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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]

Purpose: To evaluate the effect of adding tea tree oil to denture liners on Candida albicans and bond strength to the acrylic denture base. Materials and Methods: Disc-shaped specimens were fabricated from silicone-based resilient liner (Tokuyama, Molloplast), acrylic-based hard liner (GC Reline), and acrylic-based soft liner (Visco-gel). Tea tree oil (TTO) was incorporated into the liners at varying concentrations (0% [control], 2%, 5%, 8%). C albicans were counted by viable colony count, and optical density (OD) was measured with a spectrophotometer. The tensile strength to heat polymerized acrylic denture base was measured in a universal testing machine. The compliance of the data to the distribution of normality was evaluated using the Shapiro Wilk test. Two-way ANOVA, Bonferroni correction, and paired sample t test were performed (α = .05). Results: The addition of TTO into liners provided a significant decrease in the OD values (P < .001). The control groups of the liners presented the highest colony counts, whereas increasing TTO decreased the results (P < .01). According to tensile bond strength test, 8% TTO addition resulted in a significant decrease for Tokuyama (P < .01) and Molloplast liners (P < .05), while 2% TTO resulted in significance for GC Reline (P < .001). Conclusions: Denture liners containing increasing percentages of TTO presented lower amounts of C albicans colonies and decreased bond strength to the denture bases. When using TTO for its antifungal properties, the amount added should be carefully selected because the tensile bond strength may be affected. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the influence of contamination and different cleaning methods on resin bonding to cobalt-chromium (CoCr) alloy disks. Materials and Methods: A total of 160 CoCr disks were divided into 3 groups. The first group (N = 64) was air abraded with alumina particles; the second group (N=64) was air abraded and contaminated with silicone disclosing agent and saliva; the third group (N=32) was neither air abraded nor contaminated. The first two groups were divided into 4 subgroups (N = 16) according to the cleaning method: ultrasonic bath in 99% isopropanol, use of a cleaning suspension of zirconium oxide particles, use of a cleaning suspension based on 10-MDP salt, and treatment with atmospheric plasma. The third group was divided into 2 subgroups (N = 16): treatment with atmospheric plasma and no treatment. All CoCr specimens were bonded to plexiglas tubes filled with a bonding resin that contained phosphate monomer. Tensile bond strength (TBS) was examined by tensile testing after 3 and 150days of water storage plus 37,500 thermal cycles (N = 8). Results: After contamination, TBS was significantly reduced after 150days of water storage. Groups without air abrasion showed initially low TBS and debonded spontaneously after 150days of water storage. Conclusion: None of the cleaning methods was able to remove saliva and silicone disclosing agent on CoCr-alloy surfaces. Surface activation by plasma treatment has no long-term effect on the bond strength. [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]

Incorporating graphene oxide (GO) with controlled localization into poly(butylene adipate‐co‐terephthalate) (PBAT) blends with poly(ethylene vinyl alcohol) (EVOH) aimed to improve barrier properties, biodegradability, and mechanical strength of PBAT. The PBAT/EVOH/GO nanocomposites containing 0 to 1 wt% of GO were prepared by a reactive mixing process in internal mixer. Microscopic images confirmed that the GO nanoplatelets are mainly localized in PBAT phase and then at the interface, contrary to the thermodynamic affinity of GO toward EVOH. The reactive nature of PBAT/EVOH/GO nanocomposites was confirmed via time‐sweep rheological studies where specific changes were observed in melt viscosity over time. The results of microscopic studies, rheometry, tensile test, and dynamic mechanical thermal analysis (DMTA) confirmed that localizing GO at the interface establishes strong interactions between PBAT and EVOH. By the addition of 0.75 wt% GO, tensile and yield strength were improved by 19% and 45%, respectively. Increasing GO significantly increased the hydrolysis degradation rate of the nanocomposites. Furthermore, the addition of GO considerably decreased the oxygen and water vapor permeability of the blends by up to 40% at 1 wt% GO. [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 scientific community has become interested in cellulose extraction from agro-industrial wastes because they contain large quantities of cellulose and are being researched globally due to their application. Cellulose extracted from these wastes offers varying characteristics and structures depending on the specific source. In this study, microcrystalline cellulose (MCC) was extracted from different parts of the durian husk through acid hydrolysis with various concentrations of oxalic acid and cellulose-to-acid ratios. The durian husk underwent a pretreatment method involving bleaching and alkaline treatment. The characteristics of MCC, such as functional group, morphology, and crystallinity, were studied. The findings indicated that lignin was successfully removed through pretreatment. However, traces of hemicellulose were still detected in a few samples. The extracted MCCs demonstrated a diameter range from 6.237 to 25.38 μm and crystallinity within the range of 71.43–78.30%. Polycaprolactone (PCL)-based biocomposites with different MCC weights (0.2, 0.5, and 1.0 wt%) were fabricated, and the performance was evaluated through tensile testing and biodegradability tests. The addition of 1.0 wt% MCC enhanced the tensile strength by 22%. SEM analysis revealed the cross-section fracture surface of the biocomposite, indicating the contribution of the MCC during pull-out. Meanwhile, the biodegradability of the biocomposite increased with the addition of MCC, indicating that the MCC-based biocomposite was fully biodegradable. [ABSTRACT FROM AUTHOR]

This study investigates the role of pin profile in the interfacial characterization of friction stir welded (FSWed) T-lap joints fabricated with dissimilar aluminum alloys (AA5083 and AA7075) under regimes of two welding passes. Various pin offset distances and three pin profiles (cylindrical non-threaded, cylindrical threaded, and triangular pins) were examined with the results indicating that the pin profile significantly affected the interfacial morphology and formation of kissing bonds (KBs). Threaded pin produced a higher and wider mixing zone but resulted in larger KBs. The cylindrical non-threaded and triangular pins minimized the size of KBs but exhibited weaker material mixing. The pin offset had minimal effect on the interface morphology but reduced the size of KBs remarkably with increasing distance offset. The mechanical performance of the T-lap joints was evaluated through tensile tests, hardness distribution, and local strain using digital image correlation analysis. Increasing the pin offset improved joint strength, particularly in the stringer test. The cylindrical non-threaded pin achieved the highest joint efficiency (90 pct compared to the base material) owing to its optimal balance between effective bonding width and effective skin thickness. KBs were identified as the weakest point in the FSWed T-lap joint, causing localized strain and influencing the fracture behavior. [ABSTRACT FROM AUTHOR]

Titanium matrix composites (TMCs) have application prospects in the aerospace, military, and automobile sectors. In this paper, novel hybrid-reinforced TMCs with both high strength and ductility were fabricated by introducing tungsten particles (WP) and in-situ synthesized ceramics (TiBW + TiCP) as combined reinforcements. Systematic multiscale microscopic analyses, thermodynamic calculations, and quasi-static tensile tests revealed the microstructures and synthesis mechanism of hybrid reinforcement clusters and their strengthening effect on the Ti-alloy matrix. In the TMCs, the hybrid reinforcements had a core-shell structure with WP as the core and ceramic phases as the outer layer. The ceramic shell contains various phases such as TiC, TiB, W2C, and WC formed by an in-situ synthesis reaction between B4C, W, and Ti during sintering. The TMC with 3.2 vol pct hybrid reinforcements demonstrated the best mechanical properties with a yield strength of 896.39 MPa, ultimate tensile strength of 1081.23 MPa, and fracture strain of 11.1 pct. As the WP content increased, the mechanical properties of the TMCs gradually deteriorated due to reinforcement agglomeration. The higher strength of TMCs was attributed to various strengthening mechanisms. When the WP content increased, the strength increase caused by grain refinement was weakened, but the contributions of dislocation multiplication and load transfer were enhanced because the reinforcement clusters were larger and more continuous. The "filling" behavior of WP eliminated micropores caused by the Kirkendall effect during the in-situ reaction between B4C and Ti, which improved the density and ductility of hybrid-reinforced TMCs. [ABSTRACT FROM AUTHOR]

This paper presents the development of the photocurable resin material based on the graphene reinforced polyethylene glycol diacrylate (gPEGDA) for vascular stent fabrication using a commercial 3D printer. 3D printing with digital light processing (DLP) technique is an attractive alternative for low-cost fast fabrication with high accuracy. Four photocurable resin compositions were prepared by mixing PEGDA and varied composition of graphene and the photoinitiator according to the design of experiment of 22 full factorial design. The diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO) photoinitiator was adopted to meet the required 405 nm UV-light source wavelength of the 3D printer for stent fabrication. Material characterization of the UV-absorbance and viscosity tests were conducted and optimized to obtain resin printability. Mechanical characteristics tests were conducted to obtain the best resin composition for stent application. For this purpose, the tensile tests were conducted according to the ASTM D638 standard using the type-V specimen size. The test specimens were 3D printed with varied UV exposure time 20 and 30 seconds. Finally, the stents were successfully fabricated using a commercial 3D printer DLP with the bottom parameter time setting of 60 seconds, and the UV exposure time of 30 seconds. The resin material was applicable for 3D printing of the stent. The result has shown that 3D printer with DLP technique is suitable for stent fabrication with excellent surface quality. Moreover, the innovative bioresorbable stent materials and fabrication approach could open up new possibilities in the development of medical devices, particularly in the treatment of vascular diseases. [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]

This study evaluated the influence of adding borosilicate residue (BS) as a flame retardant in polypropylene (PP) and natural fiber composites. The natural fibers used in this study come from the residue of the carpet industry, which is composed of PP and jute fibers (JT), while the PP used as the polymer matrix is postindustrial recycled material. The composites were produced by corotational twin‐screw extrusion and injection molding to obtain the test specimens. A coating process was carried out to add the water‐soluble fraction of BS to the surface of the compositions that did not receive it through incorporation during processing. To characterize the composites, flammability tests, thermogravimetric analysis (TGA), tensile strength test, and morphological analysis by scanning electron microscope (SEM) were performed. The addition of only 2 wt% BS content induces an increase in thermal stability of 32 and 109°C for composites with and without natural fibers, respectively. The addiction of 20 wt% BS elevates the elastic modulus up to 27% of the composites with and without natural fibers. The BS characterization indicates that it could be applied as a flame retardant when applied as coating methods using the water‐soluble fraction of BS, reducing the burning rate up to 92%. Flammability results are similar for formulations with and without natural fibers, indicating that the natural fibers did not influence the proposed flame retardant. The findings suggest that BS coating is a potential solution to improve the properties of natural fiber‐reinforced polymer composites while also promoting waste recycling. This approach produces composites with improved flammability, thermal stability, and mechanical properties, making them suitable for various end applications. [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]

In this study, we delved into innovative strategies to make neat E‐glass fabrics (NGFs) more impact‐ and tensile‐resistant by using shear‐thickening fluids (STFs). To achieve this goal, the polyethylene glycol (PEG) in STFs has been modified. Subsequently, the STF‐impregnated fabric composites were prepared from unmodified PEG and functionally modified PEGs using malonic and tartaric acids, V/S/GF, M/S/GF, and T/S/GF composites, respectively. Fourier‐transform infrared spectroscopy (FTIR) analysis was conducted to confirm the chemical modification of PEGs. The rheological tests showed a significant improvement in the peak viscosity of modified STFs compared with virgin STF. Dynamic rheological analysis also studied media‐particle interaction, revealing improved media‐particle interaction in STFs due to abundant H‐bonding. In addition, a series of experimental tests, namely compressive impact resistance and strip tensile strength tests, have been conducted to investigate the effect of STF modification on the NGF. The results revealed notable improvements in tensile strength and energy dissipation in the T/S/GF and M/S/GF composites compared with V/S/GF and NGF. Importantly, this improvement extended to the impact performance of single, triple, and quintuple layers. Notably, we found that the peak load of 5 T/S/GF was 37.71%, 18.57%, and 11.87% lower than that of 5NGF, 5 V/S/GF, and 5 M/S/GF, respectively. The idea that made these improvements possible came from PEG functionalization, which helps hydrogen bonds form between the dispersed phase and the dispersion medium, leading to higher viscosity. This, in turn, increases inter‐yarn friction, effectively enhancing the spring‐like properties of T/S/GF and M/S/GF compared with V/S/GF. A two‐step artificial intelligence regression analysis underpinned these findings, elucidating the interplay of molecular mechanisms in high‐performance fabric composites. [ABSTRACT FROM AUTHOR]

Poly(N‐vinylcaprolactam) (PNVCL) is a thermoresponsive polymer, which presents a transition from hydrophilic to hydrophobic behavior close to the physiological temperature, being promising for biomedical applications. However, the production of finished products with PNVCL is difficult due to its high mechanical fragility in the solid state. In the present work, in order to prepare a thermoresponsive film with good mechanical properties, a blend of PNVCL with thermoplastic polyurethane (TPU) was prepared. Three compositions of PNVCL/TPU were studied with mass proportions of 90/10, 70/30, and 50/50, respectively. The films were flexible, miscible and presented different thermoresponsive behaviors, with changing from transparent to opaque varying from 31 to 40°C. Contact angle analysis showed significant changes in the hydrophilicity of the films' surfaces with temperature variation. Moreover, it was possible to induce a change in solid films from transparent to opaque by varying the temperature and verify the reversibility of this change. In addition, tensile tests were carried out, which proved, for PNVCL/TPU blends, the reduction of film brittleness with TPU increase. To the best of our knowledge, it is the first work that presents thermoresponsive properties of solid films formed by a blend of PNVCL and TPU. [ABSTRACT FROM AUTHOR]

The mechanical performance degradation of welded seams under cyclic loading may lead to the failure of membrane structures. To investigate the influence of the off-axis angle and the the welded width on mechanical performance, the elastic modulus, ratcheting strain, residual strain and strain energy were studied based on the uniaxial cyclic tensile tests of welded seams. The results show that the elastic modulus of the welded seam specimens shows obvious anisotropy under cyclic loading, and the welded width has the greatest influence on the elastic modulus of the welded seam specimens with 15° and 75° off-axis angles, under which off-axis angle the welded seam specimens have good recoverability. The irreversible plastic strain of the axial welded seam specimens is close to that of the membrane specimen. The plastic development of the specimen is obvious under large off-axis angles (30°, 45°, 60°), and the final residual displacement of the welded seam specimens reach 3%–4%. [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]

Six varieties of alkoxy polyhedral oligomeric silsesquioxanes (POSSs) featuring methoxy, ethoxy, n‐propoxy, isopropoxy, n‐butoxy, and n‐hexoxy as terminal groups were synthesized using the direct dehydrogenation condensation method. These POSSs were then incorporated as cross‐linking agents into hydroxy‐terminated polydimethylsiloxane (HPDMS) to create various formulations of room temperature vulcanized silicone rubbers (RTV SRs), denoted as SRM, SRE, SRP, SRI, SRB, and SRH. The morphology, thermal stability, and mechanical properties of the resulting SRs are analyzed using scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and universal tensile testing machine. The findings indicate that the incorporation of POSS into SRs results in significant enhancements in thermal stability and mechanical properties when compared to the control group (TEOS/SR). SRB and SRH exhibit the highest cross‐linking density and tensile strength. Specifically, SRB‐4 demonstrates the highest tensile strength at 2.66 MPa, representing an 8.6‐fold increase compared to TEOS/SR. The maximum decomposition rate temperature of SRP‐4 reaches 527°C and is 194°C higher than TEOS/SR. Because the alkoxy groups with different chain lengths on POSS have different chemical reactivity, they have a great effect on the dispersion of POSS in SRs, which affect the cross‐linking density, tensile strength, and thermal stability. [ABSTRACT FROM AUTHOR]