Ultimate Strain Values Research Articles

Influence of fiber shapes on the compressive behaviors of ultra-high performance concrete containing coarse aggregate

The addition of coarse aggregate in ultra-high performance concrete (UHPC-CA) has the potential to reduce autogenous shrinkage and improve mechanical properties. However, it also affects the fiber distribution and crack propagation, thereby compressive relationship of UHPC. This study investigated the effects of different fiber shapes on the compressive behaviors of UHPC-CA. Three fiber shapes (straight fiber, hooked fiber, and hybrid fiber) and six coarse aggregate content (0 - 1200 kg/m3) are the main variables. The test results have indicated that the addition of coarse aggregate in UHPC rendered wider main cracks. Hybrid fiber was preferred over the hooked-end and straight fibers to optimize ductility in UHPC-CA. An increase in compressive strength of up to 17.7% and elastic modulus of UHPC of up to 23.7% after moderate addition of coarse aggregate contents, The fiber shape affected peak strain and ultimate strain values for UHPC-CA. Their peak and ultimate strains were improved by 12.8% - 15.3% and 38.2%-127.4% with the inclusion of 2% hooked and hybrid fibers. Based on the experimental data and relevant equations, a proper rational equation from the existing literature is used to generate the complete compressive stress-strain curves of UHPC-CA with different fiber shapes. In summary, this study establishes that hybrid fiber shapes significantly enhance the compressive properties of UHPC-CA. The high elastic modulus and ductility of the UHPC-CA with hybrid fiber are particularly promising for blast and impact applications.

Bond stress-slip models and behavior of externally bonded aluminum alloy (AA) plates to concrete surface

This paper aims to assess the feasibility of employing high strength aluminum alloys (AA) with a rough (R) surface as externally bonded reinforcement (EBR) material. A comprehensive experimental investigation was carried out to evaluate the bond strength and behavior through single shear tests. The variables considered were concrete strength and bonded length, while the remaining parameters were kept constant. The study measured the ultimate load, extension, and strain values, and subsequently calculated the bond stress and slip. It was observed that the ultimate load, bond stress, and failure modes exhibited variations depending on the concrete strength and bond length. For a concrete strength of 60 MPa and a bonded length of 80 % of the concrete prism length, the ultimate load and maximum bond stress increased by 54.0 % and 66.0 % respectively, compared to those with a concrete strength of 20 MPa and the same bonded length. Additionally, when comparing a bonded length of 80 % (200 mm) of the concrete prism length to a bonded length of 20 % (50 mm), the ultimate load and maximum bond stress increased by 20.0 % and 99.0 % respectively for a concrete strength of 60 MPa. The study also developed bond stress-slip models for the AA-concrete interface, as well as models for predicting the ultimate load based on concrete strength and bonded length. These models displayed high accuracy in their predictions. In conclusion, the results indicate that AA plates are effective and suitable as EBR materials for the reinforcement of RC members.

Compressive performance of underwater concrete piers reinforced with prefabricated FRP shells

A novel underwater spliceable basalt fiber-reinforced polymer (BFRP) shell-confined concrete structure was proposed that rapidly reinforces underwater piers by lapping the FRP shell with adhesive underwater combined with nondispersive mortar (NDM) filling. Thirty-six prefabricated BFRP shells combined with nondispersive mortar reinforced concrete columns (PFRCs) were made for axial compression testing. The effects of the BFRP layer number, lap length and pouring environment on the specimen performance were compared, and different damage patterns and stressstrain relationship curves were obtained. The test results reveal that the PFRCs exhibited two failure modes: BFRP fracture failure in nonlapped segments and BFRP bond adhesive peeling failure in lap segments, and the specimens with more BFRP layers and shorter lap lengths were prone to BFRP bond adhesive peeling failure. From 2 to 4 layers, the ultimate stress and ultimate strain values increased by 1.18–1.91 times and 5.18–10.32 times, respectively, demonstrating increasing the number of BFRP layers is a more effective means to improve the structural performance. The ultimate strength of the underwater reinforced specimens reached more than 70 % of that of the corresponding specimens on land, which demonstrated the feasibility of using prefabricated FRP-molded shell reinforcing technology for submerged piers. Finally, the calculation model of an FRP-confined concrete column is evaluated, and the full stressstrain curves of the PFRCs are proposed.

Stress-Strain State of Steel Fiber-Reinforced Concrete under Compression Taking into Account Unloading from Inelastic Region

The purpose of the study is to examine the physical and mechanical characteristics of steel fiber-reinforced concrete under compression, including: modulus of elasticity, Poisson ratio, values of ultimate strains under compression, values of compressive strength with different percentages of dispersed reinforcement. An experimental investigation program, which included the production of cube samples measuring 100×100×100 mm, as well as a compression test under static loading, taking into account unloading from the region of inelastic deformations, was developed and carried out. Two types of steel fiber were chosen as dispersed reinforcement: hooked end and wave shape. The volume content of steel fiber in the cube samples was 0.5, 1.0, 1.5 and 2.0 %. As a result of the investigation, the strength and deformation characteristics of steel fiber reinforced concrete under compression were obtained. Based on the experimental data, actual strain diagrams of steel fiber reinforced concrete were constructed, taking into account the type of reinforcing fibers and the percentage of reinforcing fiber. Based on the obtained diagrams, a law of deformation of steel fiber reinforced concrete is proposed, which can be described by a polynomial function of the fourth order with constant coefficients that determine the shape of the stress-strain curve. The presented research results can be used in developing a methodology for physically nonlinear analysis of steel fiber reinforced concrete elements with a percentage of dispersed reinforcement from 0.5 to 2.0 %.

Effects of heat treatment on tensile properties of 3D-printed short fiber-reinforced composites

3D-printed carbon fibre-reinforced composites (CFRC) using fused deposition modelling (FDM) offer the potential for building complex geometries and low waste. However, these composites have weaker interlaminar bonding and higher void content than traditional composites. This paper explores the effect of temperature on improving the mechanical properties of 3D-printed short carbon fibre- reinforced polyamide (PACF). Two types of printed structures were tested: one with a 0° build orientation (parallel to extruder movement) and the other with a 90° build orientation (perpendicular to extruder movement). Both samples were heat-treated at 150°C. Force vs. displacement data was obtained from the MTS testing machine. After that, the tested samples were viewed under an optical microscope. Images obtained from the optical microscope are then analyzed to see how the samples failed by checking the microstructure. The average ultimate strength, ultimate strain, and elastic modulus were used for the analysis. The sample follows a trend where the strength and elastic modulus increase after heat treatment. The result also showed that the 0° build orientation samples have higher mechanical performance than the 90° build orientation sample. Also, from the ultimate strain values, it was evident that samples printed in the 0° absorbed more energy, exhibiting 83% higher resistance before final failure. Lastly, an optical microscope was used to investigate the failure mechanisms of the samples.

Evaluating the axial compression behaviour of hollow concrete block masonry walls with small-size openings: Various opening positions and their influence on experimental results

Openings such as windows or channels for ventilation and heating systems are commonly encountered in masonry buildings to meet with functional needs. Although these openings are known to reduce the strength and stiffness of masonry walls, however, the relationship between the position of openings and load bearing capacity of masonry walls is not well understood. Therefore, the primary aim of this study is to investigate the effect of double opening positions on the axial compressive behaviour of masonry walls constructed with hollow concrete block units. Seven one-half scale walls with different double opening positions were constructed using hollow concrete block units and subjected to a uniformly distributed axial load. The compressive performance such as the strength, stiffness, load-deformation behaviour, stress-strain response, cracking pattern and failure behaviour of the walls have been reported. The results indicate that the 50% reduction in sectional area ratio caused by introducing two small openings in the walls reduced the load bearing capacity by 36 to 50%. Measured ultimate strain values ranges between 5.5 to 38.8% reduction in walls with openings compared with the wall without opening. Vertical cracking, face spalling, and block rupture were the dominant failure modes for walls with double openings, in contrast to mainly vertical cracks observed in the solid wall. This research provides valuable insights into how the positions of double openings influence the performance and overall structural response of hollow concrete block masonry walls under compression load.

Design of Near α-Ti Alloys with Optimized Mechanical and Corrosion Properties and Their Characterizations

The designed alloy Ti-10.56%Al-2.08%Zr-0.80%Sn-0.88%Mo-0.51%Si (mol%), modified alloy Ti-10.81%Al-4.80%Zr-1.23%Sn-0.76%Cu-0.35%Si (mol%) and reference alloy Ti-10.52%Al-2.07%Zr-1.1%Sn-0.2%Mo-0.76%Si (mol%) with the same bond order (Bot) value of 3.49 and different d-orbital energy level (Mdt) values of 2.43, 2.42 and 2.42 were proposed and their mechanical and corrosion properties were compared in the present study. The ultimate tensile strength (σUTS) and fracture strain (ɛf) values of the three near α-Ti alloys at both as-cast and solution-treated conditions were 989 and 1118 MPa and 11.6% and 3.4% for the designed alloy, 993 and 1354 MPa with 13.5% and 2.3% for the modified alloy and 991 and 1238 MPa with 12.7% and 3.1% for the reference alloy, respectively. The thickness of corrosion layers of the solution-treated designed, modified and reference near α-Ti alloys after immersion in hot salts for 28.8 ks were measured at 3.06, 3.68 and 4.89 µm. The comparable mechanical properties and improved hot salt corrosion resistance ability of designed and modified alloys compared to those of the reference alloy were obtained by considering their Bot and Mdt values; this might lead to the development of alternative near α-Ti alloys to conventional materials.

Explainable Data-Driven Ensemble Learning Models for the Mechanical Properties Prediction of Concrete Confined by Aramid Fiber-Reinforced Polymer Wraps Using Generative Adversarial Networks

The current study offers a data-driven methodology to predict the ultimate strain and compressive strength of concrete reinforced by aramid FRP wraps. An experimental database was collected from the literature, on which seven different machine learning (ML) models were trained. The diameter and length of the cylindrical specimens, the compressive strength of unconfined concrete, the thickness, elasticity modulus and ultimate tensile strength of the FRP wrap were used as the input features of the machine learning models, to predict the ultimate strength and strain of the specimens. The experimental dataset was further enhanced with synthetic data using the tabular generative adversarial network (TGAN) approach. The machine learning models’ performances were compared to the predictions of the existing strain capacity and compressive strength prediction equations for aramid FRP-confined concrete. The accuracy of the predictive models was measured using state-of-the-art statistical metrics such as the coefficient of determination, mean absolute error and root mean squared error. On average, the machine learning models were found to perform better than the available equations in the literature. In particular, the extra trees regressor, XGBoost and K-nearest neighbors algorithms performed significantly better than the remaining algorithms, with R2 scores greater than 0.98. Furthermore, the SHapley Additive exPlanations (SHAP) method and individual conditional expectation (ICE) plots were used to visualize the effects of various input parameters on the predicted ultimate strain and strength values. The unconfined compressive strength of concrete and the ultimate tensile strength of the FRP wrap were found to have the greatest impact on the machine learning model outputs.

Shrinkage performance and modelling of concretes incorporating crushed limestone sand with a high content of fillers for pavement slabs

Because of the gradual depletion of gravel and river sand resources and restrictions on quarrying activities to maintain the ecological balance, limestone crushed sand with a high content of limestone fillers is being explored to be used, as an alternative source of supply, in Portland cement concrete (PCC) for rigid pavement. This paper aims to first present mechanical test results carried out on three types of PCC formulated with crushed limestone sand as fine aggregates, devoid of superplasticizers. Since shrinkage cracking is an important problem for rigid pavement, the shrinkage behaviour of these concretes is then experimentally investigated. Furthermore, three existing models (ACI-209, Eurocode2, and triple-sphere models) and a novel-developed model are used to estimate the mixtures’ shrinkage. Results showed that the designed mixtures exhibited normal shrinkage values. The shrinkage modelling revealed that the proposed model well fitted the experimental data. Besides, Eurocode2 and ACI-209 models may be adapted for the case of limestone concretes containing a high content of limestone fillers and then used to accurately estimate their shrinkage strains. However, the triple-sphere model was unsuitable for these concretes and overestimated their ultimate shrinkage since it does not take into account their high filler content. Nevertheless, by adjusting the paste shrinkage expression, the ultimate shrinkage strain values of the tested mixtures were improved.

Material and construction solutions in the construction of civil defence shelters

An analysis is presented of the use of material and construction solutions used in construction, mainly residential, for the construction of OC (civil defence) shelters.The article presents procedures for designing reinforced concrete structures that make it possible to properly determine the load capacity of critical sections. In the present work, a study of the deformation stability of a zone of reinforced concrete sections that is subjected to compression is used. Computational methods based on Drucker's postulate were used to solve the problem. The proposed approach enables the determination of the values of ultimate and failure strains based on the analysis of the loading path of a reinforced concrete section.Generally, shelters built into residential buildings are analysed, intended to be constructed in the rooms of the basement floor. A reduced need for ancillary space, the basement room, is observed. Garage functions are located on the basement floor. The plan contours of the basement are often larger than those of the ground floor. It is possible to design a shelter for the residents of the building, which ensures the greatest efficiency in its use. It is desirable to maintain uniform material and construction solutions while maintaining technological and organisational solutions during the erection of the entire building.The paper indicates the possibility of using some of the material and structural solutions of the housing construction in the realisation of OC shelters built into the basement floor. The construction of free-standing shelters was not analysed separately, but the proposals presented in the paper can also be applied to the type of OC shelters. Some results of the analysis of the adaptation of material and structural solutions of the housing construction to the needs of OC shelters construction will be presented during the symposium.It is advisable to develop models for the construction of OC shelters using contemporary technologies used in the construction industry.Useful tool can be the proposed scheme for improving activities based on the EFQM model.

Axial compressive behavior of green sustainable Water Hyacinth & Bio-Resin (WHBR) FRP composites-confined circular concrete

This study examines the behavior of circular concretes externally confined by green sustainable WHBR FRP containing water hyacinth fiber ropes and bio-resin. This study principally purposes to discover the axial stress-strain relationship behavior of WHBR FRP-confined circular concrete. A total of 10 circular concretes with a dimension of 150×300 mm were cast, strengthened with one to four layers of WHBR FRP, and tested under compression. The stress and the deformability of WHBR FRP-confined circular concretes were observed to be increased along with the addition of WHBR FRP layers. The accurateness of existing ultimate stress and strain models of natural FRP-confined circular concrete was evaluated using the test results. Indicating the need for the newly developed models to precisely predict the ultimate stress and strain values of WHBR FRP-confined circular concrete, newly developed models were developed to be precise in estimating the ultimate stress and strain of WHBR FRP-confined circular concrete. Keywords concrete, confinement, disaster risk reduction, stress-strain, water hyacinth fiber.

Evaluation method of surrounding rock stability: Failure approach index theory of strain limit analysis for engineering applications.

In general, the ultimate parameter selection method of the failure approach index theory among the three-dimensional problems in geotechnical engineering is unclear in theory, and the symbol convention of the failure approach index in engineering calculation is contrary to the stipulation of the numerical simulation software. Hence, the values of the ultimate plastic shear strain are difficult to determine. To solve this problem, the criterion of positive tension and negative compression and the sequence of the principal stress σ1 ≤ σ2 ≤ σ3 are defined in this paper, and the expression of Mohr-Coulomb yield approach index id deduced. Under the condition of the principal strain sequence ε1 ≤ ε2 ≤ ε3, the formula of the ultimate shear strain is derived using the method of the ultimate strain analysis so as to obtain the simple expression and calculation method of the ultimate plastic shear strain, which has provided the calculation parameters for the three-dimensional ultimate plastic shear strain in the Mohr-Coulomb strain softening model and improved the failure approach index theory. In the light of the aforementioned theory, the ultimate strains of cubic concrete specimens are analyzed, and the obtained ultimate strain values are found consistent with previous research findings, which verifies the correctness and reliability of the ultimate strain analysis method. In addition, it is applied to the quantitative elastic-plastic failure analysis of the section coal pillar in Hengjin coal industry for determining its reasonable retainment width. Consequently, the research results can be embraced as the theoretical basis for the stability analysis of geotechnical materials and exhibits engineering application potential.

Evaluating the performance of ReaxFF potentials for sp2 carbon systems (graphene, carbon nanotubes, fullerenes) and a new ReaxFF potential.

We study the performance of eleven reactive force fields (ReaxFF), which can be used to study sp2 carbon systems. Among them a new hybrid ReaxFF is proposed combining two others and introducing two different types of C atoms. The advantages of that potential are discussed. We analyze the behavior of ReaxFFs with respect to 1) the structural and mechanical properties of graphene, its response to strain and phonon dispersion relation; 2) the energetics of (n, 0) and (n, n) carbon nanotubes (CNTs), their mechanical properties and response to strain up to fracture; 3) the energetics of the icosahedral C60 fullerene and the 40 C40 fullerene isomers. Seven of them provide not very realistic predictions for graphene, which made us focusing on the remaining, which provide reasonable results for 1) the structure, energy and phonon band structure of graphene, 2) the energetics of CNTs versus their diameter and 3) the energy of C60 and the trend of the energy of the C40 fullerene isomers versus their pentagon adjacencies, in accordance with density functional theory (DFT) calculations and/or experimental data. Moreover, the predicted fracture strain, ultimate tensile strength and strain values of CNTs are inside the range of experimental values, although overestimated with respect to DFT. However, they underestimate the Young’s modulus, overestimate the Poisson’s ratio of both graphene and CNTs and they display anomalous behavior of the stress - strain and Poisson’s ratio - strain curves, whose origin needs further investigation.

Durability of Acrylic Products during Heat Aging

Currently, the areas of application of polymethyl methacrylate plastic (acrylic) owing to its unique properties (most notably, lightness, plasticity, exceptional transparency and high impact resistance) range widely from modeling, lighting technology and medicine, automotive industry and watchmaking to aviation, shipbuilding, rocket engineering and production of military equipment. Mechanical characteristics of polymethyl methacrylate plastic, like most polymers, change significantly over time when exposed to temperature. The temperature impact extends to all volume of the material and leads to its “heat aging”, which should be considered when designing the products made of polymethyl methacrylate plastic. The process of thermal destruction is long enough, so it is reasonable to predict the changes in the properties of polymethyl methacrylate plastic using accelerated methods of material specimen aging with subsequent testing under simple loading. The paper deals with the experimental study of the process of changing of physical and mechanical characteristics of polymethyl methacrylate plastic during thermal destruction. Heat aging of the material is identified with the process of the thermal oxidative destruction occurring at a constant rate and specified temperature. It is assumed that the change in polymer’s mechanical properties is proportional to the change in number of its functional groups. The tests were performed on cylindrical specimens with fillets at the ends at three levels of temperature: 40, 70 and 100°C. Specimens were held at each temperature for 2; 5; 10; 20 and 30 days. According to results of statistical processing of experiments, we obtained the average values of ultimate strains for each temperature-time regime. The obtained ultimate strain values were the basis for the construction of long-term aging curves. For the minimum allowable value of ultimate strain in operation, the period of operation of polymethyl methacrylate plastic was determined for different aging temperatures. At the operating temperature of 20oС the period of operation was 12 years. During this period, the ultimate deformability of polymethyl methacrylate plastic decreases to 3%, which is approximately equal to elastic deformations. The results will allow us to predict the period of operation of polymethyl methacrylate plastic products for different values of the ultimate strain and operating temperature.

Using Strain Energy Method to Estimate Buckling in Steel Column AISI 1312 during Effects of Fire Hazard

A Group of three specimens from 1312 steel were subjected to a range of elevated temperatures (700, 800, 900) Celsius to demonstrate the hazard of fire on steel columns mechanical proprieties. The results show a dangerous increase in creep strain buckling after 60 minutes from the beginning of the test and after 67 minutes failed to occur. Mechanical tests for normal and elevated temperatures were made to compare the fire hazards, the results depict reduction by 29%, 46%, 55% for young modulus of elasticity for elevated steel specimens (700, 800, 900) °C. for yield strength the value decreased by (128.4, 169.6, 189) Mpa for specimens (700, 800, 900) °C respectively. The ultimate stress reduction by (64, 78, 83) % from the normal value. whenever higher temperatures go up the lower the ultimate strain falls dawn by (50, 60, 66) % to the original ultimate strain value 0.5. the 0.2 strain % is decreased from 0.0029 to 0.0027 for 700 °C and increased to 0.011, 0.015 for (800, 900) °C respectively.

COMPRESSIVE CYLINDER STRENGTH AND DEFORMABILITY OF EXPANDED CLAY FIBER-REINFORCED CONCRETE WITH POLYPROPYLENE FIBER

This article presents the experimental studies results of the reinforcement effect with polypropylene fiber (0.5 %, 1 %, and 1.5 %) on the strength (compressive cylinder strength) and deformation (compressive strain) characteristics for expanded clay concrete. The most effective fiber percentage is the content of 1.5 % by weight of the cement mass, based on obtained experimental results. An increase in the compressive cylinder strength (up to 13 %), a significant increase in the value of ultimate compressive strain in concrete (corresponding to the peak stress) of the stress-strain diagram (up to 50 %), and the plastic failure of expanded clay fiber-reinforced concrete is noted.

Synergistic effect of cellulose nanocrystals-graphene oxide as an effective nanofiller for enhancing properties of solventless polymer nanocomposites

The solution mixing approach-based cellulose nanocrystals (CNCs) decorated graphene oxide (GO) nanohybrids (CNC@GO) was prepared and their effect over on the solventless polymer (SLP) called waterborne epoxy system was analyzed. The as-prepared GO, CNC and CNC@GO were scrutinized by several characterization techniques such as X-ray diffraction (XRD), thermogravimetric analysis (TGA), Raman Analysis, Fourier transform infra-red (FT-IR), transmission electron microscopy (TEM) and field emission scanning electron microscope (FESEM) for identifying their quality. The GO-SLP, CNC-SLP and CNC@GO-SLP nanocomposites mechanical and thermal properties were analyzed in detail. The highest tensile strength was observed at the lowest loading content (0.2 wt %) of CNC@GO incorporated SLP nanocomposites, as compared with other (0.2 wt % of (GO-SLP and CNC-SLP)) nanocomposites. Also, the thermo-mechanical analysis of CNC@GO nanohybrids incorporated SLP system exposes a notable improvement in the tan delta and storage modulus values at lower nanofiller concentration (0.2 wt %). The successful decoration of CNC on the GO surface promotes to the uniform dispersion, strong hydrogen bonding and outstanding interaction between the introduced nanofillers within the SLP system which leads to the better results in the mechanical and thermal properties. Besides, it was observed that the numerical simulation responses were in good deal with the laboratory values for both ultimate stress and strain. Thus, the as-prepared nanohybrids could possibly enrich the mechanical and thermal properties of the SLP system.

Vat Photopolymerization of Reinforced Styrene-Butadiene Elastomers: A Degradable Scaffold Approach.

Vat photopolymerization (VP) is a high-throughput additive manufacturing modality that also offers exceptional feature resolution and surface finish; however, the process is constrained by a limited selection of processable photocurable resins. Low resin viscosity (<10 Pa·s) is one of the most stringent process-induced constraints on resin processability, which in turn limits the mechanical performance of printed resin systems. Recently, the authors created a VP-processable photosensitive latex resin, where compartmentalization of the high molecular weight polymer chains into discrete particles resulted in the decoupling of viscosity from molecular weight. However, the monomers used to form the hydrogel green body resulted in decreased ultimate material properties due to the high cross-link density. Herein, we report a novel scaffold that allows for facile UV-based AM and simultaneously enhances the final part's material properties. This is achieved with a chemically labile acetal-containing cross-linker in conjunction with N-vinylpyrrolidone, which forms a glassy polymer after photocuring. Subsequent reactive extraction cleaves the cross-links and liberates the glassy polymer, which provides mechanical reinforcement of the geometrically complex VP-printed elastomer. With only a 0.1 wt % loading of photoinitiator, G'/G'' crossover times of less than 1 s and green body plateau moduli nearing 105 Pa are obtained. In addition, removal of the hydrophilic and thermally labile scaffold results in decreased water uptake and increased thermal stability of the final printed part. Ultimate strain and stress values of over 650% and 8.5 MPa, respectively, are achieved, setting a new benchmark for styrene-butadiene VP elastomers.

Manufacturing and Modeling of Polypropylene-based Hybrid Composites by Using Multiple-Nonlinear Regression Analysis

In this research, artichoke stem particles (AS) and wollastonite (W) were used as an organic and inorganic fillers in order to improve the mechanical properties of polypropylene (PP). In this regard, PP-matrix composites containing AS and W were produced as non-hybrid and hybrid using a high speed thermo-kinetic mixer. Mechanical properties of polymer composites were investigated by the tensile test. Experimental results reveal that the highest modulus of elasticity was obtained in PP-W and the highest tensile strength was obtained in raw PP while the lowest ultimate strain value was obtained in PP-W-AS. Then, multiple-nonlinear regression analysis was employed to determine the effect of weight ratios of W and AS in PP on modulus of elasticity, tensile strength and ultimate strain. Experimental results were expressed with polynomial, rational and trigonometric models. The results show that the proposed models have well fitted with the experimental results. The coefficient of determination (R2) values were found between 0.95 and 1 in all models. Also, boundedness check control of the proposed models which gives information about whether models are realistic or not was carried out by calculating the maximum and minimum values produced by the relevant model.

Strain engineering of electronic and optical properties of monolayer diboron dinitride

We studied the effect of strain engineering on the electronic, structural, mechanical, and optical properties of orthorhombic diboron dinitride (o-${\mathrm{B}}_{2}{\mathrm{N}}_{2}$) through first-principles calculations. The 1.7-eV direct band gap observed in the unstrained o-${\mathrm{B}}_{2}{\mathrm{N}}_{2}$ can be tuned up to 3 eV or down to 1 eV by applying 12% tensile strain in armchair and zigzag directions, respectively. Ultimate strain values of o-${\mathrm{B}}_{2}{\mathrm{N}}_{2}$ were found to be comparable with that of graphene. Our calculations revealed that the partial alignment of the band edges with the redox potentials of water in pristine o-${\mathrm{B}}_{2}{\mathrm{N}}_{2}$ can be tuned into a full alignment under the armchair and biaxial tensile strains. The anisotropic charge carrier mobility found in o-${\mathrm{B}}_{2}{\mathrm{N}}_{2}$ prolongs the average lifetime of the carrier drift, creating a suitable condition for photoinduced catalytic reactions on its surface. Finally, we found that even in extreme straining regimes, the highly anisotropic optical absorption of o-${\mathrm{B}}_{2}{\mathrm{N}}_{2}$ with strong absorption in the visible range is preserved. Having strong visible light absorption and prolonged carrier migration time, we propose that strain engineering is an effective route to tune the band gap energy and band alignment of o-${\mathrm{B}}_{2}{\mathrm{N}}_{2}$ and turn this two-dimensional material into a promising photocatalyst for efficient hydrogen production from water splitting.