Strength Properties Research Articles

Predictions of sheet molding compound composite structures using probabilistic finite element simulations with bimodal Weibull strength distributions

Due to the large scatters in Sheet Molding Compound (SMC) mechanical properties, the uncertainty in the prediction of mechanical responses of SMC composite structures is significantly high as compared to that for continuous fiber composite structures. Another challenge is the size effect resulting from the scatter in mechanical strengths, i.e., the measured material flexural strength is much higher than its tensile strength. As a result, classical approaches that rely on the mean tensile strength can substantially underpredict the flexural responses in Finite Element Analysis (FEA). This work investigates the use of a material model with bimodal Weibull distributions for its strength properties in Probabilistic FE (PFE) simulations. A Random Search-based optimization procedure was developed to obtain model parameters which are difficult to determine. The material model was verified by PFE simulations of standard experiments, and then examined in simulations of open-hole tension and disk bending tests.

3D reinforcement synergistic effect of embedded nickel‐foam skeleton of polyurethane based on x‐ray CT images: Experimental and finite element analysis

AbstractMonotonic shear tests were performed on Nickel Foam (NF)/Polyurethane (PU) and the results indicated that NF/PU was much greater than the sum of the individual phases in terms of strength and stiffness. Cyclic shear tests were carried out and it was found that shear evolution processes and failure modes of the composite were completely different from the individual phases and the damping properties were greatly improved. Revealing the synergistic mechanism of the 3D continuous metal skeleton on the PU is the key issue to explain the above phenomena. The geometric topology of NF was reproduced using CT technology and a fine‐scale finite element model was established. The mechanical behavior between NF and PU was investigated at the meso‐mechanical scale. The results show that the NF skeleton significantly improves the strength and damping properties of the PU. During cyclic shear, the effects of displacement and temperature on the mechanical and damping properties of the PU are significant. In comparison, the NF skeleton reduces the temperature sensitivity. Based on the analysis of experimental and FEA results, the monotonic and cyclic constitutive models of NF/PU were established. The shear constitutive model under the new loading/unloading criterion has good fitting accuracy and high reliability.Highlights NF/PU properties were investigated by experimental and finite element methods. NF skeleton improves PU performance through the synergistic effect. Synergistic effects were revealed by CT and finite element methods. The R‐O model can fit the shear constitutive model of NF/PU.

A novel green approach for reactive printing of cotton/cellulosic regenerated blended fabrics using trisodium nitrilotriacetate

Owing to their comfort, handle, and aesthetic characteristics, cotton fabrics will always be the first and primary choice for clothing and apparel. In recent years, regenerated cellulosic fabrics like bamboo, Tencel, and modal fabrics have had many natural advantages. Fabrics based on blending cotton fibres with regenerated cellulosic fibres are considered promising products in textile industry sectors. Use of urea poses ecological problems associated with the high nitrogen content of the printing effluent. Therefore, urea reduction or elimination in reactive dye print pastes is of ecological interest. We report the use of trisodium nitrilotriacetate as a complete substitution of urea and alkali in the conventional reactive printing of cotton/cellulosic regenerated blended fabrics. CI Reactive Black 5 was selected for the present study. Three different print pastes containing urea/alkali, trisodium nitrilotriacetate/alkali and trisodium nitrilotriacetate without alkali were thoroughly investigated. Different factors that may affect the printability of cotton/cellulosic regenerated blended fabrics, such as the concentrations of dye, trisodium nitrilotriacetate, urea, absence or presence of alkali and steaming time in the prints obtained, were evaluated concerning colour strength, dye fixation, dye penetration, levelling, colure, and fastness properties. All printed fabrics using three print pastes obtained excellent to good fastness. The results proved the viability of using TNA as an environmentally friendly approach for urea/alkali-free printing of cellulosics with reactive dyes.

Investigation of Tannic Acid Crosslinked PVA/PEI-Based Hydrogels as Potential Wound Dressings with Self-Healing and High Antibacterial Properties

This study developed hydrogels containing different ratios of TA using polyvinyl alcohol (PVA) and polyethyleneimine (PEI) polymers crosslinked with tannic acid (TA) for the treatment of burn wounds. Various tests, such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), swelling, moisture retention, contact angle, tensile strength, the scratch test, antibacterial activity and the in vitro drug-release test, were applied to characterize the developed hydrogels. Additionally, the hydrogels were examined for cytotoxic properties and cell viability with the WST-1 test. TA improved both the self-healing properties of the hydrogels and showed antibacterial activity, while the added gentamicin (GEN) further increased the antibacterial activities of the hydrogels. The hydrogels exhibited good hydrophilic properties and high swelling capacity, moisture retention, and excellent antibacterial activity, especially to S. aureus. In addition, the swelling and drug-release kinetics of hydrogels were investigated, and while swelling of hydrogels obeyed the pseudo-second-order modeling, the drug release occurred in a diffusion-controlled manner according to the Higuchi and Korsmeyer–Peppas models. These results show that PVA/PEI-based hydrogels have promising potential for wound dressings with increased mechanical strength, swelling, moisture retention, self-healing, and antibacterial properties.

Synthesis of a gallic acid-based self-healing waterborne polyurethane with a thermo-responsive dynamic phenol-carbamate network for enhanced mechanical strength, antimicrobial activity, and shape memory properties

To expedite the advancement of multifunctional next-generation smart materials, it is imperative to create polymers derived from renewable, green bio-based resources. This paper presents a direct synthesis of thermo-responsive aqueous polyurethanes by combining gallic acid (GA) with isocyanate groups to form a dynamic phenol-carbamate crosslinked network and the incorporation of the metal-organic framework Cu-MOF-2 for synergistic effects. The resulting GA-based polyurethane (MOF-GWPU) exhibits excellent thermal stability and mechanical properties, achieving an ideal balance between mechanical strength and self-healing efficiency. The MOF-GWPU film demonstrates strong antimicrobial efficacy against Escherichia coli and Staphylococcus aureus, highlighting its exceptional antibacterial performance. The thermo-responsive dynamic covalent bonds enable the MOF-GWPU film to rapidly revert from a temporary shape back to its original form. Post-processing experiments further indicate that the crosslinked GA-PU polymer can be efficiently recycled through solution casting and hot-pressing techniques. This design offers a novel approach and valuable insights for advancing the development of multifunctional smart polymers derived from bio-based resources.

The preparation and construction of biomimetic mineralization compatible interface of wood fiber/foamed magnesium oxychloride lightweight composites

The purpose of this study is to improve the application performance of foamed magnesium oxychloride cement (FMOC) and solve the problem of poor interfacial compatibility between the organic-inorganic interface of traditional inorganic composite materials. Inspired by the adhesion mechanism of barnacles to inorganic substrates through amyloid nanofibers and phosphoprotein, a simple green method was proposed to improve the strength and water resistance of the system. The FMOC composites (30×30×30 mm) were prepared by adding wood flour (WF) and phytic acid (PA) to the mixture of magnesium oxide and magnesium chloride. The influences of WF and PA on the compressive strength, composition, microstructure, pore structure, water resistance and flame retardant properties of FMOC were investigated. WF was used as a skeleton structure to induce cement particle aggregation, the PA molecule was used as a connecting bridge to activate the fiber skeleton to increase the active sites, and promote crystal nucleation and aggregation through hydrogen and ionic bond interactions to construct the biomimetic mineralized structure. The results show that the introduction of PA improves the compressive strength and water resistance of the FMOC/WF/PA composite system. When the PA addition amount is 0.8 %, the compressive strength of FMOC/WF/PA-0.8 % composites reached 6.64 MPa, which was 3 times compared to the FMOC composites. The softening coefficient and water absorption of the obtained FMOC/WF/PA-0.8 % composites were 0.81 and 13.84 %, respectively, which were superior to FMOC composites and presented better behavior in water resistance. Meanwhile, the modified composites have more stable pore structure and flame retardant properties, thus these green FMOC/WF/PA composites displayed potential application value in building energy conservation, aerospace and other fields.

Predicting the Effects of Cryogenic Treatment and Impact-Oscillatory Loading on Changes in the Strength Properties of Stainless Steels

Abstract New experimental results concerning the strength properties of stainless steels are analyzed. In particular, the strength properties of steels were improved at room temperature using the preliminary impact-oscillatory loading (IOL) in liquid nitrogen. Mechanical tests performed on stainless steel 12Kh18N10T have found the IOL conditions (deformation of the material during pulse loading—εimp = 9.69%), under which the ultimate strength of steel increases by 32.2% compared to the initial state under subsequent static tensioning. Metallographic analysis of the deformed steel revealed twinning in the microstructure. This accounts for a significant increase in ultimate strength under subsequent static tensioning. A method for estimating the ultimate strength of stainless steels of different chemical compositions by changing the percentage of the main chemical elements is proposed. To test this technique, stainless steel 12Kh18N9 was chosen. Similar studies using this steel at εimp = 9.5% in liquid nitrogen followed by static tensioning at room temperature have confirmed the effectiveness of the proposed approach.

Synthesis of Few Layers Graphene Sheets from Graphite Rod via Electrochemical Exfoliation

Graphene has many excellent properties in mechanical strength, electrical conductivity, optical transparency and thermal conductivity. The basic unit of graphene is made of hexagonal ring of carbon shape. The production of graphene in large amounts can be done using conventional ways such as chemical vapour deposition (CVD). However, the cost production is very high due to high reaction temperature. Therefore, electrochemical exfoliation could become a promising method in future because of its simple, low cost and large-scale production. Electrochemical method is performed in the manner by connecting the graphite rod to the positive terminal (anode) while the copper sheet is connected to the negative terminal (cathode) and both of were immersed into electrolyte with a distance between them. Then, due to the potential difference, the exfoliation of graphite into graphene sheets occurs. X-Ray Diffraction revealed that high amount of exfoliated graphene sheets was synthesized successfully where the peak was seen at approximately 26.60°. Fourier Transform Infrared confirmed the synthesized of graphene oxide (GO) sheets (by using H2SO4 as electrolyte) shows the higher intensity of O-H band because of strongest oxidation behaviour of H2SO4 acid among all electrolytes used in experiment. Besides. SEM images show that the morphologies of the exfoliated graphene sheets have stacked, flaky-like, wrinkled and crumpled structures.

Dynamic and quasi static stiffness characterization of a lamination stack of an electric motor

The development of electric motors for automotive applications requires precise material models to simulate structural strength and NVH (Noise, Vibration, and Harshness) properties. Modeling the behavior of lamination stacks, composed of stacked steel plates, presents significant challenges. This study conducted dynamic and quasi-static experiments at various preload levels on an unmodified automotive lamination stack. Significant discrepancies were identified between stiffness values obtained from static and dynamic measurements. Consequently, using dynamically obtained stiffness values in static models, and vice versa, leads to inaccuracies and should be avoided. These results enhance the precision and efficiency of simulations used in the design and optimization of electric motors.

Enhancing mechanical and corrosion properties of Al-Zn-Mg-Cu alloy through electropulsing and aging alternate treatment

The contradiction between mechanical and corrosion properties restricts the further research and application of Al-Zn-Mg-Cu alloy. Studies report a new technique, electropulsing and aging alternate treatment (EPAAT), including twice electropulsing and aging treatment, to solve this contradiction by precisely controlling the intragranular precipitates and grain boundary precipitates (GBPs). The results show that the grain boundary precipitates (GBPs, η) are discontinuous and the intragranular precipitates (η’) are not coarsened after EPAAT. The precise regulation of precipitated phase by EPAAT can be attributed the differing effect of electropulsing current on the GBPs and the intragranular precipitates. Utilize electropulsing primary treatment to obtain the supersaturated solid solution. Following natural aging, the small continuous phases at the grain boundary and the GP zones within the grain were precipitated again. The small continuous GPBs of the sample diffuse along the grain boundaries and become discontinuously distributed, while the GP zones within the grain dissolve with under the electropulsing secondary treatment. After artificial aging, the intragranular phase is fully precipitated, yet the GBPs remain unchanged, thereby achieving phase regulation. Consequently, the icorr of Al-Zn-Mg-Cu alloy decreases from 28 to 5.87 μA/cm2 and the tensile strength increases from 511 MPa to 524 MPa. The EPAAT technology realizes the accurate treatment of Al-Zn-Mg-Cu alloys and provides a new solution for improving strength and corrosion properties.

Effect of Proteins on the Vulcanized Natural Rubber Crosslinking Network Structure and Mechanical Properties.

Proteins are important factors affecting the properties of natural rubber. Therefore, investigating the effect of free and bonded proteins on the structure and mechanical properties of the vulcanized crosslinking network of natural rubber would provide a theoretical basis for the production of high mechanical resistance natural rubber. Herein, natural rubbers with different protein contents and types were prepared by high-speed centrifugation. And, the effects on their network structure, vulcanization, tensile strength, tearing strength and dynamic mechanical properties were investigated. The results showed that the reduction in protein content led to the decrement in the entanglement networks, crosslinking density and tensile and tear strengths of the vulcanized natural rubber. Moreover, the bonded proteins had an obvious influence on the vulcanization process, while free proteins played an important role in the crosslink densities. These results reveal that both bonded and free proteins are involved in the vulcanization process and the construction of the vulcanized crosslinking network structure of natural rubber, which enhances the mechanical properties such as the modulus and tensile strength of vulcanized natural rubber.

2D Embedded Ultrawide Bandgap Devices for Extreme Environment Applications.

Ultrawide bandgap semiconductors such as AlGaN, AlN, diamond, and β-Ga2O3 have significantly enhanced the functionality of electronic and optoelectronic devices, particularly in harsh environment conditions. However, some of these materials face challenges such as low thermal conductivity, limited P-type conductivity, and scalability issues, which can hinder device performance under extreme conditions like high temperature and irradiation. In this review paper, we explore the integration of various two-dimensional materials (2DMs) to address these challenges. These materials offer excellent properties such as high thermal conductivity, mechanical strength, and electrical properties. Notably, graphene, hexagonal boron nitride, transition metal dichalcogenides, 2D and quasi-2D Ga2O3, TeO2, and others are investigated for their potential in improving ultrawide bandgap semiconductor-based devices. We highlight the significant improvement observed in the device performance after the incorporation of 2D materials. By leveraging the properties of these materials, ultrawide bandgap semiconductor devices demonstrate enhanced functionality and resilience in harsh environmental conditions. This review provides valuable insights into the role of 2D materials in advancing the field of ultrawide bandgap semiconductors and highlights opportunities for further research and development in this area.

Nanocellulose‐polypropylene composites with novel antimicrobial complex salt

AbstractPolypropylene composites with different contents of zinc‐ammonium salts (3, 5 and 7 wt%) and nanocellulose (1 wt%) after enzymatic bioconversion were characterized by structural, dispersion‐morphological, thermal, antimicrobial and mechanical analysis. It was shown that the use of a newly synthesized salt significantly affected the formation of the supermolecular structure of the polymer matrix and increased the nucleation activity, thermostability and flexibility of the composite materials. Moreover, the addition of the inorganic filler allowed to obtain composites with very good antimicrobial properties against Staphylococcus aureus, Escherichia coli and Candida albicans. An interesting relationship between the degree of filler dispersion in the polymer matrix and the formation of polymorphic varieties was elucidated in the study, which contributes to the improvement of final performance characteristics of composite materials. It is noteworthy that a hybrid filler in the form of nanometric cellulose and a biocidal additive containing zinc‐ammonium complex salt was used for the first time. Research has shown that such polymer composites can find application during the manufacture of smart packaging materials with enhanced barrier properties against oxygen and water vapor as well as improved biocidal characteristics, which will notably extend food storage time. At the same time, the presented process of obtaining the innovative composite materials is an excellent example of sustainable technologies for the design of antimicrobial treatments, while guaranteeing the possibility of further processing of these composite materials through material recycling.Highlights Zinc‐ammonium complex with antimicrobial properties was obtained The strength properties and thermal stability of the composites were improved Degree of filler dispersion in polymer affects formation of polymorphic varieties The composites can be applied in the production of smart packaging materials

Mechanical Properties of Spunlace Non-Wovens with a Porous Structure

The paper describes the influence of the drum system construction of two modern carding machines on the porous structure of spunlace non-wovens composed of polyester and viscose. The non-woven fabric structure, including the number and size of the pores, determines the tensile strength of the composites obtained. The spunlace non-wovens were subjected to tensile strength tests in the machine, and cross-directions and microscopic observations of their structure were made. The results of the experiments were used to determine the relationship between the strength of the material and the porosity of its structure. This knowledge was used to prepare recommendations for the manufacturer of wet wipes in order to enable the selection of a carding machine for the mass production of final products with strength properties that meet market requirements and satisfy the end customer.

The Abrasive Water Jet Cutting Process of Carbon-Fiber-Reinforced Polylactic Acid Samples Obtained by Additive Manufacturing: A Comparative Analysis

Carbon-fiber-reinforced polymer (CFRP) composites are widely used across industries due to their enhanced strength and stiffness properties. Fused deposition modeling (FDM) enables the cost-effective production of polymer samples, such as carbon-fiber-reinforced PLA (CFR-PLA). However, CFRP’s hardness and anisotropic nature present significant challenges in conventional machining, including rapid tool wear and thermal sensitivity. Consequently, abrasive water jet machining (AWJM) has proven to be an effective alternative for machining CFRP materials, offering benefits such as reduced tool wear, minimized thermal damage, and improved cutting quality. This study focuses on a comparative analysis of the effects of AWJM parameters on PLA and CFR-PLA samples, specifically to evaluate the influence of carbon fiber reinforcement on machining performance. The findings highlight the critical role of reinforcements in machining behavior. The results suggest that optimizing cutting parameters significantly reduces taper formation and improves machining accuracy. In particular, adjustments to process parameters resulted in lower taper angles and reduced surface roughness in the cutting zones of the CFR-PLA samples.

Gypsum Binder With Increased Water Resistance Derived From Membrane Water Desalination Waste

ABSTRACTA method has been developed for separating a mixture of calcium, magnesium and sodium sulfates obtained through the interaction of sulfuric acid and waste from the water purification process generated by using membrane filters. The primary goal of this method is to extract gypsum and produce gypsum‐based binders. Patterns were identified regarding how various types, ratio and quantities of additives: blast furnace slag, granite screenings, portland cement, electric steel smelting slag affect the water‐gypsum ratio, strength properties, and water resistance of high‐strength gypsum binders. It was found that adding a single‐component additive specifically to enhance water resistance does not significantly impact these properties. Complex additives have been developed based on Portland cement, granulated blast furnace slag, electric furnace slag, expanded clay dust, and granite screenings of various fractions. These additives are designed to maximize the water resistance of high‐strength gypsum binder based on synthetic calcium sulfate dihydrate. As a result, the water resistance coefficient increased from 0.45 to 0.52. Additionally, a technological block diagram of the process has been proposed.

Study on properties and CO2 emission of self-pulverizing calcium sulfoaluminate (SPCSA) after carbonization curing

The extensive use of Portland cement (OPC) has resulted in a steady rise in CO2 emissions from the construction industry, posing a significant climate threat. While adopting low-carbon cement enriched with belite minerals holds promise for substantial CO2 emission reduction in the cement industry, the limited early hydration activity of C2S constrains its engineering applications. Carbon capture, storage, and utilization (CCUS) technology, capable of rapidly developing the strength of C2S, opens up a new avenue for utilizing low-carbon cement. This study evaluated the properties of self-powdering calcium sulfoaluminate (SPCSA) cements with different C2S contents, and the carbon emissions during production and application were analyzed. The samples' carbonation area, compressive strength, and capillary water absorption properties were tested. The carbonation products and pore structures were also characterized using XRD, TGA, SEM, and Low-NMR. The results show that when the molar ratio of C4A3S̅ to C2S is 1:12 (S̅12), the compressive strength and CO2 sequestration of SPCSA are 69.78 MPa and 0.15 g/g, respectively. When CCUS technology is adopted, the CO2 emission during the production and application of SPCSA is 585.78 kg/t, much lower than that of OPC of 878.28 kg/t. This is significant as a reference for realizing carbon neutrality in the cement industry.

Silicomanganese fume-based alkali-activated mortar: experimental, statistical, and environmental impact studies.

This paper evaluates the flowability and strength properties of alkali-activated mortar produced using silicomanganese fume (SiMnF) as the sole binder, combined with alkaline activators and sand, cured at room temperature (23 ± 1 °C). A total of 18 mixes were prepared by varying binder content (370, 470, and 570 kg/m3), alkaline activator content (33, 43, and 53% of binder by weight), and NaOH concentration (8 M and 12 M). The SiMnF-based alkali-activated pastes were characterized using SEM, XRD, and FTIR techniques to study morphology, mineral composition, and functional groups, respectively. Statistical modeling, including analysis of variance (ANOVA) and response surface method (RSM), was performed to optimize the mixes, and a life cycle assessment was conducted to evaluate the environmental impact of the developed SiMnF-based alkali-activated mortars (SiMnF-AAM). The experimental results showed that an optimal mix design with 470kg/m3 SiMnF, 43% alkaline activator content, and NaOH concentrations of 8M and 12M achieved the best balance of flow and strength. XRD and FTIR analyses confirmed that Nchwaningite was the primary reaction product, with secondary phases including magnetite, manganese ferrite, and potassium feldspar, influenced by alkali concentration. The SiMnF-based mixtures had a significantly lower CO₂ footprint (0.08kg CO₂/kg) compared to the cement-based mix, with alkali activators being the primary contributors to emissions. The developed SiMnF-AAM mixes, cured at room temperature, exhibited improved workability, mechanical properties, and reduced environmental impact, making them adaptive to real-life applications.

Application of Kolmogorov-Sinai's Metric Entropy for the Analysis of Mechanical Properties in the Bending Test of Epoxy-Rubber-Glass Composites.

The article presents an analysis of the results obtained during the three-point bending test for seven variants of epoxy rubber-glass composites manufactured according to innovative technology. Different contents of rubber recyclate (3, 5, and 7%) and different methods of distribution of the recyclate in the composite structure (1, 2, and 3 layers with a constant share of 5% of the recyclate) were used in the tested materials. To determine the stress values at which critical failures of the tested materials are initiated in the bending test, an analysis was carried out using the Kolmogorov-Sinai (EK-S) metric entropy calculations. The analysis results showed that for each of the above-mentioned variants of the tested epoxy-glass composites, the onset of critical changes occurring in the material structure occurs below the recorded values of the flexural strength Rmg. The decrease in the RmgK-S value in relation to Rmg is different for different material variants and depends mainly on the % content of rubber recyclate and the amount and method of decomposition of rubber recyclate in the layers of the analyzed materials. The research showed that the introduction of rubber recyclate into the composition of composites has a positive effect on their strength properties. This process allows for the efficient use of hard to degrade waste and opens up the possibility of using the newly developed materials in many industrial sectors.

Compressive behavior of additively manufactured lightweight structures: Infill density optimization based on energy absorption diagrams

The use of 3D-printed components as load-bearing structures is widely studied, while their use as energy absorbers constitutes a gap in the additive manufacturing (AM) field. Most of the reported works address the compressive behavior of AM parts up to low strains (<15%), thus omitting many important properties. Therefore, this paper presents the compression characterization of Polylactic Acid (PLA) samples with different infill densities-IDs (10–100% range, with a step of 10%) fabricated by material extrusion (MEX) AM process. The physical (dimensional accuracy, printing time and sample mass) and mechanical (elastic, strength, strain and energy absorption) properties are determined and discussed in detail, along with the failure mechanisms that occur in the samples. Moreover, an ID optimization is performed based on the energy absorption diagrams (EAD), a unique approach in the AM field. The highest values of compressive strength (81 MPa) and modulus (1306.6 MPa) are found for 90%-ID, over 2.2% higher than those obtained for 100%-ID. On the other hand, based on three different approaches, EAD identified 30%-ID as optimal. The 30%-ID samples absorb the largest amount of energy (12 MJ/m3) at the lowest (ideal) peak stress value (23.57 MPa), which is 69.1% lower than that for 100%-ID. At low IDs (<30%), the samples exhibit a brittle behavior, changing to a ductile one with the increase of ID (≥40%). The MEX-printed PLA samples show a dimensional relative error below 0.15%, and the optimization process reduces the amount of filament material by 54.3% and the printing time by 42.7%.