of solidified muddy soil samples by using scanning electron microscope. The results show that the addition of cement and curing agent significantly increases the dynamic strength and elastic modulus of muddy soil, which effectively improve the dynamic characteristics of muddy soil. The curing effect of the curing agent is more obvious with the increase of the dosage of cement and curing agent under different mix ratio. The content of curing agent plays a leading role in the hydration reaction between cement, curing agent and soil particles. Additionally, in case of the same test conditions, when the ratio of cement mass to dry silt mass is 1:20, the ratio of diluent volume to dry silt mass is 1:20, with 28 days of curing age, its curing effect will reach the best.

Te2Br: A new one-dimensional semiconductor with direct-band gap, high carrier mobility, superior flexibility, and strong quantum confinement effect

Exfoliation of two-dimensional materials into mono- or few-layer sheets has attracted humongous interest in exploring low-dimensional materials. Here we extend this idea to one-dimensional van der Waals material Te2Br. Bulk Te2Br is formed by periodically stacking single-chain atomic crystal. Using first-principles calculations, Te2Br has lower cleavage energy than tellurium, indicating that the single- or few-chain systems could be prepared from the bulk phase. The single-chain exhibits remarkable flexibility with strain modulus of only 9.80 eV Å−1 and can resist to 25% tensile strain along the chain direction before rupture. The decrease in the number of chains results in not only a band gap increase but also an indirect-to-direct band gap transition, indicating a strong quantum confinement effect. These nanochains possess moderate band gaps, which have potential applications in optoelectronic devices with photoresponse in the UV-visible spectral range. All of these findings make Te2Br a promising candidate for future nanoelectronic devices.

An unsupervised learning approach to ultrasound strain elastography with spatio-temporal consistency

Quasi-static ultrasound elastography (USE) is an imaging modality that measures deformation (i.e. strain) of tissue in response to an applied mechanical force. In USE, the strain modulus is traditionally obtained by deriving the displacement field estimated between a pair of radio-frequency data. In this work we propose a recurrent network architecture with convolutional long-short-term memory decoder blocks to improve displacement estimation and spatio-temporal continuity between time series ultrasound frames. The network is trained in an unsupervised way, by optimising a similarity metric between the reference and compressed image. Our training loss is also composed of a regularisation term that preserves displacement continuity by directly optimising the strain smoothness, and a temporal continuity term that enforces consistency between successive strain predictions. In addition, we propose an open-access in vivo database for quasi-static USE, which consists of radio-frequency data sequences captured on the arm of a human volunteer. Our results from numerical simulation and in vivo data suggest that our recurrent neural network can account for larger deformations, as compared with two other feed-forward neural networks. In all experiments, our recurrent network outperformed the state-of-the-art for both learning-based and optimisation-based methods, in terms of elastographic signal-to-noise ratio, strain consistency, and image similarity. Finally, our open-source code provides a 3D-slicer visualisation module that can be used to process ultrasound RF frames in real-time, at a rate of up to 20 frames per second, using a standard GPU.

Effects of extruder temperatures and raster orientations on mechanical properties of the FFF-processed polylactic-acid (PLA) material

Purpose The purpose of this study is to investigate the influences of extruder temperatures and raster orientations on the mechanical properties of polylactic-acid (PLA) material processed by using fused filament fabrication (FFF). Design/methodology/approach In this research, the PLA specimens were first printed with nozzle or extruder temperatures of 205°C, 215°C and 225°C and then evaluated in terms of their physical, chemical and mechanical properties. An appropriate extruder temperature was then selected based on this experiment and used for the printing of the other PLA specimens having various raster orientations. A series of tensile tests were carried out again to investigate the influence of raster orientations on the tensile strength, tensile strain and elastic modulus of those FFF-processed PLA materials. In the end, the one-way ANOVA was applied for the statistical analysis and the Mohr’s circle was established to aid in the analysis of the data obtained in this experiment. Findings The result of this study shows that the chemistry, porosity, degree of crystallinity and mechanical properties (tensile strength, strain and elastic modulus) of the PLA material printed with a raster angle of 0° were all insensitive to the increasing extruder temperature from 205°C to 225°C. Meanwhile, the mechanical properties of such printed PLA material were obviously influenced by its raster orientation. In this case, a PLA material with a raster orientation parallel to its loading axis, i.e. those with a raster angle of θ = 0°, was found as the strongest material. Meanwhile, the raster configuration-oriented perpendicular to its loading axis or θ = 90° yielded the weakest PLA material. The results of the tensile tests for the PLA material printed with bidirectional raster orientations, i.e. θ = 0°/90° and 45°/−45° demonstrated their strengths with values falling between those of the materials having unidirectional raster θ = 0° and 90°. Furthermore, the result of the analysis by using a well-known Mohr’s circle confirmed the experimental tensile strengths and the failure mechanisms of the PLA material that had been printed with various raster orientations. Originality/value This study presented consistent results on the chemistry, physical, degree of crystallinity and mechanical properties of the FFF-processed PLA in responding to the increasing extruder temperature from 205°C to 225°C applied during the printing process. Unlike the results of the previous studies, all these properties were also found to be insensitive to the increase of extruder temperature. Also, the result of this research demonstrates the usability of Mohr’s circle in the analysis of stresses working on an FFF-processed PLA material in responding to the changes in raster orientation printed in this material.

Tensile properties of the FFF-processed thermoplastic polyurethane (TPU) elastomer

Fused filament fabrication (FFF) has become one of the most popular, practical, and low-cost additive manufacturing techniques for fabricating geometrically complex thermoplastic polyurethane (TPU) elastomer. However, there are still some uncertainties concerning the relationship between several operating parameters applied in this technique and the mechanical properties of the processed material. In this research, the influences of extruder temperature and raster orientation on the mechanical properties of the FFF-processed TPU elastomer were studied. A series of uniaxial tensile tests was carried out to determine tensile strength, strain, and elastic modulus of TPU elastomer that had been printed with various extruder temperatures, i.e., 190–230 °C, and raster angles, i.e., 0–90°. Thermal and chemical characterizations were also conducted to support the analysis in this research. The results showed the ductile and elastic characteristics of the FFF-processed TPU, with specific tensile strength and strain that could reach up to 39 MPa and 600%, respectively. The failure mechanisms operating on the FFF-processed TPU and the result of stress analysis by using the developed Mohr’s circle are also discussed in this paper. In conclusion, the extrusion temperature of 200 °C and raster angle of 0° could be preferred to be applied in the FFF process to achieve high strength and ductile TPU elastomer.

Manufacturing and Characterization of Open-Cell Aluminum Foam Produced via Infiltration of Leachable Space Holder

Open-cell Al-Si foam samples were produced using infiltration casting technique. The metal infiltration process was performed in a specially designed and built setup consisting of a vertical chamber resistance furnace, a pressurization chamber connected to an Argon gas cylinder through a control manifold. To control the relative density of the produced foams, non-compacted and compacted preforms (5 MPa) were prepared from 2 or 4 mm NaCl particles. The compaction was performed using a hydraulic press in the same infiltration chamber. Argon pressure of 3 bars was applied to infiltrate the preforms with the aluminum alloy after melting at 750 °C. The produced aluminum foam specimens show no lack of filling, a high degree of preform replication, and good homogeneity of pore sizes. The preliminary physical and mechanical characterization tests, including relative density, plateau stress, densification strain, and elastic modulus of the foam, are comparable to the values reported in previous investigations, in which more complicated, time-consuming, higher energy, and costly techniques were used. Further investigations on wider ranges of particle sizes, compaction, and infiltration pressures are currently in progress.