Tensile Stress-strain Behavior Research Articles

A novel methodology to determine tensile properties in the heat-affected zone of tailor welded blanks with different base material thicknesses

When testing the mechanical properties of a tailor welded blank (TWB) under uniaxial tension, the localized bending moment generated by eccentric loading, due to the change in thickness between the welded sheets, causes the experimentally measured stress-strain behavior to not match the actual stress-strain behavior. In this paper, a new method to calibrate the tensile stress-strain behavior in the heat affected zone (HAZ) of a TWB with different thicknesses is proposed based on indentation testing and tensile test with multi-camera digital image correlation (DIC). The nominal stress-strain curve is calculated for calibration purposes. The nominal strain is obtained by performing multiple linear regression analysis on the front and back surface strains of the HAZ provided by the multi-camera DIC system. Experiments were conducted using this method on a TWB of the same material (DP1180) and different thicknesses (1 mm and 1.4 mm). The validation of the corrected stress-strain curves demonstrated the reliability and effectiveness of the proposed method.

PET particles modify strain hardening cementitious composites: An approach to introduce defects to enhance deformation capacity

Enhancing deformation capabilities remains a critical direction in the research of Strain-Hardening Cementitious Composites (SHCC). This investigation introduces Polyethylene Terephthalate (PET) particles as a novel method to induce micro-defects within SHCC, aiming to reduce the material's initial crack strength and improve its deformability. Through the exploration of various PET particle volumetric substitutions for traditional aggregates, the development of PET particle-modified SHCC (PMSHCC) was achieved. The paper examines the impact and mechanisms of different PET volumetric substitution rates (0 %, 5 %, 10 %, 15 %, 20 %, and 25 %) on the workability, axial compression strength and tensile properties of PMSHCC. By employing Digital Image Correlation techniques, the progression of crack width and density in PMSHCC under tensile load was documented, facilitating an analysis of the influence mechanisms of varying PET volumetric substitution rates on the tensile strain-hardening behavior of PMSHCC. The findings indicate that the increased Interfacial Transition Zone (ITZ) thickness between PET particles and the cement matrix, combined with the lower elastic modulus of PET particles compared to the cement matrix and quartz sand, collectively contribute to a reduction in tensile initial crack strength and an enhancement in ultimate tensile strain of PMSHCC. Within the examined range, an increase in the PET volumetric substitution rate significantly improves the ultimate tensile strain of PMSHCC by up to 76.0 %, with a minimal reduction in tensile strength of only 3.99 %. Moreover, the study proposes a tensile linear strengthening elasto-plastic model for PMSHCC incorporating the PET substitution rate, enabling accurate prediction of the material's tensile stress-strain behavior. These findings not only offer a novel pathway for the utilization of waste plastics but also provide significant insights for enhancing the deformability of SHCC.

Tensile Mechanical and Stress-Strain Behavior of Recycling Polypropylene Fiber Recycled Coarse Aggregate Concrete

Tensile Mechanical and Stress-Strain Behavior of Recycling Polypropylene Fiber Recycled Coarse Aggregate Concrete

Green engineered cementitious composites with enhanced tensile and flexural properties at elevated temperatures

This study provides new insights in the design of green hybrid polyethylene (PE)-steel fibre reinforced high strength engineered cementitious composite (HSECC) with superior tensile and flexural strength at both ambient and elevated temperatures. Blends of high volume of ground granulated blast furnace slag (GGBFS), dolomite powder and fly ash were utilized to achieve a 60 % cement replacement for the HSECC mixes. These mixes were then exposed to 20–600 °C and a total of 210 specimens were tested to assess their residual tensile stress–strain behaviour, flexural load–displacement response, and toughness. Results indicate that high volume of GGBFS can be very effective in limiting the surface damage and retaining high strength at elevated temperatures. A combination of 1.5 % PE-0.75 % steel with quaternary blend of GGBFS, dolomite and fly ash demonstrated at least 60 % and 40 % retention in tensile and flexural strength at 600 °C, respectively. This was significantly better than the strength of the traditional control silica fume mix considered in this study as well as results reported in many previous literatures on HSECC. Microstructural examination was further conducted to understand the mechanism of fibre deterioration and justify the resulting change in pseudo-hardening behaviour with temperature rise. Findings obtained in this study clearly demonstrated the effectiveness of PE-steel fibre hybridisation at elevated temperature and confirmed that with right binder selection, superior tensile and flexural performance can be achieved even with a very high cement replacement level.

Root anatomy and biomechanical properties: improving predictions through root cortical and stele properties

PurposeQuantifying the stability of individual plants or their contribution to soil reinforcement against erosion or landslides requires an understanding of the tensile properties of their roots. This work developed a new analytical model to understand the tensile stress–strain behaviour of a single root axis, which is the first to incorporating root anatomical features, in order to reduce the existing uncertainty in predictions.MethodsThe root was modelled as a linear elastic stele connected to a surrounding linear elastic cortex by means of a linear elastic stele–cortex interface. By solving for force equilibrium, an analytical solution for the full tensile stress–strain behaviour — including any intermediate brittle failures of the stele, cortex and/or interface — was obtained. This model was compared to tensile tests and laser ablation tomography for maize roots.ResultsThe new modelling approach demonstrated that the root tensile strength is fully determined by the strength of the stele alone, which was an order of magnitude larger than that of the cortex while also 3–4 times stiffer. The reduction in root stiffness beyond the yield point was linked to continuing fracturing of the cortex and debonding along the stele–cortex interface. A larger proportion of the variation in experimentally measured biomechanical characteristics could be explained compared to root diameter power-law fitting methods typically applied in the literature.ConclusionStele and cortex biomechanical properties are substantially different, affecting the tensile behaviour of plant roots. Accounting for these anatomical traits increased the accuracy root biomechanical properties from tensile tests.

Upgrading seismic performance of beam-column joints using steel-polypropylene hybrid fiber: Experiment and numerical simulation

Due to the exceptional resistance to concrete cracking, appropriate incorporation of steel-polypropylene hybrid fiber is anticipated to enhance the mechanical properties of beam-column joints that are crucial for ensuring the integrity of frame structures under earthquake excitations. In this study, twenty-eight steel-polypropylene hybrid fiber reinforced concrete beam-column joints (HFRC-BCJs) were tested under cyclic loading to investigate their seismic performance, in which the effects of fiber types, concrete strength, axial compression ratio, and characteristic parameters of hybrid fiber are taken into account. The results indicated that the incorporation of steel-polypropylene hybrid fiber can exert a beneficial synergetic effect on improving the seismic responses of beam-column joints in multiple aspects. Specifically, hybrid fiber not only alleviated the concrete damage within the core region significantly, but also augmented the initial cracking load, displacement ductility coefficient, and energy dissipation coefficient of the beam-column joints by an average of 40.5 %, 31.4 %, and 37.3 %, respectively. Moreover, with the purpose of enabling a reasonable prediction of the seismic responses of HFRC-BCJs, a modified super degree-of-freedom (DOF) element was adopted for the numerical simulation, in which a user-defined UMAT subroutine was developed to more accurately reflect the enhancements of fiber inclusion on the tensile and compressive stress-strain behaviors of HFRC, as well as the associated damage evolution.

Fracture behavior of concrete made with sintered fly ash lightweight coarse aggregate in comparison to normal weight concrete

Sintered fly ash lightweight aggregate based concrete has been reported to give mechanical and durability properties similar to conventional concrete. But concrete made up of lightweight aggregate possesses lower stiffness and shear strength resulting into a brittle mode of failure due to crack propagating directly inside aggregate which is weak in nature. The study presents findings from the experimental investigation of fracture behavior of concrete made with sintered fly ash lightweight coarse aggregate in comparison to normal weight concrete (NWC) at w/b ratio of 0.5, 0.4 and 0.3. The mixes have been tested for compressive and split tensile strength for both concrete types. On notched beams of size 100x 100 x 500 mm, a three-point bend test has been carried out for both lightweight and normal weight concrete to evaluate fracture parameters. The results of split tensile strength test indicated that the split tensile to compressive strength ratio lies in the range of 5-8% for lightweight concrete and this ratio lies between 5-10% for normal weight concrete. The study indicates comparable fracture behavior for both lightweight and normal weight concrete. The non-linear ascending and descending branches in load vs deflection curve of concrete with sintered fly ash lightweight coarse aggregate can be linked with the non-linearity in tensile type stress-strain behavior and formation of the fracture zone in front of the initial notch. The modulus of elasticity of lightweight concrete is significantly lower than normal concrete. The modulus of elasticity, area under the load deflection curve, tensile strength, fracture behavior etc. needs to be considered appropriately in the non-linear analysis of lightweight concrete.

Coarse synthetic fibers (PP and POM) as a replacement to steel fibers in UHPC: Tensile behavior, environmental and economic assessment

Ultra-high performance concrete (UHPC) has excellent compressive strength and ductility. Nevertheless, the extensive utilization of UHPC has been impeded by factors including the exorbitant cost, substantial carbon emissions, and vulnerability to corrosion associated with steel fibers. This study explores an innovative approach by introducing polypropylene fibers (PPF) and polyoxymethylene fibers (POMF) as replacements for steel fibers (SF) in the preparation of hybrid fiber-reinforced ultra-high-performance concrete (HUHPC), with a total fiber content of 3% vol. The influence and mechanism of different PPF/POMF replacement ratios for SF on the flowability, compressive performance, and tensile behavior of HUHPC were investigated. An axial tensile static constitutive model for HUHPC considering the PPF/POMF replacement ratio was established, and a comprehensive environmental benefit assessment index and economic benefit assessment index considering mechanical performance were proposed. The results showed that using PPF and POMF with low modulus as replacements for high-modulus SF significantly improved the flowability of HUHPC. Notwithstanding there is a decrease in compressive and tensile strength of HUHPC resulting from the utilization of low-modulus and low-strength PPF and POMF as substitutes for SF, it modified the axial tensile stress-strain behavior of conventional UHPC and notably improved its tensile toughness. The established axial constitutive model for HUHPC in this study effectively predicted the tensile stress-strain behavior of HUHPC. Importantly, the comprehensive environmental assessment index reveals that HUHPC offers superior environmental and economic benefits compared to traditional UHPC, leading to substantial cost reductions. The development of HUHPC through fiber hybridization presents a promising strategy for the low-carbon and cost-effective production of UHPC, holding significant implications for the broader adoption and application of UHPC.

Achieving low tension-compression yield asymmetry and ultrahigh strength in Mg–1Al–1Ca–0.2Mn (wt%) alloy via sub-micron grain refinement

Traditional low-alloyed Mg–Al–Ca–Mn extrusion alloys always show a low strength and a high tension-compression yield asymmetry. In the present work, Mg–1Al–1Ca–0.2Mn (AXM1102, wt.%) alloys were extruded at 150–350 °C to produce different grain structure and mechanical properties. It is shown that AXM1102-150 (extruded at 150 °C) sample exhibits superhigh strength in both tension and compression, which exhibited a yield strength (YS) of 428 MPa in tension and 416 MPa in compression. Namely, ultrahigh strength and low tension-compression yield asymmetry were both obtained. The ultrahigh strength was found to be ascribed to the ultra-fine dynamically recrystallized (DRXed) grains (0.47 μm) together with grain boundary co-segregation of Ca and Al atoms. Submicron DRXed grains accounts for the improved tension-compression yield asymmetry through suppressing {10-12} twining during compression. Additionally, the discontinuous yielding was detected during tension of AXM1102-150 alloy, which is potentially related with the high energy barrier required for dislocation emission caused by grain boundary co-segregation of Al and Ca atoms. Once the tensile stress reaches the peak value, the mobile dislocation density increases immediately, thus the tensile stress-strain behavior of the AXM1102-150 alloy is dominated by strain softening. The results indicate that low-alloyed Mg–Al–Ca–Mn alloys demonstrate tremendous potential as next generation ultrahigh-strength and low tension-compression yield asymmetry wrought Mg alloys.

Mechanical Behavior of Seamless Pipes Using Ring Expansion Technique and Novel Hoop Stress Correlation Factor (K)

This study investigated the stress–strain behavior of seamless pipes in the hoop direction using the ring expansion test, which is a non-standardized mechanical testing technique used for evaluating the mechanical properties of round tubes. However, this technique has limitations, such as unidentified specimen geometry, strain measurement, and the estimation of friction coefficients. The study employed experimental, numerical, and analytical methodologies to address these limitations and throughout the study, a novel hoop stress correlation factor (K) was identified to be multiplied by the hoop stress derived equation for reduced section ring specimens. The experimental strain was measured using a newly derived analytical equation, and a mathematical predictive model was developed to estimate the K-factor using the Design of Experiment (DoE) and Design-Expert statistical software. The study concluded that the ring expansion test is a promising technique for evaluating the mechanical properties of seamless pipes similar to the unified axial tensile stress–strain behavior. However, future research is needed to estimate the hoop stress correlation value (K) for all ring geometries. The study's finding of the novel hoop stress correlation factor (K) in the case of a reduced section ring specimen is particularly noteworthy, as it addresses a significant research gap in the field.

Influence of pre-strain on tensile response of extra deep drawing (EDD) steel under varying strain rates and crash performance

This study explores the impact of pre-strain on the uniaxial tensile stress-strain behavior of extra deep drawing (EDD) steel at varying strain rates. The EDD steel blanks were subjected to a uniaxial pre-strain of 15 % in either the transverse or rolling direction. Subsequently, uniaxial tensile tests were conducted at different strain rates, both orthogonal and parallel to the initial pre-straining direction. The study also investigates the alterations in yield stress (YS), ultimate tensile strength (UTS), uniform elongation (UEL), total elongation (TEL), and strain energy absorption (SED, represented by the area under the tensile stress-strain curve) at diverse strain rates after pre-straining. The experimental findings indicate that pre-straining is advantageous for enhancing YS, UTS, and SED. However, this improvement comes at the expense of UEL or TEL. A square crush tube, which shares similarities with automotive components, was examined to assess the crash performance of several automotive structural parts during crash events. A validated constitutive model was used to predict the square tube's energy absorption and crush performance under high-velocity conditions for different pre-straining scenarios.

NLFEA of one-way slabs in transition between shear and punching: Recommendations for modeling

Several studies investigated the precision of non-linear finite element analyses (NLFEA) to predict the shear capacity of beams or the punching capacity of slab-column connections. However, in the literature, there is little discussion regarding the results of NLFEA to predict the ultimate capacity and failure mechanism of slabs susceptible to different failure mechanisms. In this study, a set of tests from literature that developed different shear failure mechanisms was evaluated by NLFEA. A total of thirteen slabs were modeled, where slab’s width and shear span varied. A coupled damaged-plasticity model was employed to simulate the concrete behavior. The proposed model was calibrated to simulate specimens that failed as wide beams in one-way shear and specimens that failed by punching shear. Besides, the effect of different modeling choices was investigated: (i) the assumed stress–strain behavior in compression; (ii) tensile stress–strain behavior; (iii) the inclusion or not of damage parameters and (iv) the viscosity parameter. The results indicated that, on average, the proposed modeling strategy represented the failure mechanism and ultimate loads well. Also, the same calibrated model was found capable of representing one-way shear failure and punching shear failure or mixed modes. The sensitivity study demonstrated that the tensile stress–strain behavior and viscosity parameter influences the results of the numerical models more significantly than the assumed stress–strain behavior in compression or including/not including the damage parameters. This paper concludes that modeling strategies during the calibration process shall be checked carefully before performing any parametric analyses to identify the accuracy of the numerical models to represent the different failure mechanisms. Moreover, the validation step of the modeling strategy shall identify possible limits of the numerical model to be considered in the parametric analyses.

Cyclic tensile behavior of ultra-high performance concrete with hybrid steel-polypropylene fiber: Experimental study and analytical model

The present study deals with the effect of steel-polypropylene hybrid fiber on the tensile stress–strain behavior of ultra-high performance concrete (UHPC) subjected to monotonic and cyclic loading. Eight batches of UHPC samples with hybrid fibers were tested, with the failure process monitored by acoustic emission (AE) technique synchronously. The failure mechanism of UHPC and reinforcing mechanism of hybrid fibers were analyzed based on the combination of AE source location and scanning election microscope (SEM) observation results. The results indicated that the inclusion of hybrid steel-polypropylene fibers in UHPC matrix contributes to the enhancement of tensile mechanical performance with respect to the tensile strength, peak strain and especially the tensile toughness. Moreover, the relationship between plastic strain accumulation and envelope unloading strain during cyclic tension presents a linear pattern and appears insensitive to the variation of fiber parameters. However, the hybrid fibers significantly contribute to alleviation of the elastic stiffness degradation of UHPC during the cyclic tension. Based on the stiffness degradation process, a damage evolution law characterized by an exponential equation associated with fiber reinforcement indexes is proposed. Notably, the failure of UHPC specimen stems from concurrent macro-crack propagation and multiple cracking behavior throughout the whole loading process, which is improved due to the multi-scale reinforcement effect of hybrid fibers. Finally, in consideration of the effect of hybrid fibers, an analytical constitutive model is developed to generalize the tensile behavior of UHPC, and the comparisons yield a close estimation with test results in current research and literature.

Microstructural evolution characteristics and a unified dislocation-density related constitutive model for a 7046 aluminum alloy during hot tensile

Hot tensile features of a commercial 7046 aluminum alloy are investigated through employing high-temperature tensile tests. The evolving mechanisms of microstructures over high-temperature tensile parameters are systematically revealed. A unified dislocation-density related constitutive model is proposed to reconstruct hot tensile stress–strain behaviors. Results imply that the microstructural evolving features are acutely influenced by tensile parameters. The principal softening mechanism converts from dynamic recovery (DRV) to dynamic recrystallization (DRX), as the tensile temperature reaches 350 °C or above. The combined DRX nucleation features containing discontinuous DRX (DDRX) as well as continuous DRX (CDRX) together emerge. Furthermore, the CDRX behavior characterized by substructural nucleation and interaction becomes apparent at low tensile temperature or high strain rate, while the DDRX process is weaken. Through validation, the reproduced tensile stress, grain size as well as DRX fraction are good accordance with experimented values, which proves the proposed dislocation-density related equation can enjoy an outstanding reproduced capacity for the thermal tensile features of a 7046 aluminum alloy.

Comparative evaluation of textiles for use in textile reinforced concrete

Textile reinforced concrete (TRC) offers many advantages over traditional, steel bar reinforced concrete. The biggest advantage is the corrosion resistance of textiles, which leads to a reduced minimum cover with concrete. This allows for significantly thinner concrete elements, which are also easier to shape because of the excellent draping properties of textiles. For producers of technical textiles there is a need for a quick and easy method to test their products for suitability for use in TRC. In this paper, such a method is proposed: Novel textiles can be evaluated by comparing their properties to those of existing textiles already in use in the construction industry. Three different characteristic values crucial to the suitability of textiles for use in TRC are identified: tensile stress–strain behavior and alkaline resistance of the textiles and the tensile stress–strain behavior of TRC components. For each characteristic value a test method is identified. To validate these test methods and to provide a database for future comparison, the tests are performed on three different impregnated biaxial non-crimp fabrics that are already approved for and used in TRC. These consist of a styrene butadiene rubber impregnated carbon fiber textile, an epoxy resin impregnated alkaline resistant glass textile and a polyvinyl alcohol fiber textile. From these validation tests, key figures that allow for a ranking of new textiles in comparison to the already available textiles are inferred; The tensile strength of the textiles ranges from 880 to 2900 MPa, the alkaline strength degradation is at maximum −0.17 %/day and the tensile strength of the TRC elements ranges from 770 to 2310 MPa. The comparison of these values with those of a new textile enables a quick initial evaluation of the suitability of the new textile for the use in TRC.

Tensile Behavior of Basalt Textile Reinforced Concrete: Effect of Test Setups and Textile Ratios.

The clevis-grip tensile test is usually employed to evaluate the mechanical properties of textile reinforced concrete (TRC) composites, which is actually a bond test and is unsuitable for determining reliable design parameters. Thus, the clevis-grip tensile test needs further improvement to obtain foreseeable results concerning TRC tensile behavior. This paper presents the experimental results of twenty-one tension tests performed on basalt TRC (BTRC) thin plates with different test setups, i.e., clevis-grip and improved clevis-grip, and with different textile ratios. The influences of test setups and textile ratios on crack patterns, failure mode, and tensile stress-strain curves with characteristic parameters were analyzed in depth to judge the feasibility of the new test setup. The results indicated that with the new test setup, BTRC composites exhibited textile rupture at failure; in addition, multi-cracks occurred to the BTRC composites as the textile ratio exceeded 1.44%. In this case, the obtained results relied on textile properties, which can be considered reliable for design purposes. The modified ACK model with a textile utilization rate of 50% provided accurate predictions for the tensile stress-strain behavior of the BTRC composite derived from the improved test setup. The proposed test setup enables the adequate utilization of BTRC composite and the reliability of obtained results related to the occurrence of textile rupture; nevertheless, further work is required to better understand the key parameters affecting the textile utilization rate, such as the strength of the concrete matrix.

Experimental and Statistical Analysis of U-Shaped Polyurethane-Based Polymer Concrete under Static and Impact Loads as a Repair Material

The prolonged service life of civil engineering structures, such as buildings and highway pavement, means that they deteriorate with time, requiring frequent repair work. Polyurethane (PU) materials can effectively maintain engineering structures such as road pavement, runways, and buildings. Thus, the mechanical properties and dynamic performance of these materials for repair are essential to guarantee the safe usage of the facilities. This study investigated the strain–stress behavior and impact strength of polyurethane-based polymer concrete (PUPC) mixtures. Moreover, the tensile stress–strain behavior of rigid PU grout (PUGC) materials was evaluated. The result indicated that the U-shaped PUPC with 20% PU by weight experienced a maximum failure strain of 0.9% and 4.2% under static and dynamic loads, respectively. The average impact energy of PUPC was 3825% higher than that of normal concrete. According to PUGC’s mixing ratios, the average elastic modulus revealed an increasing trend, whereas ultimate strength, yield strain, yield stress, and failure stress showed a decreasing trend. Weibull distribution results showed that the probabilistic distribution of the impact strength followed the two-parameter Weibull distribution.

Micro-structural and mechanical properties of PVA fiber reinforced engineered cementitious composite incorporating natural and artificial pozzolanic materials under different temperatures

• The pozzolans' contents significantly affect the tensile strain capacity of the ECC. • Using fly ash, GGBS and zeolite can improve tensile behavior of the ECC. • The GGBS based ECC has better tensile stress–strain behavior. • At the temperatures above 50 °C, the mechanical properties of the ECC decrease. • ANN and MLR can predict the mechanical properties of the ECC with high accuracy. Engineered cementitious composites (ECC), which have high toughness and tensile ductility, as well as multiple fine cracking, satisfy the high safety and durability criteria in the development of sustainable infrastructures. The effect of different temperatures on the mechanical characteristics of polyvinyl alcohol (PVA) reinforced ECC (PVA-ECC) was examined in this work. A study was conducted to compare the modulus of elasticity, tensile strength, and compressive strength of samples containing various dosages of three available pozzolans: zeolites (ZE), fly ash (FA), and ground granulated blast furnace slag (GGBS), as well as silica fume (SF). Scanning electron microscopy was used to examine the microstructure of PVA-ECC samples subjected to various high temperatures (SEM). For 1 h, all specimens were exposed to temperatures of 150, 100, 50, and 20 °C. The experimental findings revealed that when the temperature rises to 50°, all three mechanical parameters, modulus of elasticity, tensile strength, and compressive strength, increase, then drop. The study of the microstructure of PVA-ECC reveals a basic explanation for the loss of macro mechanical characteristics. Finally, using ANOVA analysis, the relationship between independent parameters such as the age of the sample (AS), temperature (T), and water to pozzolan materials (W/P), and dependent parameters (i.e., compressive strength, tensile strength, and modulus of elasticity) was evaluated, and the multivariate linear regression (MLR) and the artificial neural network (ANN) were shown to be useful for modeling.

Study of Micro structural behaviour (MSB) in geopolymer concrete (GPC) and material properties by using waste materials

In economic growth, development of infrastructure plays a major role in the country’s. This study has overcome that to improve and nature of built in under environmentally. To overcome the problems, geopolymer concrete has been introduced which has the potential to completely eliminate conventional concrete. This study efforts on the development of light weight geo-polymer concrete and the results were related with the control mix. In this study, geopolymer concrete with Ground Granulated Blast Furnace Slag (GGBS-binder), manufactured sand (M−sand−fine aggregate), coconut shell and crushed granite (coarse aggregate) were used to produce Geopolymer Coconut Shell Concrete (GPCSC) and Geopolymer Conventional Concrete (GPCC) control mix. A introductory study was passed out for the range of a mix proportion over trial mixes. Provisional mixes were set in two mixes were used to study the possessions of geopolymer concrete GPCSC (1:3.56:1.07) and GPCC (1:5.17:4.65) with an alkaline/binder ratio of 0.75. An alkaline activator was equipped by uniting sodium silicate (Na2O, 15 %; SiO2, 28 %; and water, 57 % by mass: Na2SiO3) and sodium hydroxide (NaOH) solution with 10 Molarity. Micro structural analyses (X-ray diffraction analysis, transform infrared spectroscopy analysis, thermo-gravimetric analysis, and scanning electron-microscopy coupled with energy dispersive spectroscopy analysis) were done on the material. The mechanical behaviour of geopolymer concrete on compressive strength, split tensile strength, flexural strength, bond strength and stress strain behaviour are studied. The flexural and shear behaviour of GPCSC and GPCC were compared with the prediction equations based on stress block diagram and strain compatibility method. The long-term durability test was done on days 3, 7, 28, 56, 90, and 180 days. The durability characteristics of both GPCSC and GPCC were analysed.

Surface Damage Coupling Mechanism of Plain Weave Art Ceramic Matrix Composites

In order to solve the problem of the surface damage coupling mechanism of ceramic matrix composites, a method oriented to the damage coupling mechanism of the plain weave art ceramic matrix is proposed by the author. First, the author uses the composite material prepared by a chemical vapor infiltration process as the research object, and the damage mechanical behavior of materials under simple and complex plane stress states is studied. Second, the calculation of the mechanical property parameters of the material components and the research on the mechanical behavior of the material in-plane shear mesodamage are studied; Finally, the research on the damage coupling effect of materials under complex stress state is conducted, as well as the decoupling test research of the damage coupling effect. It is demonstrated that based on 0 and 45° off-axis tensile stress-strain behavior, a prediction model of off-axis tensile stress-strain behavior of the material was established, and the prediction results were in good agreement with the experimental results.