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Based on mechanical tensile experiments on the CoCrFeNi high-entropy alloy (HEA), this study explores the forming patterns of the eccentrically shaped sub-hemispherical lined explosively formed projectile (EFP) made of the HEA material. The CoCrFeNi HEA material is initially prepared, and mechanical tensile tests are conducted at various temperatures and strain rates. The Johnson–Cook (J–C) constitutive equation for this material is derived by fitting the experimental data. Scanning electron microscopy and the energy dispersive spectrometer characterize the fracture surface of the tensile specimens, providing insights into the mechanical ductility and fracture mechanism of CoCrFeNi HEA. The EFP forming process under various charge configurations is simulated using AUTODYN software, leading to the identification of the optimal charge configuration. In addition, the damage performance is evaluated. This study provides a theoretical basis for applying HEA materials in the field of shaped charges and offers new ideas and methods for designing more efficient shaped charge warheads. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitride (h-BN) has excellent thermal conductivity and dielectric properties, which shows great potential for low-dimensional devices. However, mechanical properties of h-BN have not been comprehensively investigated through experiments. In this work, we conduct in situ direct tensile tests on freestanding single-crystal few-layer h-BN nanosheets with various layer numbers from 3 to 8, with an elaborate sample transfer and characterization protocol. Young's modulus of 573.8 ± 101.4 GPa and a tensile fracture strain up to 3.2% are revealed, which are comparable to its monolayer counterpart. Moreover, we find a tough-to-brittle transition in few-layer h-BN with the increase in layer number, which is attributed the interplay between the van der Waals interaction and in-plane covalent bonding. These findings could open up new possibilities in mechanical research of van der Waals materials and provide guidance for the design of h-BN-based devices and composites. [ABSTRACT FROM AUTHOR]

Extending the storage-recovery model, we propose a new strengthening model, premised on detailed evolution laws for both mobile and immobile dislocations, for metals under moderate to intense loading. These dislocation density evolution laws include the multiplication, storage under the effect of dislocation junctions, release of pinned dislocations, and annihilation by cross-slip. The storage-release description is derived from a simplified depiction of the probability distribution function of the dislocation length in dislocation networks. Although the model requires only few parameters to characterize the evolution of dislocation densities, remarkable agreement is found with available experimental data. From a theoretical study of the long-time behavior of the model, analytical expressions are provided to easily extract most of these parameters from experimental stress–strain curves in the quasi-static regime, whereas the parameter that governs the strength of the release process is adjusted from dynamic tensile tests. Their values so determined for polycrystalline tantalum allow the model to reproduce experimental plate-impact data with a very good match. [ABSTRACT FROM AUTHOR]

This paper proposes a numerical approach for predicting residual stresses induced during the additive manufacturing (AM) of polymer composites and their effect on the deformation behavior of the composites. A finite element (FE) model was developed on Abaqus/Standard for 3D printing of layered polymer composite using three polymers: HDPE, PVC, and ABS. The material properties of pure polymers and their blends were measured through tensile testing of injection-molded specimens. These properties were then used as input data in the FE model for the regions of pure polymers and their interfaces. An uncoupled thermo-mechanical analysis was performed, where a heat transfer analysis was realized first using elements birth (activation/deactivation) technique and a moving cylindrical volumetric heat source as a Fortran subroutine (DFLUX). With temperature input from thermal simulation, a mechanical analysis was carried out to deform the polymer composites along and across the print direction, i.e. under isostrain and isostress conditions, respectively. It was observed that the theoretical models existing in the literature underestimate the material properties as they do not consider the residual stresses developed during fabrication. The FE simulations predicted that the estimated material properties were 10 to 50% different from those calculated by the theoretical models, depending upon the residual stress level and the print direction. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study presents an in-depth investigation into the moisture absorption and mechanical behavior of Glass Fiber Reinforced Polymer (GFRP) composites and adhesive bonded joints under hydrothermal aging conditions. The aim of this research is to assess the effects of moisture exposure and aging cycles on the performance of GFRP composites and their bonded joints. The experimental program involved preparing GFRP composite specimens and adhesive samples with specific thicknesses and subjecting them to hydrothermal aging cycles. Moisture absorption and desorption behavior of the adhesive and composite specimens were evaluated using Fick's law, and equilibrium moisture content and diffusion coefficients were determined. Tensile tests were conducted to assess the mechanical properties of the materials, including elastic modulus, ultimate strength, and ultimate strain. The results demonstrated that both the adhesive and GFRP composite exhibited continuous moisture absorption and desorption behavior, following Fick's law. The moisture uptake reached a saturation point, indicating equilibrium moisture content. The diffusion coefficients of the composite were found to be significantly influenced by the saturated moisture concentrations, highlighting the role of the fiber/matrix interface. Furthermore, the mechanical properties of both the adhesive and GFRP composite were evaluated under hydrothermal aging conditions. The elastic modulus of the adhesive increased after the first aging cycle, indicating the completion of the curing process. However, subsequent cycles resulted in reduced mechanical properties due to plasticization, molecular network changes, and swelling caused by moisture. The GFRP composite exhibited a reduction in ultimate strength and elastic modulus with increasing aging cycles, along with a decrease in strain. The study revealed that the moisture absorption affected the failure modes of the bonded joints, leading to a transition from fiber failure to adhesive failure. Hybrid bonded joints, incorporating pins to distribute stress, exhibited improved stability and higher ultimate loads compared to simple joints. This work contributes to the existing body of knowledge by providing a comprehensive understanding of the moisture absorption/desorption behavior and mechanical properties of GFRP composites and adhesive bonded joints under hydrothermal aging. The findings highlight the need for further investigation into the underlying mechanisms, long-term durability, and development of moisture barrier coatings to enhance the performance of GFRP composites in challenging environmental conditions. [ABSTRACT FROM AUTHOR]

Determination of failure strains is a topic of great interest for the design of composite structures. To evaluate the ultimate strains of a composite, tensile tests have been carried out on specimens with a range of fiber orientations between 0° and 90°. Ultimate tensile strengths obtained present low or moderate dispersion, the average values constituting a good estimation of the failure stress. Values of failure strains obtained present high dispersion for almost all orientations, so it is proposed to take as failure strain threshold the minimum value for each orientation. Finally, the shear behavior of the material has been evaluated. [ABSTRACT FROM AUTHOR]

Additive manufacturing is widely used to fabricate metamaterials. The mechanical properties of these are tailored by modifying topological parameters to meet desired performance. Here, an auxetic metamaterial composed of arc-shape elements is presented. The directional dependency of the apparent stiffness was characterized through finite element analysis and tensile and compressive tests on additively manufactured samples with fused filament fabrication in thermoplastic polyurethane. Poisson's ratio was measured with computational vision. The effective Young's modulus resulted with a nonlinear relation to the wall thickness. The orientation sensibility exposed the relevance of rotational symmetry in a lattice architected metamaterial. [ABSTRACT FROM AUTHOR]

The bonding performance and formation of the interphase region between fiber and matrix have significant effects on the strength and durability of composites. A new approach, involving combined experimental and numerical analyses, has been developed to avoid the shortcomings and scattering associated with local experimental methods. For this purpose, tensile tests are performed on specimens fabricated from a single glass fiber and epoxy resin. The elongations for specified lengths are measured using the digital image correlation (DIC) technic. The size of the fiber diameter and specimen section are also measured from SEM images. The obtained experimental displacements for micro tensile tests are used in an inverse elastic finite element solution to obtain the interphase elastic modulus. It is shown that, considering the interphase thickness of 1.0 μm that is more realistic, the interphase elastic modulus is in the range of 12 ∼ 19 GPa. However, the performed sensitivity analysis shown that considering interphase thickness ranging from zero to 2.0 μm the interphase elastic modulus varies between 9 and 46 GPa. It is shown that the proposed procedure can be used to obtain the overall mechanical properties of the matrix/fiber interphase in long fiber composites. [ABSTRACT FROM AUTHOR]

The characterization of the wood behavior at the tissue scale is still scarcely explored compared with the macroscopic scale, especially for shear. This work focuses on the mechanical properties of tissue samples of Norway spruce (Picea abies). Tensile and shear tests were conducted in different anatomical directions and relative humidity (RH) levels. The results provide insights into the distinct behaviors of early- and latewood and their combination within growth rings, showing the significant impact of RH on performance. [ABSTRACT FROM AUTHOR]

To study the variation law of static tensile properties and damage mechanism of fiber metal laminates, this paper conducted static tensile tests on six types of GLARE specimens. During the testing process, the full-field strain data of the specimen were captured using Digital Image Correlation technology. A comparative analysis was conducted on the elastic modulus, tensile strength, stress-strain curve, and Poisson's ratio change curve. The fracture morphology of the specimen, strain cloud map before final fracture, and the process of strain difference formation were compared and analyzed. The results show that the bridging effect of fibers needs to be properly considered when using the hybrid model method to predict the tensile strength of the ±45°fiber-metal laminates. The role of the prepreg layer in the GLARE sample gradually increases after the metal material yields. For the same type of prepreg, the damage forms in different layers of the board are not exactly the same. Using the DIC method is helpful to study the damage process and boundary effects inside the fiber metal laminate. [ABSTRACT FROM AUTHOR]

The main aim of the present research is to improve the static tensile strength of Carbon/Kevlar/Epoxy hybrid composite by adding different nanoparticles. To this end, two well-known nanoparticles namely Nano-Silica and Nano-Graphene were considered. Also, the total percentage of adding nanoparticle reinforcing elements to the hybrid composite was considered equal to 1.5%. In this way, five categories of reinforced hybrid composites, including 0%Nano-Silica+0%Nano-Graphene, 1.5%Nano-Silica+0%Nano-Graphene, 1.2%Nano-Silica+0.3%Nano-Graphene, 1.0%Nano-Silica+0.5%Nano-Graphene, and 0.75%Nano-Silica+0.75%Nano-Graphene, were studied. Composite samples were prepared using manual layout technique and tensile tests were performed according to the ASTM standard. It was found that the tensile strength increases with the addition of nanoparticles to the Carbon/Kevlar/Epoxy hybrid composite, but these two do not always have a direct and linear relationship with each other. Moreover, it was shown that the addition of 1.2% silica nanoparticles and 0.3% nanographene leads to an increase of tensile strength up to 36%, and this is the best optimal percentage of additive nanoparticles in this research. [ABSTRACT FROM AUTHOR]

Maraging steels are used in industries that require high precision due to their exceptional mechanical properties. This paper presents the impact of ten process parameters on the mechanical properties of maraging steel produced via electron beam melting (EBM). The parameters studied here include printing orientation, scanning speed, beam power, beam diameter, line offset, layer thickness, scan strategy, number of contours, preheating temperature, and post-processing. The mechanical properties evaluated are tensile strength, strain at fracture, elongation at failure, energy density, material hardness, porosity, and surface morphology. The results showed a significant correlation between these mechanical properties and the EBM parameters. The highest ultimate tensile stress, determined from the tensile test, was recorded at 1491.51 MPa, corresponding to an energy density of 64.28 J/mm3. The optimal parameters were identified as a line offset of 0.1 mm, a layer thickness of 50 μm, a scanning speed of 2800 mm/s, and a beam power of 15 mA. The energy density during EBM in turn affected microstructure, porosity, and mechanical properties. Furthermore, the study revealed that aging heat treatment had a considerable impact on the mechanical properties, with the highest tensile strength observed for a sample that had undergone aging at 460 °C for 8 h. The results show the critical role of process parameters and aging heat treatment in achieving optimal mechanical properties in EBM-produced maraging steel M789. These findings contribute to the optimization of this manufacturing technique for industrial applications. [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]

Cold-formed thin-walled steel and fast-growing natural timber systems are highly promising composite structures. This investigation conducted tensile experiments on single-lap joints to evaluate their connection's shear properties. Three types of connections were tested: bonded, screwed, and hybrid joints. Two drilling orientations were studied within the screw and hybrid joints: timber-to-steel and steel-to-timber, to explore their discrepancy in joint performance. Numerical simulations were conducted using the cohesive zone model and nonlinear contact. The research shows a significant difference in the joints' performance with two drilling directions. The timber-to-steel screwed joint had a 29% higher average peak load capacity than the steel-to-timber screwed joint, along with 40% differences in peak displacement. Secondly, the hybrid joint exhibits comprehensive advantages over other joints. Incorporating screws improved the safety and ductility of the joint compared to the bonded joint. Moreover, the adhesive layer delays the failure of screws, resulting in a slightly enhanced second peak load compared to the peak load capacity of the screwed joints. This study demonstrates the potential performance differences of screw configuration in drilling directions. Furthermore, the mutual gain of adhesive and screws shows hybrid joints' potential benefits and suitability for engineering applications. [ABSTRACT FROM AUTHOR]

This paper extends previous studies by the authors that aimed to describe the effect of apparent cross-link density (CLD) of the rubber polymer networks on the fracture mechanism caused by cut and chip (CC) wear of natural rubber (NR), demonstrating the positive effect of conventional vulcanization (CV). This work is focused on the determination of the effect of CLD while keeping constant the accelerator-to-sulfur ratio A/S = 0.2, typical for CV systems. For this ratio, different sulfur quantities were chosen, and the concentration of the accelerator N-tert-butyl-benzothiazole sulphonamide (TBBS) was calculated to achieve CLDs in a range from 35 to 524 μmol·cm–3. Standard analyses such as tensile tests, hardness, rebound resilience and DIN abrasion were performed. From these analyses, the optimum physical properties of the NR-based rubber were estimated to be in the CLD range of approximately 60 to 160 μmol·cm–3. A CC wear analysis was performed with an Instrumented cut and chip analyzer (ICCA) and it was found that the highest CC wear resistance of the NR is in the CLD range of 35 to 100 μmol·cm–3. Furthermore, the effect of straininduced crystallization (SIC) of NR on CC wear and its dependence on the CLD region was discussed. For the first time, we determine a CLD range for a CV system in which the material achieves both optimal mechanical properties and CC wear resistance. [ABSTRACT FROM AUTHOR]

A mechanical performance of synthesizedunsatured polyester (UP) composite reinforced by OleaEuropea var. Sylvestris fibers was studied by applying the complete 23 factorial plan of experience. The variables orientation angle (V1), length (V2) and ratio (V3) of these fibers have been investigated. The experimental design was used to evaluate these factors on the Young's modulus and the maximum stress. The textural properties of the fibers were highlighted by XRD, SEM, EDS and FTIR. According to the experimental designresults, the V1 and V2 factors are the most influential and the V1V2/V2V1 and V1V3/V3V1 interactions are the most significant. The significance Student's tests of all effects were found non negligible and significant and the validation of the proposed linear models was verified by using analysis of variance (ANOVA). The study of the fracture facies of specimens of various experimental configurations by SEM showed the direct dependence of factors V1, V2 and V3 and their interactions on the improvement of the mechanical properties. Five deterioration zones were detected and identified as matrix cracking, longitudinal intra fiber cracking, fiber-matrix decohesion, fiber-matrix loosening and strong fiber-matrix cohesion. [ABSTRACT FROM AUTHOR]

This paper aims to study the impact splitting tensile properties of fly ash–recycled aggregate concrete (FARAC). The splitting tensile tests of FARAC with different replacement rates of recycled aggregate (0%, 30%, 50%, 100%) and different fly ash contents (0%, 10%, 20%, 30%) were carried out by using split Hopkinson pressure bar (SHPB) under different impact pressures (0.30 MPa, 0.35 MPa, 0.40 MPa, 0.45 MPa). The results show that the dynamic tensile strength of concrete with 30% recycled aggregate replacement rate and 10% fly ash content can be higher than that of natural concrete. It is also found that the increase of impact pressure value will enhance the dynamic tensile strength of FARAC. Eventually, the dynamic constitutive model based on ZWT constitutive model was established by considering the material damage, which can excellently forecast the dynamic stress-strain curve of FARAC and the dynamic mechanical properties. [ABSTRACT FROM AUTHOR]

This paper aims to explore the DIC technique for use in wide width tensile testing of geogrids, from specimen preparation to selection of DIC parameters required for analysis to provide a guide for a proper use. A series of monotonically loaded wide width tensile tests were conducted on a PET geogrid to investigate the effects of specimen surface preparation methods and the user-defined DIC parameters. An additional set of tests under cyclic loading was conducted to investigate the effect of the image sampling rate. The results indicate that the speckle pattern (image texture) has a significant effect on the DIC results such that the larger is the speckle size, the greater is the uncertainty level, eventually leading to increased nonuniformity in the calculated strains. Also, it was revealed that a subset size smaller than optimal, typically 20–30 pixels, results in highly localized strain distribution. A similar trend was observed in step size. In addition, the image sampling rate was found to have a significant effect on the DIC-calculated cyclic strains, such that the lower is the image sampling rate, the lower is the calculated cyclic strain. • This paper highlights important considerations for use of the DIC technique in wide width tensile testing of geogrid. • The effects of specimen surface preparation methods and the user-defined DIC parameters are investigated. • Best geogrid specimen preparation technique and optimum user-defined parameters for DIC image processing are suggested. • The importance of selecting an appropriate camera frame rate and its impact on DIC results is discussed. [ABSTRACT FROM AUTHOR]

The effect of co-existence of Mo and B on hydrogen embrittlement (HE) of equiatomic CoCrFeNi and (CoCrFeNi) 96.96 Mo 3 B 0.04 (MoB-doped) alloys are investigated through electrochemical hydrogen charging, tensile tests and advanced microstructural characterization. The MoB-doped alloy exhibits higher HE resistance than CoCrFeNi alloy, which is attributed to MoB-promoted twinning deformation process instead of conventionally strengthening grain boundary (GB) effect resulting from Mo and B segregation. As hydrogen charging time increases, the ductility of both alloys first increases and then decreases, which correlates with the competition relation between H-promoted formation of gradient twins/stacking faults and hydrogen-enhanced decohesion mechanism. For the samples charged 3 h, the beneficial effect of gradient nanostructure caused by chemical composition gradients of hydrogen overcompensates its HE effect, leading to the defeating HE of the alloys by hydrogen itself. This result indicates that the introduction of gradient nanostructures through hydrogen-concentration gradients could be a way forward for designing hydrogen-tolerant alloys. [Display omitted] • Hydrogen can enhance the ductility of CoCrFeNi and MoB-doped alloys. • Hydrogen promotes the formation of twins and stacking faults. • Segregation of Mo and B along grain boundaries are not observed. • MoB-promoted twin deformation process favors high HE-resistance of the alloy. [ABSTRACT FROM AUTHOR]

The present work aims to elucidate the effect of process parameters and pin length on microstructure and the characteristics, distribution of intermetallic compounds (IMCs), and associated failure initiation and progress pattern of AA7075 friction stir lap weld (FSLW) joints prepared employing copper interlayer. FSLW joints obtained using various combinations of tool rotation (900 and 1200 rpm), weld speeds (63 and 98 mm/min), and pin lengths (3 mm and 4 mm) are tested for tensile shear strength, fracture behavior, and the influence of IMCs formed are appraised. Further, the elastic modulus and hardness of the IMCs and neighborhood are evaluated using nanoindentation tests to correlate with the joint performance. The non-uniform thickness of AlCu, Al2Cu, and Al4Cu9 IMCs is formed due to intermixing of Al and Cu whose thickness varied with process parameters. Higher elastic modulus and hardness are recorded at the IMCs. FSLW joint prepared with 1200 rpm tool rotation, 63 mm/min weld speed, and 4 mm pin length results in better joint formation and higher strength, wherein an IMC layer thickness of around 3–4.3 µm is measured near the hook region. [ABSTRACT FROM AUTHOR]

The numerical simulation of metal cutting processes requires material data for constitutive equations, which cannot be obtained with standard material testing procedures. Instead, inverse identifications of material parameters within numerical simulation models of the cutting experiment itself are necessary. This report presents the findings from a large-scale study of dry orthogonal cutting experiments on Ti6Al4V (Grade 5) and Ck45 (AISI 1045). It includes material characterization through microstructural analysis and tensile tests. The study details the measurement of cutting insert geometries and cutting edge radii, evaluates process forces, deduces friction coefficients and coefficients for Kienzle's force model, and analyzes chip forms and thicknesses as well as built-up edge formation depending on the process parameters. The collected data, stored in pCloud, can support other researchers in the field, e.g. for recomputations within numerical models or inverse parameter identifications. The dataset includes force measurements, cutting edge scans, and chip images including longitudinal cross-sections of chips. [ABSTRACT FROM AUTHOR]

Highlights This study focused on the measurement and improvement of the radial tensile strength of composite rotors for flywheel energy storage. Filament wound carbon/epoxy composite rotors were fabricated and the radial tensile strength was measured using uniaxial tensile testing of coupons extracted from a thick rotor and diametric tensile testing of C‐rings. Compared to the uniaxial tensile test, the C‐ring test resulted in a reasonably accurate measurement of the radial tensile strength due to the absence of the effect of the curved fibers. Numerical analyses of C‐ring tests were also performed. The results matched well with the experiments and confirmed the failure of C‐rings purely because of the radial stress. The incorporation of multi‐walled carbon nanotubes in the composite rotor resulted in cohesive failure of fiber and matrix and increased the radial tensile strength by a maximum of 50%. The findings provided unique insights for accurate measurement and improvement of the radial tensile strength of composite rotors. Composite rotors were filament wound and radial tensile strength was measured. Radial tensile strength of C‐ring was accurate than that of tensile coupon. FEA of the C‐ring test validated the experimental radial tensile strength. Incorporation of MWCNT increased the radial tensile strength by 50%. Fractography showed cohesive failure indicating strong reinforcement by MWCNT. [ABSTRACT FROM AUTHOR]

Highlights This study investigates the effect of atmospheric plasma activation (APA) treatment on the thermomechanical performance of adhesively bonded skins of composite sandwich panels. The investigations show that APA treatment enhances surface wettability through the water contact angle measurements, and adhesion between the skin and honeycomb core of the panels under mechanical tests. Specifically, APA treatment results in an 11% increase in flatwise tensile strength and a 12% enhancement in the impact strength of the sandwich laminates. Flatwise tensile tests reveal superior tensile strength and toughness in APA‐treated specimens, with fracture patterns suggesting more robust adhesion. Charpy impact test results confirm increased energy absorption, reflecting better mechanical resilience. Scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA) techniques are utilized to validate these findings. Overall, APA treatment proves to be an effective technique for enhancing the performance of composite sandwich panels, offering improved adhesion, strength, and impact resistance. This approach holds significant promise for advancing high‐performance composite materials in various engineering applications. APA treatment enhances wettability and adhesion in sandwich panels. Improved adhesive distribution between skin‐core after sandwich manufacturing. 11% increase in tensile strength and 12% in impact strength with APA. Better toughness and energy absorption via SEM and DMA support in APA. [ABSTRACT FROM AUTHOR]

Highlights Electrostatic adsorption was used to self‐assemble layers of polymers and nanoparticles with varying charges onto the carbon fiber (CF) surface. This process created two distinct ionic crosslinked network layers: (3‐aminopropyl) triethoxysilane‐phytic acid‐polyethyleneimine (APTES‐PA‐PEI) and (3‐aminopropyl) triethoxysilane‐phytic acid‐nano‐silica (APTES‐PA‐SiO2). Fourier transform infrared spectrophotometer (FTIR) and X‐ray photoelectron spectroscopy (XPS) were used to confirm the presence of ionic interactions. The modified carbon fibers (CFs) exhibited increased surface roughness, higher concentration of functional groups, and improved wettability. Compared to untreated CF composites, the interfacial shear strength (IFSS) and the transverse tensile strength test (TFBT) of CF‐APTES‐PA‐PEI/epoxy composites increased by 67.8% and 62%, respectively. In contrast, the IFSS and TFBT of CF‐APTES‐PA‐SiO2/epoxy composites increased by 63.3% and 52.8%, respectively. The observed strengthening is attributed to the combined effects of ionic crosslinked networks, covalent and hydrogen bonding interactions, enhanced wettability, and the relatively roughened fiber surface. The interfacial layer design approach proposed in this study is both straightforward and effective, demonstrating significant potential for functionalizing CFs. This method is expected to be adaptable for other high‐performance fibers. The ionic cross‐linked network interface layers were designed. IFSS and TFBT were significantly improved. The enhancement mechanism was elaborated. [ABSTRACT FROM AUTHOR]

Hydrogen energy is becoming increasingly important worldwide. Due to cost-effectiveness, ferritic and martensitic steels have been commonly used for hydrogen services such as pipelines and storage tanks. However, these steels are prone to hydrogen embrittlement (HE), which causes ductility loss without affecting yield and ultimate tensile strength. Assessing hydrogen compatibility in terms of strength, especially under localized stress, which might correlate with the relative notch tensile strength (RNTS) is necessary. This study aims to establish a procedure to determine the RNTS through the small punch test (SPT) using U-shaped notch specimens in high-pressure environments at room temperature. The notch tensile strength (NTS) was calculated through simulation from the maximum equivalent stress (σ max) at corresponding fracture displacement (δ f) using the load-displacement curve obtained by SPT under each test condition. The combined experiment and numerical approach effectively determined the RNTS, confirming the SPT of notched specimens in screening the HE susceptibility of the steels. • A novel RNTS determination for hydrogen compatibility screening of ferritic steels. • A 0.2 mm depth U-shaped notch specimen as suitable geometry for NTS determination. • δ f was an effective parameter to represent the HE effect for NTS calculation. • A combined approach of SPT and simulation effectively determined the RNTS. • A strength-based HE susceptibility evaluation using notched SP specimens. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the variation in the shape memory effect in the Tan Delta output parameter of shape memory polymeric stents, fabricated by the bio-FDM process, during a reversible endothermic cycle with changes in the input parameters. Pure polycaprolactone polymer was directly used in this study. The Damping Factor, or Tan Delta, is a key factor in expressing the shape memory effect of the memory stents. For a more accurate evaluation of this effect, SEM tests, uniaxial tensile tests, and dynamic mechanical and thermal analyses were employed. The Tan Delta of the shape memory stents was approximately 18.81%. Surface morphology changes led to approximately a 14.18% variation in elastic properties, as the dynamic molecular motion and polymer chain constraints resulted in increased pressure. It was found that the fabrication input parameters led to approximately a 20% change in the shape memory effect. [ABSTRACT FROM AUTHOR]

2D polymers have emerged as a highly promising category of nanomaterials, owing to their exceptional properties. However, the understanding of their fracture behavior and failure mechanisms remains still limited, posing challenges to their durability in practical applications. This work presents an in‐depth study of the fracture kinetics of a 2D polyimine film, utilizing in situ tensile testing within a transmission electron microscope (TEM). Employing meticulously optimized transferring and patterning techniques, an elastic strain of ≈6.5% is achieved, corresponding to an elastic modulus of (8.6 ± 2.5) GPa of polycrystalline 2D polyimine thin films. In step‐by‐step fractures, multiple cracking events uncover the initiation and development of side crack near the main crack tip which toughens the 2D film. Simultaneously captured strain evolution through digital image correlation (DIC) analysis and observation on the crack edge confirm the occurrence of transgranular fracture patterns apart from intergranular fracture. A preferred cleavage orientation in transgranular fracture is attributed to the difference in directional flexibility along distinct orientations, which is substantiated by density functional‐based tight binding (DFTB) calculations. These findings construct a comprehensive understanding of intrinsic mechanical properties and fracture behavior of an imine‐linked polymer and provide insights and implications for the rational design of 2D polymers. [ABSTRACT FROM AUTHOR]

The finite‐element analysis plays a crucial role in enhancing the quality and predicting the safety of steel cord. The conventional parametric model for finite‐element analysis often overlooks the inhomogeneity of steel cord, making it difficult to achieve precise simulation. This article utilizes microcomputed tomography to track the mesoscopic deformation of real steel cord during stretching, reconstructing 3D digital images and quantitatively analyzing the corresponding rule for an optimized finite‐element modeling method. In comparison to the parametric model's experimental deviation of 28.37% in strain, the actual structural tensile model aligns with the tensile test with a deviation of only 2.88%, indicating high processing quality. In addition, when simulating the impact of layered nonuniformity on the fracture strain of cords, it is observed that a small degree of nonuniformity leads to an increase in compression between the cord filaments and subsequently enhances the fracture strain. This study provides a practical and dependable quantitative analysis on a mesoscopic scale to optimize the design and production of cords. [ABSTRACT FROM AUTHOR]

ObjectivesMethodsResultsConclusionGrain storage facility entrapments continue to be of concern in the agricultural industry, with nearly 1,500 documented incidents recorded over the last 45 years. Previous research studies have shown that attempting to extricate a full-size pulling test dummy from a grain mass requires a substantial amount of tensile or pull force – e.g. up to 1.32 kN if “buried” at waist depth, 2.77 kN at chest depth, and 4.01 kN at head depth. There is, however, a paucity of studies on the amount of distraction the human lumbar spine region can endure. The objective of this research study was to test the maximum tensile force that could be exerted on a sheep’s spine (comparable to the human spine) before the intervertebral discs and surrounding ligament would show signs of failure.Eight lumbar-region sheep spine segments were axially distracted using an MTS Criterion tensile testing machine, and the maximum forces were recorded.The average maximum force that the spinal discs and ligament withstood before showing signs of failure was 2.14 kN (standard deviation of 0.31 kN). This is comparable to the force required to extricate an individual entrapped in a grain mass at chest depth.The authors recommend that grain entrapment victims should not be forcefully pulled out if buried to waist level or above due to two primary reasons: (1) the large variation in failure load observed in our experiment with sheep spines and (2) the lack of knowledge regarding the victim’s pre-existing medical condition. The extractive forces required to remove a victim of entrapment in grain overlaps with the force needed to cause potential damage to the sheep spine, as the 1.7–3.0 kN range is comparable to the 1.65–2.48 kN force range that causes axial failure in the spine. [ABSTRACT FROM AUTHOR]

Highlights This 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. 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. [ABSTRACT FROM AUTHOR]

Among several composite repair methods, single-sided bonded patch repair is a simple and time-effective method, but its post-repair tensile strength is usually low compared to that of double-sided repair and scarf repair. Despite the tensile loading, out-of-plane bending deformation is inevitable owing to the step-like load path and generates peel stress in the adhesive layer. This study proposes a variable stiffness (VS) patch that mitigates steep stiffness changes at the edge of the patch using a curvilinear fiber orientation and verifies its effectiveness in delaying patch debonding. The damage progress in the single-sided repaired quasi-isotropic CFRP laminate under tensile loading was predicted using three-dimensional finite element analysis with cohesive elements. Although patches debonded from one end in the loading direction, the VS patch with low stiffness near the end obtained a smaller out-of-plane deformation and a higher debonding onset strain than those of the standard quasi-isotropic patch. Furthermore, tensile tests of patch-repaired CFRP specimens demonstrated an increase in the debonding onset strain by the VS patch with a small variation. These results confirmed the effectiveness of the VS patch in the single-sided bonded repair of composite structures. [ABSTRACT FROM AUTHOR]

Weak interface bonding is a critical factor that compromises the long‐term durability of the thermal barrier coatings. To mitigate this, we introduce an innovative interface‐strengthening approach by integrating four types of 3D patterns at the top coat/bond coat interface using the laser cladding technique. Tensile tests demonstrate a significant enhancement in interfacial bonding strength, increasing by over 139.2% from 21.6 ± 1.7 MPa for conventional thermal barrier coatings without patterns to 51.67 MPa for the patterned coatings. Moreover, the thermal cycling lifetime has been extended by 41%, from 1026 ± 25 cycles for the conventional coating to 1936 ± 164 cycles for the patterned coating. This enhancement in interfacial toughness and thermal cycling lifetime is primarily because of the blocking and deflection effects of 3D patterns on interfacial crack propagation. Besides, the geometric parameters of the patterns play a crucial role in determining the failure behavior of the thermal barrier coatings. This strategy presents a practical solution for the development of durable thermal barrier coatings and provides the valuable insights for the optimization of other heterogeneous interfaces. [ABSTRACT FROM AUTHOR]

The objective of this study is to improve the properties of polylactic acid (PLA), a biopolymer produced from renewable resources, without compromising its environmentally friendly "natural composite" properties. The aim was to expand the application range of PLA by making it suitable for the production of high performance composites. With this in mind, it was decided to use inorganic and environmentally friendly materials such as basalt fiber (BF) and boric acid (BA) as reinforcements. Adhesive wear and tensile tests were used to investigate the tribological and mechanical performance of the composites. Differential scanning calorimetry (DSC) and dimensional stability analysis (DSA) methods were used to investigate the thermal properties. Scanning electron microscopy analysis was also used to investigate the morphological properties of the samples. In addition, a matrix modification process using Joncryl®, an epoxy‐based chain extender chemical, was applied to enhance the interfacial interaction between the composite components and improve the composite properties by improving the dispersion of reinforcing materials. As a result of the characterization tests, it was observed that a significant improvement in the properties of the material type containing 10 wt% BF, 0.25 wt% BA and 2 wt% Joncryl® was achieved. A 19% increase in tensile strength of this type of material was observed compared with unreinforced PLA, while the sharp peak increase in the coefficient of friction (COF) curve was shifted from 20 m to 60 m. As a result, it has been presented that environmentally friendly and inorganic materials such as BF and BA can be used to produce composite materials that will serve sectors where the need and use of high performance materials is intense, especially in the automotive, aerospace and aviation sectors. Highlights: The properties of PLA matrix composites were improved by the simultaneous use of BF and BA and the addition of Joncryl®.The structural properties of PLA, an environmentally friendly polymer, have been improved without compromising this characteristic.PLA matrix natural composites with performance that can be used in the automotive, aerospace and aviation sectors have been developed. [ABSTRACT FROM AUTHOR]

The interaction properties can be significantly improved by using conjugated polymers with aromatic rings for carbon nanotube (CNT)‐reinforced composites. In this study, we investigated the influence of the molecular structure of the polyimide (PI) conjugated polymer on the mechanical properties and interfacial characteristics of CNT/PI composites. To that end, nanocomposites composed of aligned multi‐walled carbon nanotubes (MWNTs) and PI with three different molecular structures were examined. Tensile tests, small‐angle x‐ray scattering (SAXS), and molecular dynamics (MD) simulations were conducted, which revealed significant variations in the tensile properties among the three aligned MWNT/PI nanocomposites. The SAXS analyses indicated that MWNT/BPDA‐PDA had the largest interfacial specific surface area, as corroborated by the MD simulation results, which further demonstrated that the rigidity of the molecular structure influenced the extent of wrapping the PI chains around MWNTs. A highly rigid molecular chain hindered the intrachain folding of the PI chain, facilitating better wrapping of the MWNTs and a larger interfacial area. The MWNTs induced conformational changes in the PI chain owing to π–π stacking. Hermans orientation factor revealed that BPDA‐PDA exhibited the highest degree of orientation with MWNTs, whereas BTDA‐MPD displayed the greatest extent of MWNT‐induced conformational changes. The calculated interaction energy confirmed that MWNT/BTDA‐MPD exhibited the strongest interface strength (−41.50 Kcal/mol/nm2), which was 36.32% and 43.03% higher than that of MWNT/BPDA‐ODA and MWNT/BPDA‐PDA, demonstrating its superior tensile properties. This study provides insights into the interfacial characteristics between conjugated polymers and CNTs, which are essential for designing interfaces and developing high‐performance nanocomposites. Highlights: Interfacial interaction between polyimide and aligned carbon nanotubes was investigated.Modulation by polyimide structures on the mechanical property of composite was revealed.The rigidity of the polyimide hinders the folding and facilitates the wrapping.The interfacial interaction induces molecular orientation in polyimide can be observed by molecular dynamic simulation. [ABSTRACT FROM AUTHOR]

Epoxy asphalt, a thermosetting polymer, is characterized by stable, irreversible internal chemical bonds that prevent recovery and spontaneous micro‐crack healing, unlike conventional asphalt. This study introduces a renewable nano‐modifier synthesized via esterification of carboxyl‐functionalized carbon nanotubes (CNTs‐COOH) and furfuryl alcohol (FA), termed CNTs‐FA. The successful synthesis of CNTs‐FA was confirmed through various microscopic techniques. Integrating CNTs‐FA into epoxy asphalt materials, the optimal dosage was identified as 0.05% of the total epoxy asphalt mass using tensile tests and fluorescence microscopy. Thermal reversible effects and mechanisms were further analyzed through multiple regeneration cycles using tensile properties, fluorescence microscopy, and infrared spectroscopy. The study elucidates that the thermal reversibility in epoxy asphalt is facilitated by the Diels‐Alder (DA) reaction between the conjugated diene structure in FA and the curing agent oleylamine. This research provides an effective solution to the non‐recoverability and unrepairable micro‐cracks of traditional epoxy asphalt mixtures. Highlights: CNTs‐FA was successfully prepared by esterification reaction.Using nano modification methods, introduce DA reaction into curing system.Renewable function of epoxy asphalt by DA reversible reaction. [ABSTRACT FROM AUTHOR]

Fiber‐reinforced polymers (FRP) feature high strength‐to‐weight ratio amongst the emerging class of natural composites. This paper presents the impact of the glass fiber on the tensile strength of the flax epoxy laminate. The mechanical behavior and damping characteristics of flax fiber reinforced polymer (FFRP) and the hybrid flax‐glass fiber reinforced polymer (HFRP) are experimentally investigated. Both the flax and hybrid FRPs are made using vacuum infusion process. The specimens without and with holes of 4, 5, and 6 mm in diameter are subjected to tensile test using acoustic emission monitoring and free vibration test. In the former testing, HFRP resulted in higher peak frequencies and cumulative counts. Also, the natural frequency and damping factor of HFRP vary proportionately with the hole size, as identified in the latter tests. Different damage mechanisms during the tensile test revealed that the presence of glass fibers in HFRP increased resistance for certain damage mechanisms. Highlights: Adding glass fiber to flax fiber reinforced polymer (FFRP) creates a hybrid FRP (HFRP) with increased resistance to damage and improved damping characteristics.HFRP exhibits a distinction in failure mechanisms compared to FFRP.The study utilizes acoustic emission (AE) to identify various damage mechanisms in the material, providing a more detailed information.The addition of glass fibers in HFRP leads to a more pronounced increase in damping factors. [ABSTRACT FROM AUTHOR]

AbstractThis study explores the formability of laser-welded tailored blanks in the context of single-point incremental forming (SPIF), a flexible and dieless manufacturing process. Two approaches, variation in materials and thicknesses, were used to fabricate tailor-welded blanks (TWB) with CRCA and DD steel sheets. The quality of the weld was evaluated by metallographic studies and tensile tests. The ductility of the welded joint was reduced by 81%, and the hardness was increased by 133% compared to the base metal. SPIF was employed using a hemispherical tool to form a ‘D’ shape geometry on fabricated TWBs. Fracture was observed only at the weld line, irrespective of thickness and material combination in the TWB. The forming height achieved from the SPIF of TWBs was reduced by 24% and 34% for both differences in thickness and material when compared to their corresponding base metals. Finite Element simulations were performed in Abaqus software using a dynamic explicit approach employing von Mises and Hill48 yield functions. Further, the FE model was validated by comparing the thickness and surface major/minor strains at the same forming height as observed from the experiments. Reduced formability and no weld line movement were the main observations made in this study, and the same was manifested by the FE simulation. [ABSTRACT FROM AUTHOR]

Organic photodetectors (OPDs) hold immense promise for stretchable and wearable applications, but their photoactive films demonstrate brittleness, stiffness, and mechanical instability, posing challenges for future applications. Herein, the nanoconfinement effect is reported to substantially improve the stretchability and mechanical stability while reducing the stiffness of photoactive films, simultaneously maintaining the high light detection performance. The microstructure, mechanical properties, and photoelectric performance of the quaternary blend films with varying elastomer contents are thoroughly characterized. Additionally, the elastic modulus of quaternary blends can be accurately predicted by the Coran–Patel model. Cyclic tensile tests demonstrate enhanced mechanical stability, resulting in a specific detectivity of the quaternary blend with the nanoconfinement effect being 19 times higher than that of the ternary blend after 200 cycles. Overall, this study provides novel insights into constructing stretchable blend films for wearable electronics. [ABSTRACT FROM AUTHOR]

To investigate the influence of special nanopore shapes on the mechanical properties of graphene at the atomic scale, a suitable nonlinear atomic-scale finite element model (AFEM) is developed based on the Stillinger Weber interatomic potential (SW). The discrete element created is an atomic finite element consisting of ten atoms, which can capture the dominant local and non-local atomistic interactions dictated by the present interatomic potential. Furthermore, the anterior works demonstrated the simplicity and the accuracy of the SW potential compared to the well-known interatomic potentials used in AFEM for predicting the elastic and fracture properties of graphene. The accuracy of the present model is checked by studying the graphene mechanical properties under the tensile and the shear tests, the comparison between our results and those reported in the literature showed a better agreement. The effect of diamond, hexagonal and rectangular nanopores, as well as their orientations on the elastic and fracture properties of graphene under the tensile and shear tests is also studied. Notably, previous literature lacks a comprehensive study on the shear properties of graphene under nanopore shapes. Our results show that the graphene's mechanical properties are more affected by the nanopores oriented perpendicular to the direction of the applied load. Particularly, the nanopores with elongated sharp tip edges, such as the diamond shape, have the greatest impact on graphene's mechanical response. The results show the ability of the present AFEM to investigate the mechanical behavior of graphene in the presence of various nanopore shapes with high precision at reduced computational time compared to its counterparts. Additionally, it offers simplicity and efficiency in studying large-scale systems. [ABSTRACT FROM AUTHOR]

Polyolefin elastomers are typically copolymers of ethylene with 1-butene, 1-hexene, or 1-octene. Other types of comonomers have not been widely applied industrially. The cost of 1-heptene obtained from Fischer-Tropsch synthesis is only half that of 1-octene, making it a viable economical substitute. This work utilized 1-heptene from Fischer-Tropsch synthesis and 1-octene from ethylene oligomerization as research subjects. Eight metallocene POEs based on 1-heptene and 1-octene were synthesized using Me2Si(C5Me4)(NtBu)]TiCl2 (Ti-CGC) catalyst. The copolymers' molecular structures and physical properties were characterized using HT-GPC, Temperature Rising Elution Fractionation (TREF),13C-NMR, DSC, Melt Index (MI), and Tensile tests. Compared to 1-heptene, 1-octene more effectively reduces the melting point and crystallinity, while 1-heptene's stronger comonomer insertion capability facilitates the production of copolymers with higher comonomer content. Similar ternary sequence distributions and molecular dynamics indicate that ethylene/1-heptene and ethylene/1-octene copolymers possess comparable chain microstructures. Both ethylene/1-heptene copolymers and ethylene/1-octene copolymers exhibit excellent toughness and mechanical properties. Although the activity and insertion capacity of ethylene and 1-heptene decrease at low comonomer concentrations, they significantly improve at higher comonomer concentrations. Thus, Fischer-Tropsch synthesis of metallocene ethylene/1-heptene copolymers can effectively reduce raw material costs and be a cost-effective alternative to ethylene/1-octene copolymers. [ABSTRACT FROM AUTHOR]

Background/Objectives: The Achilles tendon is a popular allograft option for anterior cruciate ligament (ACL) reconstruction. Structurally, the tendon is known to have a 90-degree rotational fiber track. Preparation techniques, with this consideration, may influence the strength of the graft. This study aims to assess the tensile strength of a novel Achilles tendon allograft harvest procedure following the rotational fiber track. Methods: Both Achilles tendons were harvested from formalin-embalmed cadavers [(n = 20), male n = 13, female n = 7, average age = 70]. Ten cadavers had the right Achilles as the control and the left Achilles as the fiber track sample; 10 cadavers had the opposing designation. Tensile strength was tested utilizing a Bose machine. An unpaired t-test was used to compare data across groups. Results: The average ultimate load for the control group was 874.17 N, with an average elastic stiffness of 76.01 N/mm. The ultimate load for the fiber track group was 807.84 N, with an average elastic stiffness of 64.75 N/mm. No statistically significant difference (p = 0.21) was determined between the average ultimate loads or elastic loads (p = 0.18) across groups. Conclusions: These data suggest that the rotational fiber track method of Achilles allograft has consistent tensile strength and elastic stiffness as compared to the common harvest procedure. The rotational fiber track method for ACL harvesting is a viable alternative option to the common harvest procedure for usage in an ACL reconstruction. [ABSTRACT FROM AUTHOR]

This article delivers a new Preisach model representing the correlation between the elastoplastic behavior of structural mild steel under axial monotonic and cyclic loading with damage. The newly formed model is based on the experimentally defined correlation between axial monotonic and cyclic behavior of structural mild steel. To examine the monotonic and cyclic behavior of structural mild steel and find fitting material properties for the model, monotonic and cyclic axial tensile tests are performed. Tests are executed on coupons of the commonly used European structural steel S275. The model represents a mathematical description of modified single-crystal material behavior under monotonic loading. Two different approaches were used to describe damage in the multilinear mechanical model. The excellent agreement with experimental results is achieved by infinitely linking many single-crystal elements in parallel, forming the polycrystalline model. This model provides a good solution for everyday engineering practice due to its geometric representation in the form of the Preisach triangle and the lower costs of monotonic tests used to define material properties compared to cyclic tests. [ABSTRACT FROM AUTHOR]

This study explores a novel approach to obtaining 3D printed strain sensors, focusing on how changing the printing conditions can produce a different piezoresistive response. Acrylonitrile butadiene styrene (ABS) filled with different weight concentrations of carbon nanotubes (CNTs) was printed in the form of dog bones via fused filament fabrication (FFF) using two different raster angles (0–90°). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) in TUNA mode (TUNA-AFM) were used to study the morphological features and the electrical properties of the 3D printed samples. Tensile tests revealed that sensitivity, measured by the gauge factor (G.F.), decreased with increasing filler content for both raster angles. Notably, the 90° orientation consistently showed higher sensitivity than the 0° orientation for the same filler concentration. Creep and fatigue tests identified permanent damage through residual electrical resistance values. Additionally, a cross-shaped sensor was designed to measure two-dimensional deformations simultaneously, which is applicable in the robotic field. This sensor can monitor small and large deformations in perpendicular directions by tracking electrical resistance variations in its arms, significantly expanding its measuring range. [ABSTRACT FROM AUTHOR]

In the present study, biocomposite materials were created by incorporating biochar (BC) at rates of 1, 2.5, and 5 wt.% into a poly(butylene succinate) (PBSu) matrix using a two-stage melt polycondensation procedure in order to provide understanding of the aging process. The biocomposites in film form were exposed to UV irradiation for 7, 14, and 21 days. Photostability was examined by several methods, such as Fourier transform infrared spectroscopy (FTIR), which proved that new carbonyl and hydroxyl groups were formed during UV exposure. Moreover, Differential Scanning Calorimetry (DSC) measurements were employed to record the apparent UV effect in their crystalline morphology and thermal transitions. According to the molecular weight measurements of composites, it was apparent that by increasing the biochar content, the molecular weight decreased at a slower rate. Tensile strength tests were performed to evaluate the deterioration of their mechanical properties during UV exposure, while Scanning Electron Microscopy (SEM) images illustrated the notable surface alternations. Cracks were formed at higher UV exposure times, to a lesser extent in PBSu/BC composites than in neat PBSu. Furthermore, the mechanism of the thermal degradation of neat PBSu and its biocomposites prior to and upon UV exposure was studied by Pyrolysis–Gas Chromatography/Mass Spectrometry (Py–GC/MS). From all the obtained results it was proved that biochar can be considered as an efficient UV-protective additive to PBSu, capable of mitigating photodegradation. [ABSTRACT FROM AUTHOR]

In this study, olive pit agro-waste from the olive oil industry is valorized by incorporating it as an additive in a polyethylene terephthalate glycol (PETG) matrix to develop bio-based composite materials for large format additive manufacturing (LFAM). The olive pits were first ground into olive pit powder (OPP) and then functionalized by polymerizing poly(butylene adipate-co-terephthalate) PBAT on their surface, resulting in a hydrophobic, modified olive pit powder (MOPP) with enhanced compatibility with the PETG matrix. OPP and MOPP composites were compounded and 3D-printed via Fused Granular Fabrication (FGF) using 5, 10, and 15 wt.% concentrations. The PBAT coating increased the degradation temperature and specific heat capacity of the material, contributing to a lower melt viscosity during printing, as confirmed by MFR, MDSC, and TGA analyses. Tensile testing revealed that MOPP composites generally exhibited superior mechanical properties compared to OPP composites, likely due to the improved compatibility between PBAT on the MOPP surface and the PETG matrix. SEM analysis further validated these findings, showing a highly irregular and porous fracture surface in OPP composites, while MOPP composites displayed a smooth surface with well-integrated MOPP in the PETG matrix. [ABSTRACT FROM AUTHOR]

Material selection is the main challenge in the drone industry. In this study, hardness, abrasive wear, impact resistance, tensile strength, and durability (frost resistance and accelerated ageing) were identified as important characteristics of drone materials. The additive manufacturing technology was used to produce the drone leg specimens and prototype. The suitability of PETG as a primary filament material in the design of the drone leg was investigated. Nine series were printed with different raster lines (0.1, 0.2 and 0.3 mm) and infill densities (30, 60 and 90%). Printed specimens were annealed in salt and alabaster, as well as immersed in liquid nitrogen. Series with raster line-infill densities of 0.1–30, 0.3–30, 0.1–90 and 0.3–90 were identified as the most interesting ones. Thermally treated specimens had better mechanical and durability properties, and infill density was found to be the most important printing parameter. Specimen annealed in salt with a raster line of 0.1 mm and infill density of 90% had the best results. Since ABS is the most common material used for drone leg production, its properties were compared with the PETG specimen, which showed the best properties. The potential of PETG as an alternative material was proven, while the flexibility, productivity and suitability of the leg drone design were additionally confirmed. [ABSTRACT FROM AUTHOR]

Methyl gallate (MG) and gallic acid (GA) are natural compounds with potent activity against methicillin-resistant Staphylococcus aureus (MRSA), a significant global health concern. In this study, MG and GA were incorporated into cellulose acetate (CA) blended with poly(vinyl alcohol) (PVA) to create electrospun nanofibers aimed at combating both methicillin-susceptible S. aureus (MSSA) and MRSA. Key electrospinning parameters—DC voltage, injection flow rate, and syringe tip–collector distance—were optimized, with the best conditions being a 1.5 mL/h flow rate, 30 cm distance, and 20 kV voltage. The resulting nanofiber mats were characterized by SEM, FTIR, DSC, tensile strength testing, contact angle measurement, swelling behavior, and release profiling. Antibacterial properties were assessed using the agar diffusion test. The obtained nanofibers had diameters ranging from 879.33 to 906.13 nm. Among the samples, MG-GA-CA/PVA exhibited the highest tensile strength, good flexibility, and improved stiffness, which was related to enhanced thermal stability and chemical interactions as shown by DSC and FTIR analyses. This formulation also displayed excellent hydrophilicity, swelling properties, and a consistent release profile over 8 to 24 h. Furthermore, MG-GA-CA/PVA showed superior antibacterial activity against both MSSA and MRSA, suggesting its potential as a strong, flexible, and effective anti-S. aureus material. [ABSTRACT FROM AUTHOR]

A model based on the fitting of stress–strain data by tensile tests of bio-composites made of a bioplastic (polybutylene succinate (PBS)) and brewer spent grain filler (BSGF) is developed. Experimental tests were performed for various concentrations of BSGF in the range from 2% to 30%. The model is suitable for describing the elastic–plastic behavior of these materials in terms of two mechanical parameters, tensile stress and tensile stiffness (or Young's modulus), depending on the filler concentration. The mechanical characteristics, derived from the fit parameters, show good agreement with the experimental data. The mathematical model used here could be an important aid for the experimentation and manufacturing process as it allows the prediction of the mechanical tensile parameters of a mixture with different filler concentrations, avoiding the long and complex preparation cycle of bio-composites, as well as the specific mechanical tests. The physical properties required by the objects created with the PBS–BSGF bio-composite by the partners/stakeholders of the research project co-financing this research can be quite different; therefore, a mathematical model that predicts some of the mechanical properties in terms of the mixture composition may be useful to speed up the selection of the required amount of BSGF in the mixture. [ABSTRACT FROM AUTHOR]

The development of thermoplastic starch (TPS) films is crucial for fabricating sustainable and compostable plastics with desirable mechanical properties. However, traditional design of experiments (DOE) methods used in TPS development are often inefficient. They require extensive time and resources while frequently failing to identify optimal material formulations. As an alternative, adaptive experimental design methods based on Bayesian optimization (BO) principles have been recently proposed to streamline material development by iteratively refining experiments based on prior results. However, most implementations are not suited to manage the heteroscedastic noise inherently present in physical experiments. This work introduces a heteroscedastic Gaussian process (HGP) model within the BO framework to account for varying levels of uncertainty in the data, improve the accuracy of the predictions, and increase the overall experimental efficiency. The aim is to find the optimal TPS film composition that maximizes its elongation at break and tensile strength. To demonstrate the effectiveness of this approach, TPS films were prepared by mixing potato starch, distilled water, glycerol as a plasticizer, and acetic acid as a catalyst. After gelation, the mixture was degassed via centrifugation and molded into films, which were dried at room temperature. Tensile tests were conducted according to ASTM D638 standards. After five iterations and 30 experiments, the films containing 4.5 wt% plasticizer and 2.0 wt% starch exhibited the highest elongation at break (M = 96.7%, SD = 5.6%), while the films with 0.5 wt% plasticizer and 7.0 wt% starch demonstrated the highest tensile strength (M = 2.77 MPa, SD = 1.54 MPa). These results demonstrate the potential of the HGP model within a BO framework to improve material development efficiency and performance in TPS film and other potential material formulations. [ABSTRACT FROM AUTHOR]