Tensile Test Specimens Research Articles

Tensile Properties of Epoxy Composites Filled With Graphene Nanoplatelets and PUF Microcapsules

AbstractThis work evaluates the effect of poly(urea‐formaldehyde) (PUF) microcapsules filled with aminated polydimethylsiloxane (PDMS‐a), a self‐healing agent, on the tensile properties of epoxy composites reinforced with graphene nanoplatelets (GNP). The microcapsules are produced by interfacial polymerization and later are infiltrated with the healing agent (PDMS‐a). GNP are dispersed in epoxy resin using sonication, followed by the addition of hollow or filled PUF microcapsules to the system, using mechanical stirring, just before the addition of the curing agent (hardener). The mixture is then cast in soft molds to produce specimens for tensile tests. The results show that the presence of 1 wt% GNP changes the properties of the composites with an improvement in tensile strength and modulus, which achieves 37.4 MPa and 2.8 GPa, respectively, in comparison with neat epoxy and specimens containing just microcapsules. The addition of 2 wt% GNP, however, impairs these properties, with tensile strength and Young's modulus decreasing to 24.9 MPa and 2.3 GPa, due to the presence of GNP agglomerates. The presence of the microcapsules, however, decreases the immediate (no self‐healing) tensile performance of the composites.

Implementation of miniature tensile specimens in mechanical properties assessment of directed energy deposited Ti-6Al-4V: As-built and heat treated

Within the last two decades, additive manufacturing (AM), a. k.a. 3D printing, has provided promising solutions for producing near-net-shape components with intricate geometries. From the material perspective, titanium alloys, one of humankind's most essential structural materials, are being considered the first candidate for AMed parts due to their unique characteristics in strength-weight-corrosion combinations. However, measuring the mechanical properties of designed geometry remains a challenge due to the ineffectiveness of conventional standard tensile specimens in assessing the site-specific and intricate geometries. In AM, the current approach often consists of evaluating standard-sized samples with the assumption that components with complex geometries possess comparable mechanical properties, even though they may have undergone different thermal processes in various situations. Hence, combining the microstructural characterization, this study aims to investigate the mechanical properties of direct energy deposition (DED) Ti-6Al-4V through a newly designed miniature tensile test (M-TT) specimen. The as-built specimen showed ultimate tensile strength (UTS) of ∼1305.3 MPa and elongation of ∼8.6 % with the mixed basketweave and α-colony microstructure. However, the DED Ti-6Al-4V specimen heat-treated at 850 °C exhibited the highest average elongation of ∼13.2 % and decent UTS of ∼1240.3 MPa with the α+β microstructure.

Improvement of mechanical performance via interfacial strengthening of carbon fiber‐epoxy reinforced hybrid laminate by incorporation of functionalized graphene nanoplatelet interphase

AbstractThis study is an attempt to develop high‐quality hybrid composites via functionalization (for homogeneous distribution) of the graphene nanoplatelets (FGNP) and then doping to carbon fiber reinforced especial aviation epoxy matrix (Araldite LY5052) via vacuum bagging molding (VBM). The utilized materials were characterized by UV–Vis spectroscopy, tensile, impact, hardness tests, and fracture mode analysis using a scanning electron microscope (SEM). The results revealed a 92% (502.5 MPa) and 85% (490 MPa) improvement in tensile strength values by doping the 1 and 1.5 wt% FGNPs, respectively. There was an improvement in impact strength with the addition of FGNP; a 28% (3.23 J/mm2) increase was achieved in the nanocomposite with 1 wt% FGNP added, and there was a decrease again in the nanocomposite with 1.5 wt% FGNP added. However, it was still 12% (2.83 J/mm2) better than the neat composite. In addition, the results of examining the fractured surface structures of the impact and tensile test specimens were compatible with these results. It reveals a significant separation of fiber‐matrix bonds with 1.5 wt% FGNP contribution. While tensile and impact strengths peak at 1 wt% FGNP value and decrease afterward, hardness values increase in parallel with the increase in FGNPs.Highlights Composites were developed by functionalized graphene nanoplatelets (FGNP). The fiber‐matrix interface was strengthened with FGNP interphase. A 92% tensile strength increase was achieved with 1 wt% FGNP additives. 28% in impact strength and 55% in hardness increase by 1 wt% FGNP. The morphology confirmed that the FGNP interphase filled the interface.

An investigation of clay percentage variation on composite materials sustainability identification by digital image correlation

ABSTRACT The study focuses on stress and strain evaluation of composite resin material with the reinforcement of clay in the glass-reinforced epoxy composite (GREC). The strain measurement used the DIC technique. The tensile test specimens were prepared from the laminate sheets as per ASTM D638 standard. The influence of nano clay weight percentage such as 2.5%, 3.5%, and 4.5% during preparation of GREC is studied in the article. The fibre orientation angles are 90°, and the fibre volume percentage is 45%. Hand lay-up methods are used to prepare the composite resin material. The samples were tested as per the standardised procedures. The specimen rupture at a localised strain reached a maximum value of 0.01293, 0.01571, and 0.0143 with 2.5%, 3.5% and 4.5% Nano clay, respectively. The material behaviour in terms of major strain (εyy), Poisson’s ratio (µ) and thickness strain (Δt) is evaluated at the gauge length of the specimen. DIC strain measurement clearly demonstrates the 3.5% percentage of clay addition as it yields better results as elastic modulus and tensile strength have improved. The composite resin with clay addition could be used in various applications, such as low-cost housing, structural works, medical devices, automotive panels, etc

Micromechanical testing and microstructure analysis of as-welded and post-weld heat-treated Ti-6Al-4V alloy

The microstructural evolutions and variations in mechanical performance of electron beam welded (EBW) Ti-6Al-4V (Ti64) alloy have been investigated. The effects of heat treatment on the microstructure of welded samples have been studied after post-welding solution treatment and ageing. The martensitic phase α′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\alpha }{\\prime}$$\\end{document} has been confirmed using transmission electron microscopy (TEM). Electron backscatter diffraction (EBSD) has been used to investigate the phase and grain morphology. Results showed that the martensitic α′ phase coarsened, the size of heat-affected zone (HAZ) changed and grains in the base materials (BMs) had grown after the post-weld heat treatments (PWHT). The tensile behaviour of electron beam welded Ti64 has been investigated using in situ tensile testing monitored by optical microscopy. The deformation and failure were directly revealed during the in situ tensile process. Results showed that the EBW Ti64 samples have different failure locations after receiving different post-weld heat treatments. The relationship between the post-weld heat treatments, microstructural evolution and mechanical properties of EBW Ti64 were investigated. Thermodynamic databases were used to predict mechanical properties—including the yield strengths—of the titanium alloy for different grain sizes, representing different post-weld heat treatment operations, and these were embedded into a finite element modelling framework to simulate the tensile testing specimens to understand the mechanical fields experienced such as stresses and strains, just prior to failure.

Tensile Strength Property with PdCo-Cu Multi-Layer Lamination and Heat Treatment of MEMS Probe for Probe Card

Cantilever wire probe card has limited to transport high-speed signal because of long wire but it is suitable for inspecting high-current and high voltage semiconductor such as wide band gap (WBG) power semiconductors.Superior mechanical property of a probe card wire is in demand because it is respectively used wafer inspection with in and out pad on the top surface of the power semiconductor wafer. Therefore, in this study, tensile specimens of micro electro-mechanical systems (MEMS) probe alternatively layered and electroplated with palladium (Pd)-cobalt (Co) alloy layers and copper (Cu) layers. MEMS probe was also measured tensile strength and elongation with multi-lamination and heat treatment conditions. Additionally, fractography of fracture surface after tensile test were analyzed using a scanning electron microscope (SEM). As the number of PdCo-Cu multi-layer increased, 11, 15 and 21 layered specimens showed higher tensile strength and longer elongation than 5 layered specimens because of the increase of laminated interface of PdCo and Cu. 7 layered specimen after isothermal aging had higher tensile strength and longer elongation than before isothermal aging. In 5, 11, 15 and 21 layered specimens, the fracture surfaces of tensile test specimens without aging treatment showed a ductile-brittle mixed fracture mode. Fracture surfaces of 7-layered specimen before and after isothermal aging showed a ductile-brittle mixed fracture mode.

Heat‐Treatment and Water Immersion Effect on the Mechanical Properties and Joint Strength of 3D‐Printed Polylactic Acid Parts

ABSTRACTThis paper investigates the effect of short‐time water immersion (WI) and heat‐treatment (HT) post‐processes on the mechanical properties and joint strength of printed polylactic acid (PLA) parts with various raster angles. Using these post‐processing methods to enhance the joint strength of printed PLA parts could be deemed as the novelty and the contribution of the current study. The WI and HT of the tensile test specimens and the adherends of the bonded joints were carried out at 21°C and 90°C, respectively. Depending on the raster angle, the tensile strength of the heat‐treated specimens was about 11%–43% higher than that of the untreated specimens. Interestingly, it was found that WI had a more significant effect on the strength of printed parts than HT. In the case of WI, the tensile strength was increased by about 27%–57% as compared to the untreated specimens. Joint tests revealed that HT and WI exerted a similar positive effect on the strength of the joints. The findings highlighted that short‐time WI is at least as effective as HT in increasing the tensile and joint strengths of 3D‐printed PLA parts.

The role of coherent nano precipitates on stacking fault and deformation twin formation during tensile deformation of wire arc additive manufactured nickel-aluminum-bronze

The strain hardening mechanisms and dislocation interactions of a wire arc additively manufactured (WAAM) nickel-aluminum-bronze (NAB) alloy was investigated using multi-scale characterization approach cross-correlating scanning electron microscopy (SEM), SEM-based electron back-scatter diffraction (EBSD), site- and crystallographic orientation-specific focused ion beam (FIB) nanofabrication, scanning transmission electron microscopy (STEM) and STEM-based energy dispersive X-ray spectroscopy (EDS). Flat, rectangular dog bone specimens were strained under uniaxial tension conditions. To understand the micro- and nanometer scale deformation mechanisms throughout the microstructure, tensile test specimens were interrupted near the yield strength and ultimate tensile strength. STEM microstructural characterization revealed that tensile deformation occurs by planar slip and multiple slip bands interacting on different {111} planes as well as the nucleation of dislocations from the interfaces associated with grains and secondary phase particles. To the authors knowledge for the first time the Center of symmetry (COS) analysis revealed that in both samples the shearing of nanoscale precipitates led to the formation of extended stacking faults including a combination of intrinsic stacking faults and 2-layer extrinsic stacking faults. At high strain levels more dislocations and stacking faults were nucleated, as well as intersecting slip bands further facilitating the activation of the stair-rod cross-slip mechanism and thickening of an ESF to create a 3-layer nano-twin. Activated mechanisms of plastic deformation and associated role of the precipitates are discussed with respect to the microscopic strength-plasticity characteristics as well as macroscopic mechanical properties of WAAM NAB alloy.

On the Competition between Pores and Hidden Entrainment Damage during In Situ Tensile Testing of Cast Aluminum Alloy Components

The competition between pores and hidden entrainment defects during tensile testing of specimens from Al-Si-Cu alloy high-pressure die castings has been characterized. In all tests, multiple strain concentrations have been identified by using the digital image correlation technique and the final fracture has been preceded by a competition between pores and hidden damage, later identified as oxide bifilms. The results have confirmed previous findings that overall damage to the metal during its liquid state is much more extensive than what can be assessed via X-ray inspection, which looks only for pores. It is concluded that current quality assurance techniques need to be updated.

Investigating the mechanical properties of composites containing exfoliated graphite/epoxy sensors: Experimental testing and simulation

One approach to structural health monitoring (SHM) involves embedding sensors within a composite material. However, the integration of these sensors can potentially introduce flaws that might affect the composite’s mechanical properties. This research aims to explore the impact of embedding exfoliated graphite (EG)/epoxy sensors on the mechanical characteristics of composite systems through laboratory experiments and numerical simulations. Sensor strips composed of varying volume fractions of EG/epoxy were fabricated. Tensile test specimens were prepared by embedding these sensors in the epoxy matrix oriented both lengthwise and widthwise. Baseline specimens of EG/epoxy without sensors were also created for comparison. Tensile tests were performed on the samples to evaluate the effects of the embedded sensors on the composite’s elastic modulus and tensile strength. The results indicated a slight improvement in both elastic modulus and tensile strength with the introduction of EG. Crucially, the orientation of the sensors within the samples had a significant impact on the composite’s mechanical properties. Samples with widthwise-aligned sensors showed reduced tensile strength due to delamination along the sensor edges. Finite element simulations using a viscoelastic model based on the experimental data were conducted to analyze the effect of sensor alignment on mechanical properties. The findings revealed that a grid pattern alignment of sensors significantly enhanced mechanical performance compared to lengthwise or widthwise alignment, particularly at 0.1% and 0.3% EG volume fractions, highlighting the effectiveness of a grid pattern for embedding sensors in SHM applications.

Influence of printing orientation on power-law hardening and ductile damage parameters for 3D-printed SS316L steel: experimental and FEA approach

In the present investigation, the selective laser melting (SLM) technique has been utilized for the 3-dimensional printing (tensile test specimens) of SS316L steel powder at 00 (horizontal) and 900 (vertical) angles. Further, an experimental and finite element analysis approach has been made to analyse the effect of printed orientation or direction on the Hollomon power law parameters (strain hardening exponent (n) and strength coefficient (K)) and ductile damage parameters (fracture strain (εf), stress triaxiality (η) and strain rate ( ε ̇ )). The influence of printing orientation on plastic deformation behavior has also been analysed. The results revealed that 00 angle 3D-printed specimens exhibited 11.05%, 21.97% and 9.50% more yield strength, tensile strength and elongation than 900 angle 3D-printed tensile test specimens. Further, the strain hardening exponent (n) and strength coefficient (K) (Hollomon power law hardening model parameters) for 00 angle 3D-printed specimens are 35.80% and 32.47% more than the 900 angle 3D-printed tensile test specimens respectively. The fracture strain for 00 angle 3D-printed specimens is 37.82% less than the 900 angle 3D-printed tensile test specimens. The percentage difference between FEA and experimental results is less than 5% which shows the good prediction capability of estimated Hollomon power law parameters and ductile damage model parameters with developed FEA model for 00 and 900 3D printed specimens.

Investigation of The Effect of CNC Milling Cutting Process on The Tensile Test of PLA Samples Produced Using Two Different 3D Printers with The FDM Method

One of the most commonly used materials in additive manufacturing with the fused deposition modeling (FDM) method is polylactic acid (PLA) filaments. In 3-dimensional (3D) printed products, an external wall is also used in addition to the internal structure pattern. The exterior wall pattern differs from the interior structure pattern. The 3D products obtained by this method contain two different pattern structures, which is not desired when determining the mechanical properties. In this study, tensile test specimens were produced with two different 3D printers using 1.75 mm and 2.85 mm diameter PLA filaments. Some tensile test specimens were directly produced in ASTM D638-14 Type 1 dimensions and subjected to tensile testing. The rest of the specimens were produced in a rectangular shape with 19 mm x 165 mm dimensions and the side edges of those specimens, produced in rectangular shape, were cut with CNC milling to bring their dimensions to ASTM D638-14 Type 1. All tensile test specimens were manufactured with a thickness of 4 mm. The test specimens cut with CNC milling after 3D printing were compared with the specimens tested only by 3D printing. The effects of CNC milling cutting on the tensile test properties of specimens produced on two different 3D printers using 1.75 mm and 2.85 mm diameter PLA filaments were investigated. Consequently, it was observed that cutting the side edges with CNC milling eliminated irregularities caused by 3D printing due to the tensile stress in those areas and allowed for more regular and consistent fractures of test specimens. When compared with only the 3D-printed specimens, the elongation at break of the tensile test specimens whose side edges were cut with CNC milling resulted in 13.45% and 33.55% higher using 1.75 mm and 2.85 mm PLA filaments, respectively. It was determined that the toughness of the samples cut by CNC milling was higher than the test samples that were only 3D printed.

Effects of Genipin Crosslinking of Porcine Perilimbal Sclera on Mechanical Properties and Intraocular Pressure.

The mechanical properties of sclera play an important role in ocular functions, protection, and disease. Modulating the sclera's properties by exogenous crosslinking offers a way to expand the tissue's range of properties for study of the possible influences on the eye's behavior and diseases such as glaucoma and myopia. The focus of this work was to evaluate the effects of genipin crosslinking targeting the porcine perilimbal sclera (PLS) since the stiffness of this tissue was previously found in a number of studies to influence the eye's intraocular pressure (IOP). The work includes experiments on tensile test specimens and whole globes. The specimen tests showed decreased strain-rate dependence and increased relaxation stress due to the cross-linker. Whole globe perfusion experiments demonstrated that eyes treated with genipin in the perilimbal region had increased IOPs compared to the control globes. Migration of the cross-linker from the target tissue to other tissues is a confounding factor in whole globe, biomechanical measurements, with crosslinking. A novel quantitative genipin assay of the trabecular meshwork (TM) was developed to exclude globes where the TM was inadvertently crosslinked. The perfusion study, therefore, suggests that elevated stiffness of the PLS can significantly increase IOP apart from effects of the TM in the porcine eye. These results demonstrate the importance of PLS biomechanics in aqueous outflow regulation and support additional investigations into the distal outflow pathways as a key source of outflow resistance.

Study the Effect of Adding Malic Anhydride and Carbon Fibers to the Mechanical and Morphology Properties of Polypropylene

Adding reinforcement materials like carbon fibers with maleic anhydride improves the strength of polypropylene. The present work aimed to study the effect of adding maleic anhydride and carbon fibers on the mechanical properties of polypropylene enhanced by presenting carbon fibers. Carbon fibers added at different ratios (0, 2, 4, 6, and 8) % and 1% of maleic anhydride were added to pure polypropylene. Standard tensile and impact test specimens were prepared per ASTM standards using an extruder technique. It was observed that increasing the carbon fiber content enhanced the tensile strength, modulus of elasticity, and hardness of polypropylene while the elongation decreased, but it enhanced after MAH addition. SEM and FTIR indicated good adhesion between fibers and polypropylene after adding maleic anhydride (MAH). UV tests showed that carbon fibers protect the composite material from the UV sunlight.

Determination of process parameters for additive manufacturing with Inconel 718 powder

Abstract In this study, the additive manufacturing (AM) of Inconel 718 was investigated, and the processing parameters can affect the mechanical properties of the product. The five-axis laser cladding composite processing machine Tongtai AMH-630 is used, and the laser power is set to 800W based on the thermal impact of the laser on the base plate. However, the laser scanning speed (600-1200mm/min) and powder feed rate (3~15g/min) are not arbitrary combinations. It is recommended to present the feed per unit length in g/mm, which seems to be more clearly expressed. Regardless of changes in laser scanning speed and wheel speed, it is a reasonable decision to control the combination of the two at about 0.01-0.013g/mm. Through single-pass cladding experiments, we select different combinations of laser scanning speed and powder feed rate with a cladding aspect ratio in the range of 3:1 to 4:1. In the multi-pass cladding experiment, an overlap rate of 30% was used as the plane cladding spacing; a spacing of 80% of the cladding height was used as the stacking height. This study uses scanning speeds of 600, 700, 800, 1000 and 1200mm/min to clad a rectangular body. Tensile test specimens were processed using a CNC lathe, and tensile tests were conducted to obtain variations in tensile strength and elongation at different scanning speeds. The mechanical properties of both will decrease as the scanning speed increases. At a scanning speed of 600mm/min, its tensile strength is comparable to that of Inconel 718 standard materials; but its elongation is 61% of that of standard materials. If Hot Isostatic Pressing (HIP) is applied after cladding, it seems that a higher scanning speed can achieve a performance closer to that of standard materials.

Membandingkan Kekuatan Pengelasan Single Dan Double Kawat Inti Elektroda (Filler Rod) Menggunakan Las Smaw

Advances in welding technology are very helpful in making, repairing or repairing chassis jobs that have a high level of difficulty and requirements. Especially in the chassis, many welding elements are involved because welded joints have an important role to support the body, engine, and vehicle load. In practical work at CV. Pringgandani Welding Analysis Comparing the Strength of Welding Results of Single Electrode Core Wire and Double Electrode Core Wire (Filler Rod) Using SMAW welding which is carried out for chassis welding which is claimed by mechanics in welding with a depth and width of more than 5 mm, it is better to use double electrode core wire which can speed up and strengthen the weld. Then a test is carried out to prove the results of the Single Wire Electrode Core and Double Electrode Core Wire (Filler Rod) welds which are stronger and faster in the process. By testing the weld results on an iron plate with dimensions of 250 mm x 50 mm x 10 mm, the welding process uses the SMAW (Shielded Metal Arc Welding) welding method. Using an E6013 type electrode with a diameter of 2 mm with a current of 90 A, polarity DCEP (Direct Current Electrode Positive) The welding position used is the 1G position or horizontal position with the welding process using a single v-groove bevel butt joint and an angle of 60o with a weld width of 10 mm and a weld depth of 8 mm. The plate samples used were two samples. In sample 1 using a single wire core electrode, and sample 2 using a double wire core electrode. All samples were made of tensile test specimens with the ASME-IX standard, a tensile test was carried out to determine and prove the respective strengths of the welding results of Single Wire Core Electrode and Double Wire Core Electrode (Filler Rod).

Failure Analysis of Cu-DHP Joining Processes: A Comparative Study of FSW and SFSW Techniques

Abstract This article presents a failure analysis conducted on specimens extracted from 2.5 mm sheets of Cu-DHP (Cu99), which were joined using friction stir welding (FSW) and submerged friction stir welding (SFSW) processes. To evaluate the performance of the welded joints, destructive and non destructive tests, including tensile tests were performed. Additionally, morphologic analysis using scanning electron microscopy (SEM) combined with energy dispersive X-ray (EDX) and fractography investigations were carried out on the samples. The results of experimental research show refined microstructures both for FSW and SFSW welding. Improved mechanical properties have been obtained for SFSW welding, compared to FSW. SFSW specimens demonstrates superior tensile strength and a higher hardness compared to FSW specimens, by performing joining process underwater. The fracture surfaces of the tensile test specimens from the base material (BM), FSW and SFSW joints, revealed the ductile fracture mechanism of the joints. EDX analysis confirms compositional integrity of the base and welded metals. Results highlights suitability of the FSW and SFSW processes for joining of copper Cu-DHP.

Experimental Determination and Simulation Validation: Johnson–Cook Model Parameters and Grinding Simulation of 06Cr18Ni11Ti Stainless Steel Welds

Hydrogen permeation resistance in the welded region of 06Cr18Ni11Ti steel is relatively weak due to surface defects, which need high integrity surface machining. The parameters of the welding material for 06Cr18Ni11Ti steel are currently unavailable, which causes some inconvenience for simulation studies. To fill the lack of 06Cr18Ni11Ti steel weld material parameters in the relevant literature at the present stage, the quasi-static tensile test at different strain rates and notch specimen tensile tests were conducted in this paper and determined the Johnson–Cook (J-C) constitutive model parameters and Johnson–Cook failure model parameters. Subsequently, a multi-grain grinding simulation model was built based on W-M fractal dimension theory by using the determined material parameters. The influence of processing parameters on grinding heat was analyzed. Grinding experiments were conducted to analyze the influence of processing parameters on grinding heat and grinding force. By comparing the simulation and experimental results, it is revealed that the average error is 9.37%, indicating relatively small discrepancy. It is demonstrated that the grinding simulation model built in this paper could efficiently simulate the grinding process, and the determined weld material parameters of 06Cr18Ni11Ti steel have been verified to possess high accuracy and reliability.

Influence of dimensional deviation and thickness non-uniformity on the small-size specimen tensile results of CLF-1 steel

Tensile testing of small-size specimens has been widely used to evaluate the influence of neutron irradiation on the mechanical properties for structural materials of fusion reactors. In recent years, researchers have been trying to standardize small-size specimen tensile test method. In the present paper, we have investigated the influence of dimensional deviation and thickness non-uniformity on the tensile results of small-size specimen by both experiments and finite element simulations, based on one of the candidate structural materials of fusion reactor, i.e. CLF-1 steel. It was found that under the conditions of small grain size, small metallurgical defect size and suitable specimen preparation, the tensile results of SS-J3 specimen could be close to the results of large-size specimen. Slightly higher yield and ultimate strengths for small specimens may be caused by the surface treatment of the wheel grinding. The repeatability of ultimate strength was better than that of yield strength, and the repeatability of elongation was worse than that of strength. For tensile tests on eight SS-J3 specimens, the maximum difference in total elongation was about 3 %. With ±0.1 mm deviation of thickness and parallel width, the maximum variation in total elongation was about 1.8 %. The ductility properties were sensitive to specimen's thickness non-uniformity, the measured uniform and total elongations would obviously decrease even with 0.01 mm thickness non-uniformity.

Microstructural behavior of CNT-PDMS thin-films for multifunctional systems

Heterogeneous ribbed and non-ribbed carbon nanotube (CNT)-PDMS thin-film systems manufactured by large-scale rolling exhibit large-strain and high strain-rate characteristics with favorable surface behaviors, such as superhydrophobicity and drag reduction. However, it is not well understood how the multi-phase microstructure and material properties of non-ribbed thin-films are related to the surface material behavior and fracture. Hence, the objective of this investigation is to characterize the large-strain mechanical behavior and the microstructure of various CNT-PDMS compositions to understand how the CNT loading, agglomeration, distribution, and orientation affect the mechanical behavior and fracture of CNT-PDMS unribbed systems. Non-ribbed thin tensile testing specimens were fabricated for neat PDMS and CNT-PDMS with different weight CNT distributions to understand non-ribbed behavior. The ultimate strain, strength, and global stress–strain behavior were obtained by uniaxial mechanical testing. Scanning electron microscopy (SEM) of the fracture surface was also obtained for each sample to analyze the microstructure and relate the damage mode to the different weight distributions. Based on these experimental measurements and observations, large-strain, hyperelastic and hyper-viscoelastic material models were used to characterize the material behavior. The hyper-viscoelastic material model was shown to provide the most accurate material description of the thin-film behavior of the viscoelastic PDMS with the high-strength CNTs.