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The growth and advancements done in solid mechanics and metallurgy have come up with various characterization techniques that help in prediction of elastic properties of different types of materials—isotropic, anisotropic, transverse isotropic, etc. Soft tissues which refer to fibrous tissues, fat, blood vessels, muscles and other tissues that support the body were found to have some control over its mechanical properties. This mechanical behavior of soft tissues has recently shifted the attention of many researchers to develop methods to characterize and describe the mechanical response of soft tissues. The paper discusses the biomechanical nature of soft tissues and the work done to characterize their elastic properties. The paper gives a review of the behavior and characteristics of soft tissues extracted from various experimental tests employed in their characterization. Soft tissues exhibit complex behavior and various complexities are involved in their experimental testing due to their small size and fragile nature. The paper focuses on the conventionally used tensile and compression tests and the difficulties encountered in soft tissue characterization. It also describes the utility of ultrasound technique which is a non-destructive method to characterize soft tissues. Tensile and compression test used to characterize materials are destructive in nature. Ultrasound technique can provide a better way to characterize material in a non-destructive manner [ABSTRACT FROM AUTHOR]

Additive Manufacturing (AM) techniques, particularly Fused Filament Fabrication (FFF), have revolutionized prototyping and low-volume production. Improving the tensile properties of FFF-printed parts is a primary objective to elevate their functional utility. This study aimed to investigate the effects of annealing time (ATM), annealing temperature (ATP), and nozzle diameter (ND) on the tensile strength (TS) of two commonly used printing materials: Polyethylene Terephthalate Glycol (PETG) and PETG reinforced with carbon fibre (PETG-CF). Samples with varying ND (0.4 mm, 0.6 mm, and 0.8 mm) underwent annealing at ATP of 80°C and 100°C for ATM of 60 min and 120 min, respectively. Subsequent tensile tests were meticulously conducted, and regression models were employed to comprehensively analyse the influence of these control factors on TS. The findings from the tensile tests on annealed specimens revealed substantial improvements in TS for both PETG and PETG-CF materials. Statistical analysis, Taguchi method (TM), and response surface methodology (RSM) indicated that ND exerted a more pronounced impact on TS compared to ATM and ATP. By identifying the optimal control factor combinations for each material, the study pinpointed that the best TS was achieved at 0.8 mm ND, 120 minutes ATM, and 100°C ATP for PETG-CF. The remarkable enhancement in tensile properties for annealed FFF-printed parts underscores the potential of PETG-CF to replace structural metallic components in critical applications within the automotive and aeronautical industries. [ABSTRACT FROM AUTHOR]

The performance of high-strength steel (HSS) welding joints is crucial for tubular structure design. This paper investigates the hysteretic performance of HSS square hollow section (SHS) T joints considering fracture behaviors. The hysteresis and tensile tests of the HSS SHS T joints and a comparative analysis of failure modes and bearing capacity are conducted. Parameter analysis is conducted based on the validated FE model considering fracture and elastoplastic constitutive relationship with a wide range of parameters covered, including the cross-sectional width ratio and the wall thickness ratio between brace and chord, and the width-thickness ratio of the chord, and the seam weld size of the joint connection. The results show that fracture behavior can affect the failure mode and bearing capacity of the joints, and it cannot be ignored in the hysteresis analysis process. The energy consumption capacity and the ductility coefficients increase when β increases from 0.2 to 1.0, τ increases from 0.3 to 1.0 and 2 γ decreases from 40 to 20. Meanwhile, joints' failure modes and residual strength vary with the above parameters. It is necessary to use the damage fracture constitutive model of steel in numerical simulation. [ABSTRACT FROM AUTHOR]

This study investigated the effectiveness of carbon fibre-reinforced polymer (CFRP) materials in strengthening the diagonal tension members of steel-truss bridges. Monotonic tensile and cyclic loading tests were performed on CFRP-strengthened specimens with variations in the CFRP-bonding range on the flanges. This study focused on the strengthening methods A and B, which were proposed to address insufficient CFRP anchoring near gusset plates by bonding CFRP sheets to both sides of the flanges of the diagonal tension members. The results of the monotonic tensile loading tests indicated a significant increase in tensile stiffness and substantial improvements in yield strength (27%) and ultimate load-bearing capacity (51%) when the strengthening methods A and B were employed. Delamination of the bonded CFRP sheets was effectively delayed, occurring only after the steel yielded, owing to the use of a ductile adhesive (polyurea putty). On the other hand, the cyclic loading tests demonstrated a significant enhancement in the load-bearing capacities (33% for tensile, 32% for compressive) of the strengthened specimens. Moreover, the energy dissipation capacities of the specimens strengthened by methods A and B exhibited linear increases, with 12% and 14% higher values respectively than those of the non-strengthened specimen. Although the stiffnesses (tensile and compressive) of the strengthened specimens decreased in each loading loop, the strengthening methods A and B maintained the stiffness values at approximately 35% higher than those of the non-strengthened specimen. [ABSTRACT FROM AUTHOR]

Ulexite and colemanite filled acrylonitrile-butadiene-styrene parts are manufactured by injection molding method. Tensile and wear tests are applied to reveal specific properties of composite parts. Various characterization methods are used to confirm the filler-matrix interactions, polymer melt flow, friction mechanisms, and fracture modes. This study investigated the use of ulexite and colemanite as fillers in acrylonitrile-butadiene-styrene composite parts, focusing on their impact on mechanical and frictional properties. Results showed that the addition of ulexite and colemanite fillers significantly improved mechanical properties such as compared to pure ABS, however ulexite filler showed much better performance compared to colemanite. In terms of wear test, ulexite filled ABS specimen showed a smooth wear while pure and colemanite filled ABS provided severe wear characteristics. These findings have implications for the development of high-performance composite materials for use in industries such as automotive and aerospace. [ABSTRACT FROM AUTHOR]

Coated fabrics can experience mechanical performance degradation due to environmental factors and long-term stress during service. Hence, studying the mechanical behaviors of these materials after aging is crucial. While PTFE (polytetrafluoroethylene)-coated fabrics are more commonly used than PVC (polyvinyl chloride)-coated fabrics, limited research exists on their performance after aging in practical engineering applications. PTFE-coated fabrics are primarily used in large-span fabric structures, where their mechanical performance under tensile-shear stress is crucial. This study aims to investigate the mechanical behaviors of PTFE-coated fabrics after practical aging under tension-shear stress. Test materials included decommissioned Saint-Gobain Sheerfill-II PTFE-coated fabrics, which had served for 23 years at Shanghai Stadium, and identical new fabrics. Monotonic tensile, central tearing, and cyclic tensile tests were conducted at seven different off-axis angles to compare the mechanical properties of aged fabrics with new fabrics, including tensile strength, tearing strength, modulus of elasticity, and ratcheting strain. Additionally, this study explored changes in failure mechanisms, tearing mechanisms, applicability of strength criteria, and suitability of the orthotropic model after aging. This provides a comprehensive understanding of the mechanical behaviors of aged PTFE-coated fabrics and valuable insights for engineering design. [ABSTRACT FROM AUTHOR]

This paper presents a numerical study of the influence of geometry and orientation of fibres on the mechanical behaviour of a hemp fibre reinforced polypropylene, obtained with injection. Tensile tests and multiplexing mode Dynamic Mechanical Analysis (DMA) were carried out in order to determine the mechanical behaviour of the neat and reinforced material. A numerical homogenization was then performed with the elastic hemp fibres for aligned and random orientation as well as a reconstructed microstructure obtained with injection simulation to correlate with tensile tests. The simulations were performed for sphero-cylinder and curved fibres and the results were compared to FFT results obtained directly on micro-tomography images as well as experimental data. The results showed that the complex geometry of the fibres can be approximated with a random 3D orientation of sphero-cylinder shaped fibres, a reasonable hypothesis leading to a simplification of the problem and an easier process of design of parts made with such materials. [ABSTRACT FROM AUTHOR]

This article examines the compressive behavior of re-entrant auxetic structures to optimize its energy absorption. The unique properties of auxetic structures have made them popular in various industries, especially for sports equipment. This study aims to create different types of structures using an FDM 3D printer. First, an appropriate raster angle for 3D printing of tensile test samples is examined for PLA and PLA+ materials. Next, three types of structures are constructed using brittle PLA and ductile PLA+ materials, and their energy absorption is compared. These structures are homogeneous auxetic re-entrant (HAR), unilateral graded thickness (UGT), and bilateral graded thickness (BGT). Changing from brittle (PLA) to soft material (PLA+) increases energy absorption in all structures. Likewise, grading the thickness of the structure, especially on BGT, increases energy absorption. Simulation results are validated by modeling the structures in two ways for brittle and ductile materials using Abaqus software. Finally, based on the simulation results, the most appropriate step of the bilateral graded thickness is recognized as 0.8-1-1.2. [ABSTRACT FROM AUTHOR]

Automotive bumper beams play a very crucial role in absorbing impact energy during crash collisions and reducing damage from the front or rear ends of the vehicle during low or high-velocity impact. This paper discusses the impact of different energy-absorbing materials introduced between the fascia and the metallic beam. A novel recipe, with combinations ranging from 0% to 50% and 20% to 80% of Polypropylene (PP) with Ethylene vinyl acetate (EVA) and Polypropylene (PP) with Ethylene propylene diene monomer (EPDM), was prepared by weight and comparative study based on their impact strengths was done both experimentally and numerically. The mechanical properties of the polymer blends have been determined under tensile, compressive, and impact testing. Results obtained from numerical simulation analysis lie in reasonable agreement with the experimental findings. The tensile and compression test results show that polymer blend PP/EPDM-50/50 is the best selection as an energy absorber due to its ductility and toughness properties which is evident from experimental testing. The introduction of this blend in front of the metallic strip (bumper beam) has significantly supported the improvement in the energy-absorbing capacity and impact strength. [ABSTRACT FROM AUTHOR]

Composite materials are increasingly used in a broad range of applications due to their recognizable mechanical properties and the high strength-to-weight ratio. The aim of the current study is to improve the mechanical properties and fracture toughness of composite laminates. Several types of fabrics, such as glass, carbon, and Kevlar, and micro-particles are adopted to create composite laminates via the vacuum infusion method. The mechanical performances of the proposed laminates were evaluated via tensile and flexural strength tests. Moreover, the impact strength tests were conducted to examine their dynamic performances. Results showed that woven laminates such as glass woven, carbon woven, and Kevlar woven composites with micro-particles revealed better tensile properties compared with those without micro-particles. For instance, enhancement in the Young's modulus with around 5%, 6%, and 13% were resulted from the glass, carbon, and Kevlar fabrics with fillers, respectively. Furthermore, higher impact strength and fracture toughness were obtained from the laminates of glass, carbon and Kevlar with inclusion of thermoplastic particles. For example, the glass, carbon and Kevlar fabrics composites with fillers samples showed improvement in the fracture toughness with around 24%, 17% and 14%, respectively. In addition, numerical simulation findings of flexural failure load and damage failure modes were in accordance with experimental results both qualitatively and quantitatively. [ABSTRACT FROM AUTHOR]

For their use in polymer and composite materials engineering, and with a view to sustainable development, a great deal of work has been carried out with the aim of describing the properties of plant fibers. This work presents the effects of the extraction method on the chemical, physical and mechanical properties of oil palm petiole fibers (OPPF). To this end, the FPPH to be analyzed were obtained by water retting and chemical retting with soda (5% solution). Their physico-chemical and mechanical characteristics were then studied and compared. Fourier transform infrared spectroscopy (FTIR) analysis confirmed the existence of the main components of lignocellulosic fiber (lignin, cellulose and hemicellulose). Lignin was reduced by 22.74%, hemicellulose by 27.33% and cellulose by 16.87% compared to water retting. XRD revealed a crystallinity index of 58.66% for fibers extracted with a 5% sodium solution and 58.51% for fibers extracted with water retting. Soda retting reduces density by 3%. Tensile tests revealed an average tensile strength of 156.082 MPa for water-rubbed fibers and 205.875 MPa for soda-rubbed fibers, Young's modulus of 3.432 GPa for water-rubbed fibers and 5.346 GPa for soda-rubbed fibers. Elongation at break for FPPH extracted by water retting was 5.178% and 4.41% respectively. This shows that the extraction method affects mechanical properties (flexibility and stiffness) and should be chosen according to the desired characteristic. [ABSTRACT FROM AUTHOR]

In order to improve structural fire-resistant behaviors, this paper designed a two-layer functionally graded ultra-high performance concrete (FGUHPC) structure composed of a UHPC layer and a lightweight aggregate concrete (LWAC) layer. UHPC layers are adopted to provide structural bearing capacity and protected by LWAC layers from elevated temperature. Splitting tensile tests and three-point flexural tests were conducted under ambient and elevated temperatures to evaluate interfacial bond performance and flexural bearing capacity, where two interfacial treatments were adopted and compared. The experimental results revealed that FGUHPC members exhibited good integrity during heating, no explosive spalling occurred and the maximal temperature at interfacial regions was 266°C. The interfaces showed desirable bond performance under ambient temperature while the splitting tensile strength was decreased by around 85% in the case of high temperature. Flexural test results indicated that the structural stiffness would be reduced by around 42% under elevated temperature, as a result, the maximal deflection was increased from 2.5 mm to 3.7 mm. SWM could significantly improve interfacial bond performance and prevent debonding failure of specimens at the postfire state, leading to higher structural bearing capacities. The bearing capacities of specimens with and without interfacial treatments were 42.7 kN and 38.4 kN respectively under ambient temperature, which remained about 88% after elevated temperature. [ABSTRACT FROM AUTHOR]

Mechanical properties of short fiber reinforced composites manufactured with fused deposition modeling is affected by variables such as printing properties and internal structure of the composite. In this study, the relation between the tensile properties of 3D-printed short fiber reinforced composites, printing orientation and internal structure is inspected. Samples of different printing orientations are manufactured. These samples are inspected under X-ray micro computed tomography (micro-CT) and their fiber orientation distributions and fiber properties are determined. Then, these internal structure properties are applied to analytical material models to estimate the tensile properties of composites. Estimated material properties are compared with tensile test results. It turns out that analytical models that consider internal structure properties provide more accurate estimations than other analytical models that does not take these into account. [ABSTRACT FROM AUTHOR]

A wound dressing is important to ensure an efficient healing process while protecting the wound area. This research study combined 2-hydroxyethyl cellulose (2HEC)—an etherified cellulose derivative with salicylic acid (SA) to develop a single layer and investigate the 2HEC viability as wound dressing material. Nine different samples with different compositions of SA, from 5 wt.% to 40 wt.% (with an interval of 5 wt.%) and one control sample without adding SA were prepared via the solution casting method. The 2HEC-SA films were studied regarding the effects of SA composition on antimicrobial properties (Staphylococcus aureus) via the well-diffusion method. Additionally, degradability, mechanical properties, X-ray diffraction (XRD), and Fourier transform infrared (FTIR) of 2HEC-SA films have also been tested. The strongest antimicrobial effect of 2HEC-SA film was obtained at 40 wt.% with a 16 mm inhibition zone diameter. There was a noticeable decreasing weight loss pattern in the degradation test and the tensile strength of 2HEC-SA film when the composition of salicylic acid is increased. 2HEC-SA film changes phases from amorphous to crystalline starting at 25 wt.% of salicylic acid as seen through XRD, while FTIR shows that complexation of 2HEC and salicylic acid occurred at 1050 cm−1. [ABSTRACT FROM AUTHOR]

High-strength steel (HSS) can effectively and economically design structural members that withstand large forces induced by extreme events such as earthquakes. To evaluate the seismic performance of HSS members and structures using nonlinear finite element (FE) analyses, using an accurate material model is important, which can simulate the inelastic cyclic behavior of the HSS. The peculiar material behavior of HSS needs to be considered in the model. This study used a combined hardening model to construct the material model. The configuration of the model and the constituent model parameter values are determined to precisely simulate the low-cycle fatigue (LCF) behavior of HSS. An efficient particle swarm optimization (PSO) algorithm is used to determine parameter values with LCF test data of 54 individual HSS coupons. In additions, to conveniently determine the model parameter values with only monotonic tensile test data instead of conducting expensive LCT tests, empirical equations are proposed. It is shown that the LCF curves of HSS can be accurately simulated using the constructed material model with the proposed equations. [ABSTRACT FROM AUTHOR]

Recently, composite PVDF membranes with good performance have triggered enormous interest because of their great potential application. However, the uncertainty of mechanical properties limits their application. Herein, this paper reveals the elastic modulus properties of the loading angle between warp and tensile direction using the uni-axial tensile test of SH-1050P membrane textile. In addition, the bi-axial tensile test with different loading ratios was implemented. Both uni-axial and bi-axial ductile load-displacement/stress-strain curves are featured. It is the first to establish a relationship between the elastic modulus and the loading angle using a theoretical method based on the assumption that there is no slippage and crease between yarns and matric. Furthermore, simulations with different textile parameters were carried out to verify the theoretical results. The key finding is that the elastic modulus under uni-axial load can be divided into two stages, which are elasticity and plasticity. Both of which are proportional to the sine function applied to two times the loading angle. The Poisson's ratio of SH-1050P textile can be considered as a fixed value of 0.11. This conclusion can be extended to similar textiles. The outcome of this paper contributes to a deeper understanding of the PVDF memrane's mechanical behavior and presents a novel insight into its response to different loading conditions. [ABSTRACT FROM AUTHOR]

Sheet molding compounds (SMCs) as an alternative material for low-cost and lightweight automotive structural components require special attention to their failure behavior and collision safety. This study aims to analyze the energy-absorbing response and variability of unsaturated polyester matrix SMCs under the range of strain rates from 10−3/s to 500/s through quasi-static and dynamic tensile tests. Additionally, the tensile process and fracture morphology were characterized using Digital Image Correlation and Scanning Electron Microscopy to reveal the underlying rate-dependent failure mechanism. The results demonstrate a pronounced positive correlation between the tensile strength and absorbed energy of SMCs with strain rates. Specially, the absorbed energy exhibits substantial variability, primarily attributable to the plastic damage behavior during the nonlinear phase. A transition in the failure mode from debonding to pseudo-delamination, accompanied by a more extensive failure area at high strain rates, serves as the main mechanism for enhancing the material energy absorption capacity. [ABSTRACT FROM AUTHOR]

Fused deposition modeling (FDM) is one of the additive manufacturing (AM) techniques in which intricate shapes are produced effectively with time and cost. Thermoplastics and filler-incorporated thermoplastics composite materials were used in the form of filament. The mechanical properties of the printed sample varies with the parameters involved in FDM printing. In the present investigation, polyamide 6 (PA) with 20 wt.% of short carbon fiber (CF) was used as filament. The filaments were printed with different raster orientations namely 0°, 45°, 90°, and ±45° by keeping other printing parameters constant such as 100% infill density, 0.2 mm layer thickness, 30 mm/min printing speed, 240°C printing temperature, 80°C bed temperature, and XY or 0° body orientation with a clear justification studied. The printed samples were investigated for structure, morphology and mechanical properties using tensile test and impact test respectively. The results shows that bidirectional ±45° raster orientation specimens show the highest tensile strength of 35.2 MPa in comparison with 0°,45°, and 90° raster orientation, and PACF composite material showed improved mechanical properties as compared to pure PA. The highest impact energy was observed for a PACF composite with a raster orientation of 90°. Morphological analysis of composites showed a uniform dispersion of CF in PA matrix and improved interfacial adhesion between matrix and reinforcement. [ABSTRACT FROM AUTHOR]

This study investigates the performance degradation and prediction of polyvinylidene fluoride (PVDF) membrane materials under natural aging conditions (2 MPa prestress) and artificially accelerated aging conditions. Initially, the tensile strength, elongation at break, elastic modulus, tear strength, and apparent properties (transmittance, reflectivity, and conjugated double bond absorption area) of the membrane material were measured through uniaxial tensile testing, trapezoidal tear testing, and ultraviolet (UV) testing. These measurement results were then compared and analyzed in relation to tear strength and apparent properties under artificially accelerated aging conditions. The results indicate that UV irradiation and 2 MPa prestress play a crucial role in the degradation of PVDF membrane material properties. Finally, an enhanced Arrhenius equation, accounting for the triple effects of irradiation, oxygen pressure, and temperature, and Schwarzschild's law, were employed to establish a correlation between natural (2 MPa prestress) and artificially accelerated aging performance of PVDF. The results demonstrate that the enhanced Arrhenius equation provides a more accurate prediction compared to Schwarzschild's law. [ABSTRACT FROM AUTHOR]

Following the emergence of new morphology geogrids, tensile tests on some of the new morphology geogrids were conducted in this paper for practical engineering options. The study focuses on the tensile testing of 3D printed geogrids to analyze the effects of morphology differences (material, planar structure, filling rate, rib width and rib height) on the tensile properties of geogrids. The test results show that the tensile properties of high density polyethylene geogrids are stronger than those of polylactic acid geogrids. Increasing the filling rate of geogrid can increase the tensile performance while decreasing the rate of tensile performance improvement. In contrast to the elongation at the break of the geogrid, the maximum tensile strength and the maximum tensile modulus increase in the order of bidirectional, triaxial and quadaxial geogrids. When the rib width and the rib height increase by the same amount, the rib height increases the maximum tensile strength of the geogrid more than that of the rib width. [ABSTRACT FROM AUTHOR]

Introduction: Natural dyes have become very important for decades based on their extensive properties compared to synthetic dyes. Pima cotton was dyed with natural dyes derived from plants using mordants, a crucial step in modern industry. Objective: This study explores the efficacy of banana leaf-extracted natural dyes with mordants in dyeing Pima cotton, examining color properties, chemical attributes, and fastness while exploring the potential for industrial applications. Methods: In this study, banana leaf extracts were utilized for dyeing Pima cotton with mordants. The investigation assessed the multifunctional properties of alkaline and acetone using UV-Vis and FTIR or analyzed the dyed fabric's UPF. Applied to pre-mordanted Pima cotton, our dye interacts with various mordants like ferrous sulfate (Fe2SO4), copper sulfate (CuSO4), and potassium dichromate (K2Cr2O7). Factors influencing dye fixation on Pima cotton, including cellulose and mordants, were examined. Treated and untreated fabric samples were tested for tensile strength and elongation. Dyeing performance was assessed using color parameters (K/S, L*, a*, b*, ΔE) using the Kubelka-Munk equation and fastness properties, with consistent results compared to standard protocols. Results: The study on natural dye extraction from banana leaves has yielded promising outcomes, showcasing the effectiveness of mordants in dye fixation on cotton. The results demonstrate high tensile strength, color strength, and fastness properties in the dyed Pima cotton samples. Statistical analysis highlighted the nuanced relationship between mordants and dyes. The study's comprehensive approach, UV-Vis and FTIR analyses, dyeing temperature optimization, and phytochemical screening, confirming the presence of flavonoids, saponins, alkaloids, and other bioactive compounds, positions banana leaf extracts as a sustainable and versatile resource for eco-friendly textile practices, offering a compelling alternative to synthetic dyes. Conclusion: The study reveals Pima cotton's promising potential for eco-friendly dyeing, optimizing cost, time, and space for future sustainable textile applications. [ABSTRACT FROM AUTHOR]

This paper is concerned with the determination of the yield surface in a two-dimensional stress field within an undergraduate Mechanics of Materials student laboratory experiment. In this experiment, the two-dimensional stress field is obtained by subjecting a steel specimen to a combined bending and torsion load. The motivation for the paper was the lack of correlation between the von Mises and Tresca yield criteria and the principal stresses calculated at the load at which students were predicting material yielding. The latter yield loci were based on the uniaxial 0.2% proof stress. The lack of correlation was creating a lot of frustration amongst students. This is undesirable, especially within an undergraduate student experiment. Two hypotheses for the lack of agreement were considered. The first hypothesis was the uncertainty involved in the method that the students were using to predict the onset of material yielding. The second hypothesis was that the specimens being used for the experiment had anisotropic properties, given that little information on their manufacture was provided. The need for determining accurate yield stress values and on methodologies found in literature that are used to determine the material proof stress or lower yield stress in a uniaxial tensile test are discussed. Four methods taken from literature are used and adapted to detect the first yield of the specimen under a combined bending and torsional load. The resulting experimentally yield loci are compared with the theoretical von Mises and Tresca isotropic yield loci over half of the second quadrant of the two-dimensional principal stress field plot. Correlation between the four methods was quite good but not so when compared with the von Mises and Tresca' loci. A lack of correlation occurred for an increasing torsional load indicating a possible anisotropy in the material properties. These results hinted towards the second hypothesis. A number of tensile test specimens were hence heat treated so as to induce isotropy in the material properties. The combined loading experiments were repeated using the heat-treated samples. A very good correlation was obtained between the experimental yield points for the two-dimensional stress field and the von Mises and Tresca yield loci. This good correlation for the heat-treated specimens confirmed the authors' second hypothesis on the anisotropic properties in the as-received state and, therefore, the requirement to heat treat the specimens for a meaningful student undergraduate laboratory activity. [ABSTRACT FROM AUTHOR]

Lattice materials are one of the most desirable and widely used materials due to the characteristics derived from their geometrical formation as opposed to their chemical composition. In this article, a lattice material has been designed and printed using polymer filament wire made of polylactic acid (PLA) and fused deposition modelling (FDM), followed by mechanical testing. In addition, tensile testing of the PLA printed samples has also been carried out to ascertain the tensile properties of the material in use, and the material has shown 38–40 MPa tensile strength with a Young's modulus value of 1538 ± 120 MPa. The lattice was designed using 3D CAD software, and numerical results were obtained using the Autodesk Inventor simulation module. In addition to the experimental test, theoretical tests were also conducted, and the results were compared to the experimental results. With this methodology, the lattice material failure process can be comprehended. Along with the lattices, the PLA tensile test samples were also prepared and tested to check the feasibility of the PLA being used and ascertain the properties. In addition, it has been observed that after a specific load and deformation, the material's resistance increases due to its increased density and repeated cell interference. The major purpose of the study is to explore the aspects and feasibility of the PLA printed lattice material with complex shapes and explore the application potential of such shapes. [ABSTRACT FROM AUTHOR]

Starch and cellulose being both carbohydrate polymers, thermoplastic starch (TPS) is expected to be a suitable compatibilizer for materials made of cellulosic fillers and polyesters. This paper investigates the interactions between TPS and cellulose in Poly(butylene adipate-co-terephthalate) (PBAT), melt-blended composites. For this, microfibrillated cellulose (MFC) were dispersed in a commercially available polymer (Mater-Bi, MB), containing TPS already dispersed in PBAT. Microscopic observations were performed on composites based on either MB or neat PBAT reinforced with microfibrillated cellulose (MFC). Tensile tests and dynamic mechanical analysis in solid and in the molten state revealed a percolating network of fillers. Results indicated interaction between TPS and cellulose as the origin of the adhesion of the components but also of biphasic agglomerates. Graphical Abstract [ABSTRACT FROM AUTHOR]

Discontinuous-long-fibre (DLF) composites fabricated from pre-impregnated unidirectional (UD) fibre chips are susceptible to structural deficiency. The in-plane highly anisotropic mechanical properties of the chips combined with the random nature of fibre orientation causes local weaknesses within the material when fibres are perpendicular to the load. Recent experimental results have shown that using woven-fibre chips could improve the performance of DLF composites by increasing their average mechanical properties and reducing their variability. To better understand the underlying phenomenon giving an advantage to the woven chips, a finite element model was developed to predict the mechanical properties obtained from a standard tensile test. DLF chips were modelled based on a voxel method where random chip positions were generated by an algorithm developed in this work. ANSYS® software was utilized to model the non-linear response associated with progressive damage of the composite. The maximum stress and the Puck failure criteria were employed to define damage initiation for the woven and UD fibres, respectively. Tensile modulus predictions for both types of chips showed good results when compared to experimental data. Strength predictions for the UD fibres also showed good correlation with experimental results, but the model overestimated the strength of the woven-fibre DLF composite. It appeared that the failure of the UD-fibre composites was associated with matrix failure (transverse tension and in-plane shear). Woven-fibre composites, however, showed damage modes linked to both fibre failure (longitudinal tension) and matrix failure (transverse tension and in-plane shear). [ABSTRACT FROM AUTHOR]

For the totally incompressible Yeoh (i.e., classic Yeoh) model predicts the equibiaxial tension (ET) stress lower, this paper proposes the totally incompressible Yeoh-Revised model to improve the prediction of ET stress. First, the fitting expression of the totally incompressible Yeoh-Revised constitutive model was derived under the presumption that fluororubber (FPM) and hydrogenated nitrile-butadiene rubber (HNBR) are isotropic and entirely incompressible. Meanwhile, the goodness-of-fit (R^2) statistic was used to assess the fitting outcomes of the three tension tests data (e.g., single tension (ST), ET and planar tension (PT)). Additionally, in order to fit the rubber materials tensile test data more accurately, we suggest a novel hyperelastic constitutive fitting method that takes into account the volume microscopic compressibility of rubber materials. The findings demonstrate that the totally incompressible Yeoh-Revised model's prediction of ET stress has marginally improved which neglecting the rubber materials' volume microcompressibility, while the almost incompressible Yeoh-Revised model fits the ET stress significantly and accurately, and also enhances the forecast accuracy of overall R^2. Finally, the fitting formula of the almost incompressible constitutive model may be reduced to that of the totally incompressible model if the volume microcompressibility is disregarded, which is beneficial to more accurately forecast the experiment tests of rubber materials tension. [ABSTRACT FROM AUTHOR]

This article aims to accomplish research's that has been achieved recently in the scientific community on the manufacturing monitoring and structural health monitoring (SHM) of composite materials using in-situ piezoelectric sensors. A series of specimens of flax/Elium composite laminates with and without integrated piezoelectric sensors were subject to static and fatigue tensile tests. The effects of introducing the sensor into the composite materials were studied. Moreover, the Acoustic Emission (AE) method was used during experimental tests to follow the gradual degradation and damage evolution in the bio-composites. The AE data were analyzed by the k-means unsupervised pattern recognition algorithm. Moreover, the characteristics of the acoustic signals detected from specimens with and without integrated sensors were compared. The experimental results show that the integration of piezoelectric sensors within the flax/Elium composite without degrading its mechanical properties is possible. In addition, the integrated sensor shows good results regarding class detection and separation. The in-situ health monitoring methods performed on bio-composites presents an excellent alternative to the conventional technique in which sensors are generally bonded to the material surface. [ABSTRACT FROM AUTHOR]

An account is presented of successfully implemented Extended Producer Responsibility (EPR) with recycling to high value products, to help overcome barriers and generate confidence in moving towards Circular Economy (CE) business models. A template for organisations proposing to recycle a thermoplastic is provided by describing appropriate tests and considerations in implementing the recovery and re-use of high impact polystyrene (HIPS) based on a practical, industry case. Simulating the repeated 100% closed loop reprocessing of production scrap, original HIPS has been injection molded to produce tensile and impact test pieces, reground and reprocessed eight times. Assessing the present results together with literature, repeated recycling of production scrap is possible without the need for a remedial compounding step, or changes to processing parameters. Integral to the EPR model is recovery of plastic from returned end-of-life (EoL) products, and in relation to the in-use environment, studies of the effects of UV exposure on virgin material show that significant property degradation can occur. However, with indoor use, as in the present case, this is not seen. Within the CE business model it is desirable to use blends of recovered HIPS originating from different original resin manufacturers. Feeding dry blend regrind directly to the molding machine proved satisfactory, avoiding the need for a compounding/pelletizing step. As an outcome of this study, products are being successfully manufactured from 100% HIPS recovered from EoL products in an environmentally and economically positive CE plan. [ABSTRACT FROM AUTHOR]

Although petroleum-based polymers require a long process to decompose in nature, they still have a wide range of uses. However, due to many important reasons such as the environmental pollution problem caused by these polymers, there is an increasing interest in biodegradable polymers. Poly(lactic acid) (PLA) is a biopolymer with comparable performance to conventional polymers. However, due to its poor tribological, mechanical and thermal properties, the usage area of PLA cannot expand and its use is limited to short-term material applications. In this study, it was aimed to contribute to the expansion of the usage area of PLA by improving its poor properties. For this purpose, efficiency of graphene nanoplatelet (GnP) and/or Joncryl® addition to carbon fiber (CF) reinforced PLA matrix composites to improve the composite performance by means of improved interface interaction fiber and matrix was investigated. Within this scope, effects the separately and/or simultaneously addition of CF, GnP and Joncryl® to PLA on properties were investigated by tensile test, adhesive wear test, DSC, TGA and SEM analyses. All results revealed that the composite composition prepared by simultaneously addition of 10, 0.5 and 2 wt.% CF, GnP and Joncryl®, respectively, to pure PLA performed the best in all tests and analyses. [ABSTRACT FROM AUTHOR]

Weld-Line in an injection molded part develops when two or more melt fronts are converged together. The weld-line is unavoidable when the design is complex where two melt flow fronts are mating each other head-to-head, this mating area is mechanically weak compared to other portions of the modeled part. The decrease in strength in the weld-line area can be attributed to several factors like molecular diffusion, fiber orientation effect, unoptimized process conditions, surface tension effect, internal residual stresses, etc. The strength of the weld-line area can be increased by optimizing injection molding process parameters like melt temperature, injection speed, packing pressure, changing gate type and location, etc. The present work focuses on studying the effect of packing pressure on strength of stagnation weld-line. This has been examined with experimental testing and scanning electron micrographs of the fractured surface on the weld-line and without weld-line specimens. The special injection mold is designed and fabricated to produce plaques having stagnation weld-line. The plaques are prepared out of 30% glass-filled Polyamide 6 material. The four sets of plaques are produced by changing the magnitude of packing pressure equal to 60% of filling pressure, with increment of 20% up to 120% of filling pressure. The tensile test specimens are machined on these plaques for two different angular orientations and testing is conducted as per ISO 527-2. The results demonstrated that, without weld-line specimens, the tensile modulus, stress at break marginally increases with an increase in packing pressure, and strain at break decreases with an increase in packing pressure. However, for specimens with stagnation weld-lines, both the tensile modulus and stress at break are observed to be 42% of without weld-lines samples for minimum packing pressure. The results obtained are evident from stress-strain graphs and scanning electron micrographs. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) radiation present in natural sunlight degrades the chemical and mechanical properties of polymeric matrices in composites. Polyurea possess a unique set of chemical and mechanical properties due to its complex microstructure comprising of hard and soft segments (phases). The primary objective of the work presented here is to characterize the chemical and mechanical degradation of pure polyurea and polyurea - polyhedral oligomeric silsesquioxane (POSS) nanocomposites subjected to UV radiation exposure for 45 days. Control specimen in as-received condition (reference specimen) and UV-aged tensile test specimen are tested in the study. Analysis of Fourier transformed infrared (FTIR) spectra for UV-aged polyurea and polyurea-POSS composites reveals that the addition of POSS nanoparticles accelerate the deterioration of polyurea matrix by breaking the hard phase network and altering the mechanism of degradation for the soft phase present in polyurea microstructure. The deterioration of hard and soft segments cause a significant reduction in tensile properties of polyurea-POSS composites. [ABSTRACT FROM AUTHOR]

Plastic materials are widely used as geosynthetics. The use of plastic products poses a serious environmental risk due to their degradation. Aiming at the environmental problems caused by the difficulty of direct degradation of traditional plastic geogrid and the effects of material filling ratios, material filling forms, mesh shapes and tensile rates on the mechanical properties of geogrids. Based on 3D printing technology, polylactic acid (PLA) geogrid was prepared, and indoor tensile tests of polylactic acid geogrid were carried out. The effects of material filling ratios, material filling forms, geogrid geometries and tensile rates on the mechanical properties of geogrid are analyzed. The test results showed that PLA can be used as an environmentally friendly material for making geogrids and can reflect the mechanical properties of different geogrids. The triaxial geogrid had the greatest tensile strength, while the uniaxial one had the least. The tensile strength of triaxial and biaxial geogrids increased with the increase of tensile rates, while uniaxial decreased and then increased. The elongation at break of uniaxial and triaxial geogrids increased with increasing tensile rates, while biaxial increased and then decreased. With the increase of filling ratios, the tensile strength of geogrid increased and then decreased. For the line 45 angle printed geogrid, the elongation at break increased first and then decreased and finally increased. [ABSTRACT FROM AUTHOR]

Among biobased and biodegradable polymers, polylactic acid (PLA) is most widely used one. However, its poor mechanical properties need to be enhanced. In this study, PLA blend film with improved mechanical properties were developed without compromising any bio-content. For this, natural rubber derivative with acetate pendant group (ANR) and PLA blend films were prepared. First, natural rubber was epoxidized, and then partial acetylation was achieved by the ring-opening reaction of the epoxy groups. The epoxidation and the acetylation were examined by FTIR analysis. 1H-NMR spectrum revealed a 29% epoxidation and 8.25% acetylation degree. The Tg of natural rubber (−66°C) increased to −41°C and −31°C after epoxidation and acetylation, respectively. The compatibility of ENR and ANR with PLA was evident from the DSC results and Molau test. The morphology of PLA blend film containing 25 wt% of ANR (ANR25) was observed as well-dispersed fine droplets by SEM images. The tensile strength, elastic modulus, and yield strength of ANR25 were measured as 11.6 MPa, 397.3 MPa, and 6.9 MPa, respectively. These values are considerably higher than neat PLA film. Compared to reported studies on PLA toughening so far, increments in both the strength and elongation of ANR25 were observed by tensile tests. Moreover, highest toughness among all samples was determined as 18.8 MJm−3 for ANR25, which is 1.8 times higher than neat PLA. Thus, a strong and tough bio-based PLA blend was developed for film application such as packaging and sheeting. [ABSTRACT FROM AUTHOR]

Although the consequences of adhesive residues from post-consumer Poly(ethylene terephthalate) (PET) beverage bottles on the performance of recycled products are known, the quantitative effects of these adhesives are not well-stablished in the literature. Therefore, these residues were determined by gravimetry, and the adhesive content range from 200 to 2800 ppm in post-consumer PET bottles, depending on the drink filled. Through FTIR analysis, it was determined that the adhesives for bottles labelling are composed by poly(ethylene- co -vinyl acetate) (EVA). Based on these results, recycled PET with 0, 200, 700, 1500 and 3000 ppm of hot-melt EVA were processed in an internal mixer connected to a torque rheometer at 265°C for 10 min. Tensile tests indicate that 200 ppm of adhesive reduced PET tensile strength by 15%. Furthermore, when about 1500 ppm of adhesive is present, PET mechanical properties are reduced by 50%. Therefore, it is of utmost importance to warn the PET bottle production chain to reduce adhesive content used in labelling so that it should not exceed 200 ppm, if a high quality recycled PET is desirable. Graphical Abstract [ABSTRACT FROM AUTHOR]

This study aims to develop composite laminates for the manufacture of prosthesis socket with enhanced mechanical performance. Layered hybridisation of fabrics (i.e. glass, carbon, and Kevlar fabrics) is used to manufacture hybrid composite laminates by resin infusion via vacuum bagging method. The response of these materials to compression loading is investigated by using compression-loading testes and the load-bearing ability was examined by tensile strength tests. Moreover, finite element analysis has been carried out by using the Abaqus software to predict the compressive failure load and damage failure modes for all sockets samples. Experimental results revealed that the hybrid laminates exhibited more stability and higher absorbing energy compared to non-hybrid laminates during compressive loading tests. Furthermore, the hybridisation of fabrics layers can play key role for improving the tensile strength properties of hybrid composite laminates compared to composite laminates without hybridisation. The numerical simulation results of compressive failure load and damage failure modes are in accordance with experimental results qualitatively as well as quantitatively. [ABSTRACT FROM AUTHOR]

Discontinuous long-fibre (DLF) composites can be made with randomly oriented unidirectional pre-impregnated composite chips. High fibre volume fraction unidirectional fibre chips provide good mechanical properties to the DLF composite architecture, which enables this material to contribute to bridging the gap between continuous-fibre and randomly-oriented short-fibre composites. However, it is well known that unidirectional fibres have highly anisotropic in-plane behaviour, which causes weak points in the parts when chips are oriented at unfavourable angles. This can be problematic since chips are randomly oriented in DLF composites. To overcome this problem, this research utilizes woven fibre chips instead of unidirectional fibre chips to fabricate DLF composites. Woven fibres diminish the potential for weak points due to their more homogenized in-plane mechanical properties. For comparison purposes, compression moulded carbon/PEI samples were made from both unidirectional chips and 5HS woven chips. Bending and tensile tests following ASTM guidelines were performed to compare both types of fibre arrangement. The results show that woven fibre chips increase the mechanical properties of the DLF composites and reduce their variability. [ABSTRACT FROM AUTHOR]

Lempel–Ziv (LZ) complexity has been used predominantly in solving the information theoretic problems. However, its application is way beyond information theoretics. It has been used successfully in different biomedical applications. In this research work, this LZ complexity is used for identifying the damage modes in a plain weave fabric carbon fibre-reinforced polymer (CFRP) specimens tested at an elevated temperature. The acoustic signals generated during the tensile test of CFRP specimens at an elevated temperature are recorded. Their LZ complexity values are extracted and compared with different acoustic descriptors. When LZ complexity is used along with peak amplitude of the acoustic signal and its weighted peak frequency, it is able to distinguish the different damage sources of the signal. The acoustic signals with LZ complexity above 0.6 generally indicate their source as delamination or debonding of the fibres in the CFRP specimen. This multiparameter approach is more efficient in distinguishing the different damage modes in the CFRP specimens. [ABSTRACT FROM AUTHOR]

In additive manufacturing, fused deposition modelling (FDM) is one of the most often-used technologies. Polylactic Acid (PLA) is the most frequently applied polymer for prototyping or for real uses. This study mainly focuses on the mechanical properties of PLA parts printed with filament exposed to UV light to mimic the effect of recycled filament. Three radiation periods were studied, respectively, 24 h, 48 h and 72 h. Tensile tests were carried out to characterize the influence of building orientation (On flat/on-edge) and raster angles (0°, 45°, 90°, 0°/90°, −45°/+45°). Failure modes were also discussed. Printed specimens were subjected to water absorption to assess the mechanical properties in real application. Generally with the same raster angle, the interlayer structure of specimens manufactured in on-edge orientation has greater adhesion than the specimens in flat orientation. The results show that mechanical properties are lower in case of flat building orientation and the raster angle has the same trend in both orientations. Elsewhere, edge orientation exhibited lower water absorption thanks to the inwall that protected the printed part. UV radiation enhances the interface between printed layers for the lower period. The mechanical properties were affected by the degradation of the bulk material in the direction of 90°. [ABSTRACT FROM AUTHOR]

In this study, seven gradient plasticizing time at 200°C were set to explore the effects on Bally Flex fatigue of soft poly(vinyl chloride) (PVC). The results showed that the rotational rheometer was well used to characterize the plasticizing process of PVC paste. The optimum plasticizing temperature of soft PVC was about 180°C. Within a certain range of plasticizing time, the glass transition temperature of soft PVC decreased with the extension of plasticizing time, and the Bally Flex fatigue life was prolonged as the plasticizing time extended. When the plasticizing time was 105 s, the plasticization was nearly completed, which can be used as an optimum plasticizing time in terms of manufacturing efficiency and quality. When the plasticization time was 135 s, the degree of plasticization was the highest. The fatigue cycles of Bally Flex and breaking energy (W) at −20°C were 136,000 and 4850 J·m−3, respectively. It was concluded that Bally Flex fatigue life and W had a good positive correlation. Thus, the tensile test can be used as a simple approach to predict the Bally Flex fatigue life trend of soft PVC specimens. [ABSTRACT FROM AUTHOR]

In the present paper, the influence of tailored load introduction inserts applied to a bolt-loaded open-hole injection plate with different short glass fibre content is investigated. The tailored load introduction inserts made with a Tailored Fibre Placement (TFP) process, as well as open-hole injection plates without an insert were considered as reference samples. The samples were tested under tensile bolt-loading. The influence of the TFP-inserts on the load bearing properties of the open-hole injection plates was investigated. The test results show a huge increase of the load-carrying ability of the short-glass-fibre specimens when TFP-inserts are integrated. Moreover, the damage tolerance was dramatically improved as the specimens with integrated TFP-inserts did not fail abruptly and a residual strength higher than the strength of the test specimen without insert could be observed. However, the strength of the test specimen with integrated insert did not exceed the strength of the insert itself in most cases. [ABSTRACT FROM AUTHOR]

An agro-waste such as coffee beans has been used to generate cellulose particles. Coffee roast which is brown in color, was treated with 6% sodium chlorite solution, followed by alkali treatment. This chemically treated mass was subjected to acid treatment with 20% sulfuric acid. Cellulose microwhiskers were released. These micro particles were examined by an X-ray diffractometer (XRD). X-Ray diffraction study of these white cellulose particles and the residue showed a highly crystalline nature of the cellulose particles. The fourier transform infrared (FTIR) spectra were carried out to further investigate any structural changes after chemical treatment. The spectra of the treated powder showed lesser peak intensity at 1630 cm−1. This peak is related to the aromatic ring of lignin. Thus, indicating that the removal of aromatic rings of lignin and polysaccharides after hydrolysis process, simultaneously increases degree of crystallinity. Composites of epoxy resin with a conventional amide-type hardener reinforced with renewable materials were investigated in the presence of castor oil (CO). The renewable material was extracted from coffee beans using various chemical agents. The extracted renewable material has been incorporated into epoxy resin. The composites were evaluated by FTIR to check any interactions. The remarkable hint is the increased intensity of the peak located at 3941 cm−1 being assigned to the –NH2 of the amine cured epoxy. The increment in the intensity is being attributed to the enhanced degree of interaction between the multifunctional CO and the amine cured epoxy resin as mentioned earlier. Tests of tensile and impact strength properties were carried out and Izod impact was determined at room temperature. It has been found that the incorporation of CO has significantly increased the elongation at break. The impact resistance of the composites with CO has significantly increased as compared to the control and the samples without CO. Scanning electron microscopy (SEM) images were taken to assess the effects of reinforcement and homogenization of the composites. It was noticed that the incorporation of the CO has turned the topography of the samples to a smooth surface with respect to rugged phase of the samples without CO. [ABSTRACT FROM AUTHOR]

This study investigated the effects of FDM (Fused Deposition Modeling) process parameters on mechanical properties (tensile strength, elongation, and impact strength) of 3D (three-dimensional) printed PA12 (Polyamide12) samples using Taguchi method. In the experimental design (L8), four different layer thickness (0.1, 0.15, 0.2, 0.25 mm), extruder temperature (250 and 260°C), filling structure (Rectilinear and Full Honeycomb), and occupancy rate (25 and 50%) were determined. The tensile and impact strength test samples were printed with the FDM method. Tensile and impact strength of the test samples were carried out according to ISO 527 and ISO 180 test standards. The findings obtained from tests were analyzed and compared. As a result, the layer thickness is most effective factor for enhance the mechanical properties instead extruder temperature, occupancy rate, and filling structure. The optimum tensile strength of determined for process parameters (layer thickness, occupancy rates, filling structures and extruder temperature) were 0.25 mm, 50%, Rectilinear, and 250°C, respectively. The optimum impact strength of determined for process parameters (layer thickness, occupancy rates, extruder temperature, and filling structures) were 0.25 mm, 50%, 250°C, and Rectilinear, respectively. PA12 filament material can be used to printing for sleeve bearing due to their mechanical properties. It can be used in the production of many machine parts and components due to its tensile strength, impact strength resistance and damping properties. [ABSTRACT FROM AUTHOR]

Although several reports can be found in the literature about the recycling of plastic materials, only a few focus on recovering and molding them in a new process. Plastic material blends can be fabricated using several techniques, which allows the molding of a compound adaptable to each needed performance. This fact favors the recycling by allowing the use of mixed wastes without major processes, avoiding expensive treatments. This research work analyzes the mechanical properties of a material conformed by 100% recycled plastics: polyethylene terephthalate and low-/high-density polyethylene without previous separation or washing and drying pretreatments. Its macro and microscopic structure was studied and described, and formulations of different compound rates were analyzed. Mechanical resistance was around 60% of a material composed of virgin materials in compressive, flexural, and tensile strength tests. Its potential application to building components manufacture is analyzed. [ABSTRACT FROM AUTHOR]

In the present study, the effect of different ratios of GelMA concentration has been exhibited for wound dressing implementation by the electrospinning method using a new polymer combination of Gelatin methacrylate (GelMA)/Polycaprolactone (PCL)/Chitosan (CS). The nanofiber composites were fabricated due to their biocompatible, biodegradable, improved mechanical strength, low degradation rate, and hydrophilic nature to develop cell-mimicking, cell adhesion, proliferation, and differentiation. Different concentrations of GelMA were added to the PCL/CS solution as 5, 10, and 20 wt%, respectively, in the formic acid/acetic acid (7:3) solution. A photoinitiator was added to the solution for photo-crosslinking of GelMA. The influence of different solution concentrations (5, 10, and 20 wt%) on the structure's nanofiber production and fiber morphology was examined. SEM micrographs revealed that varied GelMA concentrations resulted in suitable and stable nanofiber composites. The average diameter of nanofiber composites grows as the GelMA concentration rises. FTIR, DSC, tensile test, degradation, and swelling test were evaluated. The results demonstrated that high mechanical strength, hydrophilic properties, and a slow degradation rate were observed with the presence and increment of GelMA concentration within the nanofiber composites. The antibacterial potential of GelMA/PCL/CS nanofiber composites was evaluated against P. aeruginosa and S. aureus using a disc diffusion assay. In vitro cell culture research was conducted by seeding NIH 3T3 fibroblast cells on nanofiber composites, proving these cells' high cell proliferation rate, viability, and adhesion. 10 wt% GelMA-based nanofiber composites were found to have great potential for wound dressing applications. [ABSTRACT FROM AUTHOR]

Arimatsu Narumi Shibori (thread-tying), which is a traditional craft, has a history of more than 400 years and has been handed down to artisans in Japan. Recently, the shortage of successors to artisans has emphasized the maintenance of this thread-tying technique. To achieve this, Arimatsu Narumi Shibori needs to be elucidated based on scientific knowledge using numerical analysis techniques, which has not been achieved so far. In this technique, the fabric is complexly deformed, and complex wrinkles are formed in it. One possible approach for modeling this fabric is the use of a shell element that does not have an element volume. As the tensile and bending stiffnesses of the shell element are evaluated using a single Young's modulus, the bending stiffness increases with the tensile stiffness. Therefore, unlike the deformation achieved by the actual fabric-tying, this fabric analysis model cannot achieve large deformation of the fabric. In this study, a tying analysis method is proposed to elucidate Arimatsu Narumi Shibori. In this method, the fabric is modeled using three layers of shell elements to reproduce the fabric behavior. The material properties of the three-layer structure are presented based on the tensile test, the bending test and the friction test. Using the proposed method, we could visualize the stress distribution and wrinkles in the fabric-tying and elucidate its breaking condition. [ABSTRACT FROM AUTHOR]

An experimental test program and companion analytical study were designed and conducted to gain understanding of the tensile failure mechanisms in asymmetrical tapered sandwich core structures at cold temperatures. Representative test coupons were subjected to a tensile load in an environmental chamber to induce foam tensile failure in the core. Finite-element modeling with a proposed maximum principal stress criterion was used to predict the failure loads of the tapered test coupon design at the test temperatures. The predicted failure loads were in good agreement with test results. An important finding is that the cure stresses in the foam are significant and should not be ignored. Additionally, the analysis correctly predicted the failure initiation location, which was verified using high speed photography during the tensile test. The study identified the critical failure regions of asymmetrical tapered sandwich core designs and the failure load dependence on the temperature gradient in the structure. [ABSTRACT FROM AUTHOR]

Polymers play an emerging role in modern engineering applications due to their comparatively low cost, low density, and versatile manufacturing. The addition of nano-sized fillers further enhances the polymer's properties but also induces a strong dependence on the resulting microstructure, particularly the matrix-filler interphase. Since an experimental characterization of this nano-sized interphase is extremely difficult, molecular dynamics (MD) simulations are used to study the effects at such small scales. However, MD's high computational costs usually limit the scope of a mechanical characterization. Therefore, this study presents the methodology and tools to generate and analyze samples of an efficient generic thermoplastic model. In this first contribution, we focus on the neat polymer and introduce a versatile and numerically stable self-avoiding random walker with adjustable linearity of chain growth. Moreover, we verify our equilibration procedure by preparing samples in liquid and solid state which behave physically sound. Finally, we perform uniaxial tensile tests with a maximum strain of 10 % to evaluate the mechanical properties. In the liquid case, the polymer chains are sufficiently mobile, such that the tensile stresses fluctuate only around zero, while the solid exhibits an almost linear elastic regime followed by a nonlinear part. This contribution forms the basis for a thorough mechanical characterization of polymer nanocomposites which we will address in future studies. The methodology and tools introduced are not limited to our generic polymer, but applicable to many coarse-grained models. [ABSTRACT FROM AUTHOR]

Biodegradable polyurethane with excellent mechanical property finds a lot of applications in the biomedical field. In this study, multi block copolymer poly(urethane-urea-amide) (PUUA) is prepared using polyethylene oxide, 1,6-hexamethylene diisocyanate and diamide (N1, N4-bis(6-aminohexyl)benzene-1,4-dicarboxamide (6T6) or N 1, N 6-bis(6-aminohexyl)hexanediamide (6A6)) by a method of solution/melt polymerization techniques. The polymer formation is confirmed by the 1H NMR spectroscopic method. Other techniques such as viscosity measurements, FT-IR, DSC, TGA, and biodegradability are used to characterize the synthesized copolymers. The hard segment crystallinity is an analyzed by FT-IR spectroscopy, it revealed that the 6T6 based polymer showed 70% of crystallinity. The synthesized copolymer shows three transitions in the DSC curve. The melting enthalpy of the hard segment depends on the amide unit employed in the polymerization process. These materials are fast crystallizing due to low under cooling value. This material has a very high thermal stability and stable up to 400°C. Tensile test confirms the strain induced crystallization of hard segment occurred in the PUUA. The biodegradability of the polymer depends on the pH and chain extenders. This type of materials can be a good candidate for tissue engineering application. [ABSTRACT FROM AUTHOR]

Mg-Zn-Ca-Mn materials micro-alloyed by Gd, Nd, Ce, and La rare-earth and Sr alkaline elements were developed. Optical and scanning electron microscopy, X-ray diffraction spectroscopy, tensile test, immersion, and electrochemical tests were applied to analyze microstructure, mechanical properties, and corrosion behavior. While the development of the equiaxed grain structures were observed in all the alloys, the Gd-containing alloy showed the smallest grain size and lowest fraction of second phases, which resulted in the highest yield and ultimate tensile strength of 310.0 ± 14.1 and 370.4 ± 41.6 MPa, respectively. Moreover, the corrosion studies also indicated the lowest rates in the Gd, and Nd-containing alloys, with the rates of 3.6 ± 2.5 and 3.9 ± 0.2 mm/y, respectively. The mechanisms of microstructure evolution, strengthening and corrosion behavior were discussed. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of medium manganese steel with a composition of 0.2C-5Mn-0.5Si-1.5Al (wt.%) were investigated, employing a two-stage heat treatment process. The microstructure following pretreatment comprised pearlite, martensite, and ferrite. Subsequent intercritical annealing resulted in the formation of retained austenite with varying morphology and composition. The filmy retained austenite transformed from pearlite exhibited a higher Mn content compared to the blocky retained austenite transformed from martensite, while also displaying a slower growth rate. Moreover, the filmy retained austenite exhibited superior thermal and mechanical stability. Tensile tests showed that the test steels not only obtained high strength (>1000 MPa) and high elongation (>30%), but the stress-strain curves also showed continuous yielding behaviour and a more reasonable ratio of tensile strength to yield strength. [ABSTRACT FROM AUTHOR]