Tensile Test Specimens Research Articles

Statistical in situ scanning electron microscopy investigation on the failure of oxide scales

AbstractOxide scales play a pivotal role in obstructing surface chemical and electrochemical reactions, hence hindering chemo‐mechanical effects such as liquid metal embrittlement of steels. Therefore, the critical conditions and failure mechanism of the oxide film are of major interest in the safe service of steels. Though in situ microscopic methods may directly visualize the failure mechanism, they are often challenged by the lack of statistically reliable evaluation of the critical conditions. Here, by combining in situ scanning electron microscopy with a tapered specimen tensile test in a single experiment, we uniquely achieve a mechanistic study with statistically reliable quantification of the critical strains for each step of the dynamic process of film rupture. This is demonstrated with the oxide films formed on a ferrite–martensite steel in liquid lead–bismuth eutectic alloy at elevated temperatures, with in situ results falling right into the predictions of the statistical analysis. Explicitly, the integrated experimental methodology may facilitate the materials genome engineering of steels with superior service performance.

Fracture Characteristics of EN AW 1200 Tensile Test Specimens Joined with FSW and SFSW Processes

The aim of the current study is to perform a preliminary analysis on specimens extracted from 4 mm sheets of EN AW 1200 alloys that were butt-joined using FSW and two SFSW processes. The purpose of this scientific investigation is to promote the suitability and advantages of new ecological joining processes by implementing SFSW in the automotive, naval, railway and aerospace industry. The papers authors performed destructive testing on specimens extracted from sheets joined with the above mentions processes, namely tensile strength test according to SR EN ISO 6892-1:2020. Researchers also performed topography analysis on samples extracted from the AW 1200 but-joined similar sheets using scanning electron microscopy – SEM, combined with energy dispersive X-ray analysis EDAX. Results from the tensile tests highlighted an improvement in the ultimate tensile strength of the welded butt-joint, if compared to regular FSW results. The highest tensile strength value resulted from the samples extracted from joints performed using the second version of SFSW process. Researchers also noticed that samples broke in the weld or transition area. There was also a change in the chemical composition of the sample performed using the first SFSW method, namely, a high concentration of oxide appeared (≥18%), leading to the conclusion that the module used induces rapid oxidation of joints. Experimental data doesn’t comply with automotive, railway, naval and aerospace-imposed compliances, thus further investigations should be done to improve the application of the technology.

The scale factor effect on Young’s modulus of steel specimens determined by tensile tests

The modulus elasticity (or Young’s modulus) is considered to be a rather stable physical and mechanical characteristic of metallic materials being a weak function of the chemical composition and structure. However, the temperature and anisotropy can be referred as the main factors affecting the Young modulus. Scanty data on the scale factor effect on Young’s modulus are sometime even contradictory. We present the results of studying the impact of the scale factor on Young’s modulus of steel 45 determined by the tension of cylindrical tensile specimens with different initial diameters on an Instron 8801 machine with a movable traverse speed of 0.1 mm/min at room temperature. An extensometer and a digital image correlation (DIC) method were used to measure elastic deformations. Both methods showed fairly close results during tensile testing of specimens with equal diameters. DIC method made it possible to measure elastic deformations on small-size specimens on which it was impossible to fix the extensometer. A decrease in the Young modulus with an increase in the specimen diameter has been revealed. Graphical dependences of the Young modulus on the specimen diameter and cross-sectional area have been obtained. Possible reasons for the decrease in the Young modulus under the influence of the scale factor have been indicated. A decrease in the specific surface area and specific surface energy, an increase in the deformable volume, and a decrease in the strain rate at a constant movable traverse speed are among the main reasons. The decrease in Young’s modulus under the influence of the scale factor must be taken into account in strength calculations and in assessing the residual life of large-scale parts and structures with relatively large cross sections and wall thicknesses.

Determination of the elastoplastic properties of Ti-6Al-4V alloy manufactured by electron beam melting

PurposeThis study aims to evaluate and assess the elastoplastic properties of Ti-6Al-4V alloy manufactured by Arcam Q20 Plus electron beam melting (EBM) machine by a tensile test campaign and micro computerized tomography (microCT) imaging.Design/methodology/approachASTM E8 tensile test specimens are designed and manufactured by EBM at an Arcam Q20 Plus machine. Surface quality is improved by machining to discard the effect of surface roughness. After surface machining, hot isostatic pressing (HIP) post-treatment is applied to half of the specimens to remove unsolicited internal defects. ASTM E8 tensile test campaign is carried out simultaneously with digital image correlation to acquire strain data for each sample. Finally, build direction and HIP post-treatment dependencies of elastoplastic properties are analyzed by F-test and t-test statistical analyses methods.FindingsModulus of elasticity presents isotropic behavior for each build direction according to F-test and t-test analysis. Yield and ultimate strengths vary according to build direction and post-treatment. Stiffness and strength properties are superior to conventional Ti-6Al-4V material; however, ductility turns out to be poor for aerospace structures compared to conventional Ti-6Al-4V alloy. In addition, micro CT images show that support structure leads to dense internal defects and pores at applied surfaces. However, HIP post-treatment diminishes those internal defects and pores thoroughly.Originality/valueAs a novel scientific contribution, this study investigates the effects of three orthogonal build directions on elastoplastic properties, while many studies focus on only two-build directions. Evaluation of Poisson’s ratio is the other originality of this study. Furthermore, another finding through micro CT imaging is that temporary support structures result in intense defects closer to applied surfaces; hence high-stress regions of structures should be avoided to use support structures.

Evaluation of the mechanical properties of polyamide 12 regarding different percentages of reused material in the selective laser sintering process

PurposeAdditive manufacturing (AM) has been one of the most highlighted processes of the last few years. AM prints complex parts and items from 3D files regarding different materials, such as polymers. Moreover, there are different AM techniques available for polymers, such as selective laser sintering. In the SLS technology, polyamides 11 and 12 lead 88% of the market. These materials are high-cost and use an average of 50% of virgin material at each printing. It is possible to use lower rates of virgin material, but at least 30% is recommended. Low rates of virgin material decrease mechanical properties.Design/methodology/approachThis study aims to evaluate the influence on the mechanical properties of the percentage of reused PA12 in parts manufactured by the SLS process. The specimens of PA12 were manufactured with a percentage of virgin/reused polymer of 50/50, 40/60, 30/70, 20/80 and 10/90. We considered three distinct printing directions to compare the mechanical properties of the specimens: horizontal, perpendicular and vertical.FindingsThe results showed that when the percentage of reused material increases, the tensile strength limit (TSL), flexural strength limit and Shore D hardness decrease. Another aspect visualized was the fragile behavior presented in the vertical specimens. In addition, DSC analysis indicated a 2% reduction of crystallinity. Scanning electron microscopy images revealed spherical voids and unfused particles of PA12 at the fracture of tensile test specimens. The material thermal history and unfused particles could decrease the material properties.Originality/valueWe observed that the mechanical properties, such as the TSL, flexural strength limit and hardness, decrease as the percentage of reused material increases. In addition, the process presented a printing-direction dependence, where the vertical direction presented as the more brittle between the ones used.

Effect of machining operations on mechanical properties, surface integrity and corrosion resistance of tungsten heavy alloy

Tungsten heavy alloys (WHAs) are metal-metal matrix composites which are suitable candidates for defence and nuclear applications. In order to meet the geometric complexity and dimensional tolerance of products made with these WHAs, secondary machining operations are necessary. The effect of three set of machining operations (wire EDM, rough turning and finish turning) on mechanical properties, surface residual stress, surface and sub-surface hardness and corrosion resistance are explored in this work. Uniaxial tensile test specimens were prepared with two different sets of feed rate and depth of cut corresponding to rough and finish turning. For the specimens prepared with harsher conditions around 20% reduction in elongation was noticed though there were no significant changes in yield strength or ultimate tensile strength. Finish turning resulted in a surface residual stress in the order of 700 MPa, compressive in nature. Though compressive, the magnitudes of the surface residual stress were significantly reduced for the other two operations. Turning operations were found to work harden the surface while WEDM caused a reduction in surface hardness. Subsequent variations in the subsurface hardness were also observed reaching upto a depth in the range of 50–150 µm. Surfaces produced under different machining conditions were exposed to chloride solution to examine the impact of surface integrity on the corrosion behaviour and the correlation among the two are investigated. Rough turned surfaces and wire EDM surfaces have shown reduced corrosion resistance.

The Characterization of Mechanical and Chemical Properties of Recycled Styrofoam Waste Employing Extrusion Process

<p><em>Styrofoam waste is a polystyrene plastic-based waste in the form of foam with low density. Scavengers or recyclers are not interested in receiving styrofoam waste because of its light density which makes it ineffective in transportation and storage. Styrofoam waste can actually be converted into solid polystyrene products through a thermal-extrusion process but data regarding the optimum operating temperature and the characteristics of the resulting solid polystyrene products are not yet available. The purpose of this study was to investigate the properties of solid polystyrene products resulting from recycled styrofoam waste and determine the optimum temperature of the thermal-extrusion treatment process to be compared with the characteristics of the original polystyrene based on the results of tensile and impact tests. In this study, the processing was carried out using the thermal-extrusion method; Styrofoam is melted and extruded into a mold to produce polystyrene solids. The research was carried out with variations in extrusion temperature at 180°C, 200°C, and 220°C. The polystyrene solids are then molded into tensile and impact test specimens by injection molding. The results showed that the optimal extrusion temperature was 200°C with tensile and impact strength values of 27.55 MPa and 1,069 j/m2, respectively. Compared to the original polystyrene, the tensile strength value is 25.3% lower and the impact strength value is 29.5% lower. The decrease in the tensile and impact strength values is due to the shortening of the molecular bonds in the recycled polystyrene during the thermal-extrusion treatment process. Even though the tensile strength and impact are still lower, the use of styrofoam waste using the thermal-extrusion method has the potential to be developed at the production and commercialization stage because the resulting product has good economic value and can also reduce the use of original polystyrene and at the same time can solve the problem of styrofoam waste.</em></p>

Solid-State Additive Manufacturing of AA6060 Employing Friction Screw Extrusion Additive Manufacturing

AbstractSolid-state additive manufacturing constitutes a worthwhile alternative for many precipitation-based aluminium alloys that cannot be processed through fusion-based approaches due to metallurgical problems. In this work, the newly developed solid-state friction screw extrusion additive manufacturing (FSEAM) approach has been employed to study the processability of AA6060 T6 as a function of the printing velocity. Various wall-like builds were fabricated at printing velocities of 100 mm/min to 250 mm/min by deposition of 50 layers of 1 mm thickness, 14 mm width, and 150 mm length. No major defects were observed in cross section, and the microstructure showed equiaxed grains with an average size of 2–4 μm for all builds. Promising mechanical properties were obtained for all tensile test specimens extracted in the deposition direction of the layers. For specimens extracted in the build direction, only the builds fabricated with sufficiently high normal force to ensure proper bonding between successively deposited layers showed similar results to the deposition direction. The relatively high temperatures obtained during fabrication led to the dissolution of strengthening precipitates for the 150–250 mm/min samples as indicated by serrated yielding effects. Post-manufacturing heat treatment of these samples was successful, partially restoring the feedstock hardness.

Additive Manufacturing of Locally Weakened Parts to Obtain a Designed Fracture

Today, the additive manufacturing (AM) approach has led to profound changes in part and process design, enabling previously impossible material properties. With the freedom to create the material as components are built layer by layer, AM has permitted precise spatial control of the material properties in manufactured parts. In this work, an original approach is proposed to locally control component and process design and create intentionally weakened regions with designed fracture, which paves the way to tuneable mechanical properties. Tensile tests of specimens with embedded weakened area of various geometries are used to verify the feasibility of a-priori-designed fracture modes and to characterise the variation in material behaviour. The results show that an ad hoc design of the artificially weakened areas is effective for predictable breakage, with load and strain being the precursor for active control of the mechanical behaviour. The attainability of a quantitative relationship between the defect and the mechanical response is exemplified by the fact that, e.g. for a flat geometry, the maximum stress and strain are reduced by half when the thickness of the weak region is doubled.Graphical abstract

Thermomechanical Properties of Neutron Irradiated Al3Hf-Al Thermal Neutron Absorber Materials.

A thermal neutron absorber material composed of Al3Hf particles in an aluminum matrix is under development for the Advanced Test Reactor. This metal matrix composite was fabricated via hot pressing of high-purity aluminum and micrometer-size Al3Hf powders at volume fractions of 20.0, 28.4, and 36.5%. Room temperature tensile and hardness testing of unirradiated specimens revealed a linear relationship between volume fraction and strength, while the tensile data showed a strong decrease in elongation between the 20 and 36.5% volume fraction materials. Tensile tests conducted at 200 °C on unirradiated material revealed similar trends. Evaluations were then conducted on specimens irradiated at 66 to 75 °C to four dose levels ranging from approximately 1 to 4 dpa. Tensile properties exhibited the typical increase in strength and decrease in ductility with dose that are common for metallic materials irradiated at ≤0.4Tm. Hardness also increased with neutron dose. The difference in strength between the three different volume fraction materials was roughly constant as the dose increased. Nanoindentation measurements of Al3Hf particles in the 28.4 vol% material showed the expected trend of increased hardness with irradiation dose. Transmission electron microscopy revealed oxygen at the interface between the Al3Hf particles and aluminum matrix in the irradiated material. Scanning electron microscopy of the exterior surface of tensile tested specimens revealed that deformation of the material occurs via plastic deformation of the Al matrix, cracking of the Al3Hf particles, and to a lesser extent, tearing of the matrix away from the particles. The fracture surface of an irradiated 28.4 vol% specimen showed failure by brittle fracture in the particles and ductile tearing of the aluminum matrix with no loss of cohesion between the particles and matrix. The coefficient of thermal expansion decreased upon irradiation, with a maximum change of -6.3% for the annealed irradiated 36.5 vol% specimen.

Effect of bio-mineral oil blend quenchant on the mechanical properties of carburized mild-steel

In this study, the effect of bio-mineral oil blend quenchants on the mechanical properties of carburized mild steel was experimentally studied and reported. The tensile, hardness, impact, and microstructural test specimens were prepared in line with ASTM standards. Prepared specimens were then buried in a 50:50% ratio mixtures of eggshell/date-seed particulates as carburizing medium in a sealed packed cylindrical crucible. The carburization was then carried out in a muffle furnace at 950 oC for 3 h soaking time at 5 °C/min heating rate and thereafter quenched in different percentage blends of bio-mineral oils. Before the mechanical test and microstructural examination, samples were tempered at 200 oC for 1 h.Results from the experimental findings revealed that water and bio-mineral oil blend quenchants significantly influenced the mechanical properties and microstructure of carburized mild steel in varying degrees depending on the quenching media. Specimen quenched in 100% groundnut oil yielded the maximum yield tensile strength (805.43 MPa) and hardness at the surface edge (173.8 HV) equivalent to 106.7 and 87.66 percentage increment however, the best combination of mechanical properties (tensile strength 738.66 MPa, strain 17.12%, hardness 169.5 HV and impact strength 51.1 J) was obtained in the specimen quenched in 60/40% groundnut oil and SAE40 oil blends respectively. The enhancement in the mechanical property was due to the grain refinement in the microstructure of the bio-mineral oils quenched specimen. The 60/40 groundnut/SAE40 oil blend is therefore recommended for metallurgical heat treatment of mild steel for critical industrial applications.

A study on the effect of plasticity on the measurement of residual stresses using ultrasound technique

Residual stresses can have detrimental effect on the life cycle of engineering components and can affect the accuracy of the fatigue life prediction models. Accurate measurement of these stresses are therefore crucial. . However, destructive and semi-destructive methods of measuring residual stresses often cause damage to the components. In contrast, the non-destructive ultrasonic method allows for intact measurement of residual stresses even, in situation where portability is not feasible. Various waves can be utilized in the ultrasonic method for measuring residual stresses. In this study, longitudinal critically refracted (LCR) waves were employed due to their higher sensitivity, larger scanning area, and lower sensitivity to texture effect, making them preferable over other waves. The purpose of this study was to investigate the influence of plasticity on the measurement of residual stresses using the ultrasonic method. To achieve this, two stainless steel disks were subjected to quenching at temperatures of 300 °C and 700 °C to induce different levels of residual stresses and plasticity. The material properties of the disks were determined through standard tensile tests to facilitate numerical simulations. Tensile test specimens were extracted from the initial sheet to measure the yield stress and modulus of elasticity. The coefficient of acoustoelasticity, was determined by subjecting the tensile test specimens to different stress levels and recording the wave flight time. The coefficient of acoustoelasticity for stainless steel 316Lwas obtained using the slope of and (E(t-t0))/t0,. Residual stresses were experimentally measured using both the ultrasonic method and the center-hole drilling method, and the results were compared with those obtained from numerical analyses. The findings from center-hole drilling method, ultrasonic method, and numerical simulation were then compared and discussed. Different levels of plasticity were considered, and the accuracy of measuring residual stresses was analyzed and evaluated.

Mechanical behavior of recrystallized and precipitation-hardened Inconel X-750 before and after helium-implantation and proton irradiation

An accelerated irradiation method using ion irradiation of recrystallized and precipitation-hardened Inconel X-750 has been used to study the effect on mechanical properties and microstructure of: (i) atomic displacement damage; and (ii) helium implantation. The atomic displacement damage was produced by irradiation with 5 MeV protons at 400 °C and varied from about 0.1 dpa at the surface to 1 dpa at a depth of about 75 μm in a tensile test specimen that was 80 μm thick. Helium implantation was conducted at 450 °C using a range of He ion energies to obtain a relatively uniform distribution within an 80 μm thick tensile specimen with peak levels of about 3000 appm helium. The tensile specimens were tested in uniaxial tension at room temperature using a conventional load frame to separately determine the effect of irradiation damage and helium-implantation on mechanical properties. For both cases the yield and ultimate tensile strength increased, and the ductility decreased, even though the atomic displacement damage and [He] concentrations were low and non-uniform. TEM examination showed that the increased strength is attributed to point defect clusters in the form of loops for the proton irradiated material and He-stabilized cavities for the He-implanted material.

Improvement of the tensile properties of laminated composites reinforced with Heli‐Coil forms of carbon nanotubes

AbstractThe traditional composite laminated structures suffer from the absence of reinforcements in the thickness direction between the laminae and microfibers, which will result in poor interaction between the laminae, individual microfiber filaments, and the resin. In addition, out‐of‐the‐plane properties are generally dominated and controlled by poor matrix properties (e.g., mechanical, electrical, and thermal). Most prior investigations were focused on the use of straight carbon nanotubes (CNTs), graphene, or nanomaterials in particle forms to improve the resin properties. Our previous research has shown that CNTs with helical (Heli‐Coil) geometries (HCNTs) are more effective as a nanoscale reinforcement to improve the properties of polymeric resins. Because of their inertness, the interfacial bonding between CNTs and the resin is generally weak, and they can be easily pulled out of the resin (inefficient load transfer) if the CNTs are in their straight forms. However, the helical geometries of HCNTs can provide unique mechanical‐interlocking mechanisms between the constituents that can substantially improve their effectiveness as a nanoscale reinforcement, leading to improvements in composite performance, properties, and multifunctionality. In this research, HCNTs at low concentrations below 0.1 wt% were processed and then used to fabricate nanocomposite laminates. Tensile test specimens were carefully prepared following the ASTM D3039/D3039M standard and then tested, analyzed, and evaluated. Additionally, the fractured test specimens were inspected and analyzed using optical and 3D scanning laser‐confocal‐microscopy imaging. The test results showed improvements of 12.3%, 11.3%, and 17.5% for the tensile strength, modulus, and strain‐to‐failure, respectively. In conclusion, traditional fiber‐reinforced composites can considerably benefit from the helical forms of HCNTs.Highlights The helical geometry of CNTs (HCNTs) is more effective for composite reinforcement. HCNTs provide unique interlocking mechanisms between the composite constituents. HCNTs can considerably improve the multifunctional characteristics of the composites. HCNTs can considerably improve the tensile properties of composite laminates. Traditional composites can substantially benefit from the helical forms of HCNTs.

Environment-Induced Crack Initiation and Early Stages of Crack Growth in Aluminum Alloys, Part 2

A second group of ‘state-of-the-art’ contributions [1-4] by invited researchers on the ‘Environment-Induced Crack Initiation and Early Stages of Crack Growth in Aluminum Alloys’ appear in this issue, complementing the papers published in the January 2023 issue of Corrosion [5-8]. The second section, presented herein, includes an overview of the experimental study of the initiation of environment-induced cracking (EIC) in aluminum alloys conducted since the 1950’s [1], showing crack initiation typically dominates the total life experienced during both service-life for structural applications and for smooth tensile test specimens subjected to conventional standard EIC testing. The review also reveals, although research conducted over the last 30 years almost exclusively focus on EIC propagation, there are notable exceptions worthy of re-evaluation and further study using modern in-situ advanced experimental techniques, paying particular attention to the roles of creep, crack-arrest and surface conditions during EIC initiation, paying particular attention the immediate sub-surface layers. The three additional papers in this collection are experimental studies. One investigates the significant differences in EIC initiation observed from fatigue pre-cracks and corrosion-induced fissures under controlled electrochemical conditions in a sensitized AA5456-H116 fracture mechanics test specimen exposed to a marine environment [2]. The final two papers involve testing conducted on high Zn-content Al-Zn-Mg-Cu 7xxx series alloys [3, 4]: one involves two commercial thick pate commercial high Zn content new-generation alloys [3], AA7449 and AA7085 in the T7651 temper and provides a detailed description of EIC initiation and its transition to long-crack growth during exposure to water vapor at 70 °C. Information gleaned from in-situ time-lapse, optical imaging over large areas has enabled the exact initiation sites to be identified and investigated with high-resolution fractographic studies. In the final paper [4] based on the deformation and fracture behavior of a high Zn-content Al-Zn-Mg-Cu 7xxx alloy observed in situ using synchrotron radiation X-ray tomography, it is proposed the dispersion of Mn-based second-phase particles may offer a novel approach for preventing hydrogen embrittlement in 7xxx series aluminum alloys.

Temperature-Controlled in-situ Tensile Tests of Polymer Tape with Single Particles

X-ray Computed Tomography (CT) combined with mechanical testing can deliver great insights in the damage mechanisms of polymers. Depending on the application area of the polymer, temperatures can be very high or low – leading to a different performance compared to room temperature. In this study, the influence of the temperature on damage mechanisms of a single particle in a polymer matrix should be investigated. Thus, three polymer tensile test specimens (length 30 mm; width 10 mm) – each containing a single particle – were cut out of a tape with a thickness of 0.5 mm and tested at various inspection temperatures. CT measurements were performed with the RX Solutions Easytom 160 laboratory CT device with a voxel size of (3 µm)³. Each specimen was scanned twice, namely at 0% strain and 30% strain. As inspection temperatures 0 °C, 22 °C and 60 °C were chosen. It is shown that temperature can have a great impact on the performance and damage mechanisms of a polymer, especially if a particle is present in the polymer matrix.

Investigating the thermal and mechanical properties of novel LDPE/TiO2 and LDPE/TiO2/CNT composites for 3D printing applications.

The development of new materials is essential for advancing technology and improving the quality of life. With new materials, we can create products that are stronger, more durable, and more efficient. The ongoing research and development of new materials for 3D printing applications continue to drive innovation in various fields, leading to improved products and processes with great benefits. The main goal of this work was to produce a functional filament with a 1.75-mm diameter that may be used for 3D printing. Composite materials were prepared using a low-density polyethylene (LDPE) resin as polymer matrix, and titanium dioxide (TiO2) and carbon nanotubes (CNT) as fillers in various ratios. Up to 15 wt% of TiO2 and 0.25 wt% of CNT were added. Some of the greatest difficulties with high filler content composites are achieving good homogeneity, and in the case of the 3D printing, greatest difficulties are producing the filament with a specific and stable filament diameter. During the 3D printing itself, the fillers can also often cause the nozzle clogging. This paper reports findings of thermal and mechanical properties of the LDPE/TiO2/CNT composites which are significant for the 3D printing process and the applicability of the composite materials. All of the planed composite materials are successfully prepared and 3D printed into the tensile test specimens. The melting point shift caused by the addition of fillers did not show consistent pattern at differential scanning calorimetry, as all of the samples had melting temperatures around 113.5 ± 1.4 °C. The addition of filler, according to the TGA, increased the threshold temperature for the material decomposition, in case of TiO2 5.4 °C increase, while TiO2 and CNT combination increased the threshold temperature for 6.8 °C. The results of the tensile test show a general increase trend with addition of TiO2 filler but do not show to a trend for the tensile strength as a result of the addition of CNT filler. The sample with highest TiO2 filler ratio of 15% (LDPE 15T0C) showed the greatest tensile strength of 14.5 MPa, compared to the 13.0 MPa of pure LDPE. The sample with 5% of TiO2 filler and 0.1% of CNT filler (LDPE 5T0.1C) showed the greatest elongation of 73.9%, compared to the 68.9% of pure LDPE.

THE EFFECT OF VARIATION OF TEMPERATURE ON PULL TEST OF FIBERGLASS FIBER COMPOSITE MATERIALS WITH VACUUM ASSISTED RESIN INFUSION (VARI)

To determine the effect of temperature variations on mixing fiberglass composite resin materials with the vacuum infusion method in the Tensile test. To determine the effect of the lowest and best temperature variations on mixing fiberglass composite resin materials with the vacuum infusion method on fotomikro. Variation fixed resin; polyester, fiber; fiberglass, vacuum; vacuum Infusion. Variable temperature of mixing resin 30˚C, 40˚C, and 50˚C. In this study, the vacuum infusion method was used, where the researcher made a specimen using the Vacuum Assisted Resin Infusion (VARI) process. In the VARI process, dry fiber is placed between the fixmold and the plastic bag, then the resin is injected after the space inside the plastic bag is under low pressure and the process continues until all parts of the fiber are wetted by the resin. After the specimen is made, then a tensile test is carried out to determine the mechanical strength of the specimen being tested. Then analyze the tensile test data using the equations used and displayed in the form of graphs and tables. This study was used to determine the effect of fiberglass composites with the vacuum infusion method on the tensile strength test. results of Tensile testing of fiberglass fiber composites and temperature variations of 30°C, 40°C, and 50°C. From the table it can be seen that the specimen with the best performance is found in the specimen with a temperature variation of 50°C, where the load that can be withheld reaches 508.56 kgf. So for maximum tensile strength it produces 11.07 MPa. Then on the specimen with a temperature variation of 40°C the best performance is 361.95 kgf. So for maximum tensile strength it produces 8.46 MPa. In specimens with a temperature variation of 30°C the best performance is 251.10 kgf. So for a maximum tensile strength of 5.67 Mpa. The average yield strength shows the results of the Tensile test of each variation, totaling 9 specimens. For the highest yield strength, a value of 9.67 MPa was obtained at a temperature variation of 50°C and for the lowest yield strength, a value of 4.13 MPa was obtained at a temperature variation of 30°C. Tensile test specimens have results where the highest yield strength or yield strength is obtained by specimens with a temperature variation of 50°C and as the stress increases, the yield strength value increases, and for the tensile strength of the material or tensile strength which has the highest value in the test, the specimens with 50°C temperature variation. Thus, the effect of temperature treatment is significant on the increase in tensile strength, but if the temperature is 30°C it will decrease the tensile strength, as at 30°C it produces an average tensile strength of 4.62 MPa. The results of the microphoto test show that at a temperature variation of 50°C there are a few voids while the 30°C variation has too many voids. Micro photo testing aims to determine the content in the composite.

Experimental Validation of a Micro-Extrusion Set-Up with In-Line Rheometry for the Production and Monitoring of Filaments for 3D-Printing.

The main objective of this work is to validate an in-line micro-slit rheometer and a micro-extrusion line, both designed for the in-line monitoring and production of filaments for 3D printing using small amounts of material. The micro-filament extrusion line is first presented and its operational window is assessed. The throughputs ranged between 0.045 kg/h and 0.15 kg/h with a maximum 3% error and with a melt temperature control within 1 °C under the processing conditions tested for an average residence time of about 3 min. The rheological micro slit is then presented and assessed using low-density polyethylene (LDPE) and cyclic olefin copolymer (COC). The excellent matching between the in-line micro-rheological data and the data measured with off-line rotational and capillary rheometers validate the in-line micro-slit rheometer. However, it is shown that the COC does not follow the Cox-Merz rule. The COC filaments produced with the micro-extrusion line were successfully used in the 3D printing of specimens for tensile testing. The quality of both filaments (less than 6% variation in diameter along the filament's length) and printed specimens validated the whole micro-set-up, which was eventually used to deliver a rheological mapping of COC printability.

Influence of Graphite Particles on the Mechanical and Wear Characterization of Al6082 Alloy Composites.

In the current study, a two-stage stir cast process was used to produce Al6082 reinforced with sized graphite particulates, and the material's mechanical and tribological properties were analyzed. The graphite content in the Al6082 alloy was increased from 2 to 6% in steps of 2 wt %. The impact of graphite addition to Al6082 was evaluated using microstructural micrographs, hardness test, tensile test, and wear test outcomes. The matrix alloy's microstructure and particle distribution were analyzed using scanning electron microscopy and energy-dispersive spectroscopy. The microstructure of Al6082 shows that the reinforcement particles are evenly distributed throughout the matrix. Although the hardness of metal-matrix composites was slightly reduced when graphite was added at concentrations of up to 6 wt %, the material's tensile strength and wear resistance were significantly improved. Micrographs taken by a microscope were used to examine the fractured surfaces of tensile test specimens. Wear experiments were performed using a conventional pin-on-disc tribometer to examine the tribological properties of both unreinforced matrix and graphite composites. With the addition of 2, 4, and 6 wt % of graphite particles, the composites' wear resistance was significantly improved. Wear of alloys and their composites was analyzed to determine how load and sliding speed impacted wear loss.