Strength Of Materials Research Articles

Hysteresis Behavior of Reinforced Concrete Column Retrofitted and Repaired with Carbon Fiber Sheet

Structures experience damage and deterioration over their life cycle. The recent increase in interest in sustainable development of cities is re-evaluating the long-term use of structures. Therefore, researches on the retrofitting method for existing structures is receiving high attention again. However, there are very few cases where the direct comparison between the repair and retrofitting effects of structures has been experimentally verified. In this study, retrofitting methods and repair methods with carbon fiber sheets for reinforced concrete columns under shear failure were investigated. 10 reinforced concrete columns were tested under reversed cyclic loading. As a result of the experiment, it was found that, when reinforced with CFS strips, the increase in the width of the strip serves to enhance the strength and ductility of the reinforced member by providing confinement against shear cracks occurring in concrete. It was confirmed that as the number of overlaps of CFS increased, a greater strength-enhancing effect and ductility-enhancing effect appeared. However, the two-way reinforcement of CFS did not show a great effect in improving strength and ductility. As a result of evaluating the repair performance of damaged members using CFS, it was found that the strength and ductility of the repaired specimen exceeded the original strength and ductility of the base material as well as the strength and ductility of the reinforced specimen.

Phase-field modeling of interfacial fracture in quasicrystal composites

Quasicrystals (QCs) have been used as a particle reinforcement phase in polymer or metal matrix composites to enhance the material strength, hardness and wear resistance while maintaining the lightweight advantages of the composites. In this paper, a phase-field fracture model (PFM) is proposed to predict crack propagation and interfacial debonding in QC composites. The phase-field and interface-field variables are introduced to regularize the cracks and interfaces in the composites, respectively. An equivalent critical energy release rate is introduced to characterize the influence of the interface on crack propagation. The present model is numerically implemented in Comsol Multiphysics based on the Weak Form PDE module. Several numerical examples are simulated to demonstrate the ability of the proposed model to predict crack propagation and interfacial failure of QC composites and to analyze the influence of QC reinforcement phase on fracture behaviors of QC composites. Numerical results indicate that the interface significantly influences the crack propagation paths, and the phason elastic field has a remarkable influence on the peak force and failure displacement in the fracture test of QC composites. The developed phase-field model and numeral implementation approach provide a convenient tool for predicting interfacial failure and assessing the safety of QC composites in engineering.

Determination and Sensitivity Analysis of Target Flaw Sizes for Performance Demonstration of Cast Austenitic Stainless Steel Pipe by Probabilistic Fracture Mechanics

Abstract The material of primary coolant pipe of nuclear power plants is cast austenitic stainless steel (CASS), which has a coarse crystal structure and its anisotropy causes low permeability of ultrasonic waves and low detectability. Also, the material strength and fracture toughness of CASS are affected by thermal aging depending on ferrite content, chemical compositions and casting process. The ASME Section XI Code Case N-838 provides the target flaw sizes for performance demonstration (PD) examination system of ultrasonic testing (UT) based on probabilistic fracture mechanics (PFM) analysis incorporated a thermal aging model. In this study, the target flaw sizes for Japanese pressurized water reactor (PWR) plants were investigated by using the PFM analysis code “PREFACE.” Thermal aging prediction models for tensile strength and fracture toughness of CASS were incorporated into the PREFACE Code depending on not only ferrite content and chemical compositions but also the casting process, centrifugal casting, or static casting. Those parameters were input as probabilistic variables, which were based on the material database from the Japanese PWR plants. The PFM analysis revealed that static CASS pipes have smaller target flaw sizes than centrifugal CASS pipes and the obtained target flaw sizes were very close to those in ASME Code Case N-838.

Effect of Elevated Temperature on Compressive Strength of MICCP and EICCP Biocemented Mortar.

Recently biocementation has got attention of many researchers worldwide as one of the most potent techniques for sustainable construction. Several studies have been carried out worldwide on biocementation by urea hydrolysis. Biocementation by bacterially induced calcium carbonate precipitation by different bacterial species has been among the most widely researched areas in this field. Biocementation has proved efficient in enhancing the strength and durability of cement-based materials. However, no significant work has been carried out to determine the performance of biocemented specimens at elevated temperatures. This study primarily focuses on the effects of high temperatures (300, 450, and 600°C) on the compressive strength of two types of biocemented specimens prepared by using ureolytic bacteria and rich in urease watermelon seeds. The motive behind testing these two types is to know how the enzyme induced or microbially induced react to temperature elevation. Also, the effect of different cooling techniques (viz., natural cooling, water spray cooling and fire extinguishing foam spray cooling) were studied. These cooling techniques were selected so as to check which cooling technique should be preferred in case of fire situation in a cement-based structure. Results show that biocemented specimens can perform very good up to the temperature 300°C as compared to control specimens in terms of compressive strength. At 450°C temperature, there is no significant difference in compressive strengths of control and biocemented specimens. When the specimens were subjected to 600°C, biocemented specimens showed lower strength than control specimens at the same temperature due to denser microstructures. Thus, biocemented cement mortar should not be used in reactors, muffles and ovens where temperature would go above 450°C.

Microstructural Evolution and Properties of ZrB2‐Reinforced AA6111 Aluminum Matrix Composites Subjected to Double‐Sided Friction Stir Processing

Single‐sided friction stir processing (S‐FSP), owing to its intrinsic structural characteristics, including the advancing side and the retreating side and the nonuniformity of attributes, restricts the enhancement of the strength of aluminum composite materials. Herein, the preparation of AA6111/ZrB2 aluminum matrix composites, 4 mm in thickness, via an in situ autogenous casting process is presented. The composites undergo double‐sided FSP (D‐FSP) with varying parameters, utilizing an orthogonal test method. In these findings, it is indicated that the mean grain size of the nugget zone (NZ) post D‐FSP is reduced from 5.56 μm in S‐FSP to 4.65 μm, the percentage of low‐angle grain boundaries diminishes from 31.4% to 26.9%, and the recrystallized structure escalates from 49.7% to 65.2%. At a rotational speed of 1000 r min−1 and a processing speed of 40 mm min−1, the average hardness of the NZ of D‐FSP is augmented by 6.3% relative to S‐FSP; the ultimate tensile strength and elongation of the material are enhanced by 1.6% and 31.7%, respectively, compared to S‐FSP, while the product of strength and elongation is increased by 33.2%.

Superstrong Lightweight Aerogel with Supercontinuous Layer by Surface Reaction.

Breaking the thermal, mechanical and lightweight performance limit of aerogels has pivotal significance on thermal protection, new energy utilization, high-temperature catalysis, structural engineering, and physics, but is severely limited by the serious discrete characteristics between grain boundary and nano-units interfaces. Herein, a thermodynamically driven surface reaction and confined crystallization process is reported to synthesize a centimeter-scale supercontinuous ZrO2 nanolayer on ZrO2-SiO2 fiber aerogel surface, which significantly improved its thermal and mechanical properties with density almost unchanged (≈26 mgcm-3). Systematic structure analysis confirms that the supercontinuous layer achieves a close connection between grains and fibers through Zr─O─Si bonds. The as-prepared aerogel exhibits record-breaking specific strength (≈84615 Nmkg-1, can support up to ≈227272 times aerogel mass) and dynamic impact resistance (withstanding impacts up to 500 times aerogel mass and up to 200 cycling stability at 80% strain). Besides, its temperature resistance has also been greatly optimized (400°C enhancement, stability at 1500°C). This work will provide a new perspective for exploring the limits of lightweight, high strength, and thermal properties of solid materials.

Flexural Strength, Fatigue Behavior, and Microhardness of Three-Dimensional (3D)-Printed Resin Material for Indirect Restorations: A Systematic Review

The purpose of this systematic review was to evaluate three mechanical properties of 3D-printed resins for indirect restorations according to published scientific evidence. This systematic review was conducted according to the PRISMA statement (preferred reporting elements for systematic reviews and meta-analyses). The search was performed by two investigators, (DD) and (VB), and a third (AC) resolved disagreements. Articles were searched in four digital databases: PubMed, EBSCO, Lilacs, and Science Direct, starting on 18 February 2024. As 3D-printing technology has shown significant advances in the last 5 years, the review was conducted with a publication year range between 2019 and 2024, in English language and included in vitro articles on the mechanical properties of flexural strength, fatigue behavior, and microhardness of 3D-printed materials for temporary or definitive restorations. MeSH terms and free terms were used for the titles and abstracts of each article. Finally, the QUIN tool was used to assess the risk of bias. In the main search, 227 articles were found, of which 20 duplicates were excluded, leaving 207 articles; of these, titles and abstracts were read, and 181 that did not meet the eligibility criteria were eliminated; of the remaining 26 articles, 1 article was eliminated for not presenting quantitative results. Regarding publication bias, 6 of the 25 articles had a low risk of bias, 18 had a medium risk of bias, and 1 had a high risk of bias. It may be concluded that 3D-printed resins have lower flexural strength, fatigue behavior, and microhardness than other resin types used for the fabrication of temporary and permanent restorations. The type of 3D printer and polymerization time could be factors that significantly affect the flexural strength, fatigue behavior and microhardness of 3D-printed resins. Based on existing evidence, it should be considered that additive technology has promising future prospects for temporary and permanent dental restorations.

Enhanced Hardness and Tribological Properties of Copper-Based Steel Backing Self-Lubricating Materials with Y2O3 Micro-Doping

The copper-based steel backing material is prepared using a combination of mechanical alloying and secondary sintering methods. The effect of Y2O3 content on the microstructure, hardness, and tribological properties of the copper-based self-lubricating layer is investigated. The results demonstrate that the addition of Y2O3 enhances the strength of the copper-based self-lubricating layer. Graphite and Y2O3 act synergistically to form a three-dimensional supporting framework, thereby boosting the overall strength of the copper-based composite material and increasing its Brinell hardness by 27%. Additionally, the incorporation of Y2O3 effectively improves the tribological properties of the composite material, significantly reducing wear during the friction process and decreasing the wear rate by 77%. Under the experimental conditions, the optimal Y2O3 content is determined to be 1 wt%.

Deamination mechanism of modified magnesium slag using wet aging and its performance evolution as backfill material.

The purpose of this study is to solve the problem of ammonia (NH3) release when modified magnesium slag (MMS) is used as coal mine backfill cementitious material, and to explore its chemical mechanism and put forward effective solutions. Uniaxial compressive strengths (UCS) hydration kinetics, scanning electron microscope (SEM), and thermogravimetric analysis-derivative thermogravimetry (TG-DTG), X-ray diffractometer (XRD) and other testing methods were used to study the evolution of the properties of MMS-based backfill material, which provided a scientific basis for the safe utilization of MMS. First, the chemical mechanism underlying the release of NH3 from MMS was identified, and it was confirmed that Mg3N2 and Li3N are the main nitrogen sources. This conclusion is based on thermochemical theory and the Pidgeon method. Secondly, the wet aging method was proposed to reduce the NH3 release from MMS-based backfill material. In addition, a continuous on-line gas detection system was used to determine the NH3 release pattern of MMS-based cementitious material under various aging water contents. The experiment showed a significant reduction in NH3 release with a lower aging water content of 3% and a reduction ratio as high as 81.55%. As the aging water content increased, the 28-day UCS gradually decreased. However, compared to the dry aging group, it remained above 3MPa when the aging water content was below 6%. The wet aging method can significantly shorten the pre-induction, induction, and acceleration periods of MMS-based cementitious material. The microstructure of the wet aging group exhibited fewer needle-like and rod-like ettringite (AFt) crystals as well as less flocculent hydrated calcium silicate (C-S-H) gel, whereas the unhydrated group had more fly ash (FA) and pores. Considering the UCS and NH3 release performance of MMS-based cementitious material, it is recommended to adopt a 3% aging water content and control the aging period to 7 days to effectively reduce NH3 release while ensuring the material's strength, thereby meeting the application requirements for coal mine backfill cementitious material.

Structural Effects on Compressive Strength Enhancement of Cellular Concrete During the Split Hopkinson Pressure Bar Test

In recent years, a kind of novel cellular concrete, fabricated by spherical saturated superabsorbent polymers, was developed. Its compressive behavior under high strain rate loadings has been studied by split Hopkinson pressure bar equipment in previous research, which revealed an obvious strain rate effect. It has been found by many researchers that the dynamic increase factor (DIF) of compressive strength for concrete-like materials measured by SHPB includes considerable structural effects, which cannot be considered as a genuine strain rate effect. Based on the extended Drucker–Prager model in Abaqus, this paper uses numerical SHPB tests to investigate structural effects in dynamic compression for this novel cellular concrete. It is found that the increment in compressive strength caused by lateral inertia confinement decreases from 5.9 MPa for a specimen with a porosity of 10% to 2 MPa for a specimen with a porosity of 40% at a strain rate level of 70/s, while the same decreasing trend was found at other strain rate levels of 100/s and 140/s. The lateral inertia confinement effect inside the cellular concrete specimen can be divided into the elastic development stage and plastic development stage, bounded by the moment dynamic stress equilibrium is achieved. The results obtained in this research can help to obtain a better understanding of the enhancement mechanism of the compressive strength of cellular concrete.

Investigation of the influence of the loading direction on the strength of composite materials

Investigation of the influence of the loading direction on the strength of composite materials

Mechanical Properties and Constitutive Model of High-Mass-Fraction Pressed Tungsten Powder/Polytetrafluoroethylene-Based Composites

Heavy metal powders driven by explosions can enhance the near-field lethality of explosive warheads by forming a quasi-pressure field while reducing collateral damage at medium and long ranges. Incorporating polymers into high-content metal powders prevents powder sintering under explosive high pressure, enhancing dispersion uniformity and making them promising for controllable warhead applications. To describe the mechanical behavior of materials under impact loading, this paper investigates the dynamic and static mechanical properties and constitutive modeling of tungsten powder/polytetrafluoroethylene (PTFE) composites. Quasi-static compression tests and split Hopkinson pressure bar (SHPB) dynamic tests were conducted on composites with varying tungsten contents (0 wt%, 70 wt%, 80 wt%, and 90 wt%) and particle sizes (200 μm, 400 μm, and 600 μm), obtaining compressive stress–strain curves over a strain rate range of 0.001 to 3610 s−1. The compressive strength of the composites slightly decreased with increasing tungsten particle size but increased with higher tungsten content. Under quasi-static compression, the compressive strength of the composites with 70 wt% and 80 wt% tungsten was lower than that of pure PTFE. This was due to the bonding strength between the tungsten particles and the resin being weaker than the cohesion within the resin. Additionally, the random distribution of the tungsten particles in the matrix led to shear cracks propagating along the phase interfaces, reducing the compressive strength. The compressive strength of the composites with 90 wt% tungsten exceeded that of pure PTFE, as the packed arrangement of the tungsten particles increased the material strength through particle extrusion and friction during compression. Under dynamic impact, the compressive strength of the composites was higher than that of pure PTFE, primarily due to particle extrusion and friction effects. The composites exhibited significant strain rate sensitivity, with both the compressive strength and critical strain increasing quasi-linearly with the strain rate. Based on the experimental data, a damage-modified Zhu–Wang–Tang (ZWT) viscoelastic model was employed to fit the data, effectively characterizing the uniaxial compressive constitutive behavior of tungsten powder/PTFE composites.

The role of aging and various surface preparation methods in the repair of nanohybrid composites

BackgroundRepairing composite resins is a less invasive alternative to complete restoration replacement. To achieve a successful bond between the existing and newly applied composite materials, various surface preparation methods, such as sandblasting and acid etching, have been explored. The aim of the study was to evaluate the effect of different surface treatments on the repair bond strength of a universal nanohybrid composite resin restorative material before and after thermal aging, by utilizing a micro-shear bond strength (µSBS) test.MethodsFor the micro-shear bond strength test, a total of 120 cylindrical (3mmX2mm) nanohybrid resin based composite specimens were prepared. The prepared specimens were divided into three groups (n = 40/per group) based on surface treatment methods: a non-aged group, 10,000 thermal cycle aging and 50,000 thermal cycle aging. The aged and non-aged specimens were further divided into four groups according to adhesive application modes and surface pretreatment methods: 1.universal adhesive/self-etch mode, 2.aluminum oxide sandblasting + universal adhesive/self-etch mode, 3.universal adhesive/etch-and-rinse mode, 4.aluminum oxide sandblasting + universal adhesive/etch-and-rinse mode. Subsequently, 0.8mmX2mm disc shape light cure resin based composite specimens were applied with a direct placement technique on the treated surfaces of all samples for repair. µSBS test was performed using a universal testing machine at a crosshead speed of 1 mm/min. Kruskal-Wallis and Mann-Whitney tests were performed for statistical analysis.ResultsThe µSBS values of the non-aged group were higher than those of the 10,000 and 50,000 thermal cycle groups, with no significant differences within the non-aged subgroup (p > 0.05). In the aged groups, significant differences were observed between adhesive application modes and surface treatments. Specifically, the etch-and-rinse mode showed higher bond strengths than the self-etch mode after 50,000 thermal cycles (p < 0.05). Sandblasting combined with universal adhesive (self-etch mode) improved bond strength, especially in the 10,000 thermal cycle group (p < 0.05).ConclusionAging reduced the bond strength of composite resin repairs, with the etch-and-rinse mode outperforming the self-etch mode in aged specimens. Sandblasting alone did not enhance bond strength. These findings highlight the importance of considering aging and adhesive strategies to optimize repair outcomes, with further research needed on long-term durability.

Optimization Using Central Composite Design of the Response Surface Methodology for the Compressive Strength of Alkali-Activated Material from Rice Husk Ash

Alkali-activated materials are promising alternatives to cement. This study investigated the effects of the silica content, particle size, and replacement ratio of rice husk ash (RHA) on the compressive strength and the optimization of these parameters. Seventeen mixtures with different materials were tested to evaluate their compressive strengths. Three levels of particle size, silica content, and RHA replacement ratio were used. The effects of RHA characteristics on the compressive strength were investigated based on Archimedes porosity, pH, ignition loss, and X-ray diffraction. The experimental results reveal that the replacement ratio of RHA was p-values &lt; 0.002, which affected the compressive strength compared with the particle size (p-values &lt; 0.450) and silica content of the RHA (p-values &lt; 0.017). It was confirmed that the optimum values of particle size, silica content, and replacement ratio of RHA were 50 µm, 90%, and 15 wt.%, respectively. After re-testing, the compressive strength of mortar made with the optimum values was 49.8 MPa. This increase in compressive strength was also found to be closely related to the porosity, pH, and ignition loss of the paste. It was confirmed that the replacement ratio of RHA increased with decreasing porosity and pH and increasing ignition loss, which was related to the formation of calcite and C-S-H.

Zoning design of cemented sand and gravel dam materials based on DeepFit–memory gradient search–particle swarm optimization fitting optimization

Cemented sand and gravel (CSG) dams are preferred for their cost-effectiveness and adaptability. This study introduces a zoning fitting optimization design method aimed at improving material strength utilization and reducing construction costs. Using Latin sampling and reduced strength safety calculations, an implicit function relationship is established between zoning parameters and safety through an improved deep neural network (DNN). Subsequent dimensionality reduction facilitates optimization using the memory gradient search–particle swarm optimization (MGS-PSO) algorithm. The method's efficacy is demonstrated by optimizing zoning parameters for Japan's Tobetsu Dam, achieving significant improvements in safety and material use. This approach increases safety by 22% and reduces cementing dosage by 36% compared to traditional methods, underscoring its potential in enhancing dam stability and efficiency.

A study on the compressive strength of three-dimensional direct printing aligner material for specific designing of clear aligners

BackgroundThe demand for orthodontic treatment using clear aligners has been gradually increasing because of their superior esthetics compared with conventional fixed orthodontic therapy. This study aimed to evaluate and compare the compressive strength of three-dimensional direct printing aligners (3DPA) with that of conventional thermo-forming aligners (TFA) to determine their clinical applicability. In the experimental group, the 3DPA material TC-85 (TC-85 full) was used to create angular protrusions called rectangular pressure areas (RPA). A protrusion akin to the power ridge typically employed in conventional TFAs was created using glycol-modified polyethylene terephthalate (PETG; Control 1). RPA was created using the same TC-85 without filling the protrusions (TC-85 blank; Control 2). Compression cycle tests were conducted on an LTM 3 h electrodynamic testing machine (Zwick Roell, Germany), with 500 cycles and compression depths of 100, 300, 500, and 700 µm. Twenty specimens were tested for PETG, 17 for the TC-85 blank, and 19 for the TC-85 full.ResultsChanges in the compressive force were assessed based on the material and thickness. The results indicated significantly higher and broader ranges of compressive strength for specimens fabricated with the 3DPA material TC-85 compared with those fabricated using PETG. Among the TC-85 specimens, TC-85 full demonstrated the highest statistically significant compressive strength .Conclusions3DPA technology enables precise modifications in the shape and inner thickness at specific dental sites, including the creation of ridges in targeted areas, of aligners. These alterations enhance the biomechanical capability of aligners to exert selective forces necessary for desired tooth movement while reducing the number of attachments, thereby demonstrating the clinical potential of 3D-printed aligners in orthodontic treatment.

Associations between bone material strength index and FRAX scores.

Impact microindentation (IMI) measures bone material strength index (BMSi) in vivo. However, its ability to predict fractures is still uncertain. This study aimed to determine the association between BMSi and 10year fracture probability, as calculated by the FRAX algorithm. BMSi was measured using the OsteoProbe in 388 men (ages 40-90yr) from the Geelong Osteoporosis Study. The probabilities for a major osteoporotic fracture (MOF) and hip fracture (HF) were calculated using the Australian FRAX tool. Hip (HF) and major osteoporotic (MOF) fracture probabilities were computed with and without the inclusion of femoral neck bone mineral density (BMD). For each participant, four 10year probability scores were therefore generated: (i) HF-FRAXnoBMD; (ii) HF-FRAXBMD; (iii) MOF-FRAXnoBMD; (iv) MOF-FRAXBMD. BMSi was negatively correlated with age (r = -0.114, p = 0.025), no associations were detected between BMSi and femoral neck BMD (r = + 0.035, p = 0.507). BMSi was negatively correlated with HF-FRAXnoBMD (r = -0.135, p = 0.008) and MOF-FRAXnoBMD (r = -0.153, p = 0.003). These trends held true for HF-FRAXBMD (r = -0.087, p = 0.094) and MOF-FRAXBMD (r = -0.111, p = 0.034), but only the latter reached significance. BMSi captures the cumulative effect of clinical risk factors in the FRAX algorithm, suggesting that it could provide additional information that may be useful in predicting risk of fractures. Further studies are warranted to establish its efficacy in predicting fracture risk.

Multiscale study on the compressive performance of diverse solid waste backfill bodies

To create green, low-energy self-compacting backfill materials, this study utilizes aeolian sand, slag, red mud, and calcium carbide slag to prepare diverse solid waste backfill materials in synergy. Additionally, a suitable amount of polypropylene fibers is added to enhance its toughness. During the experimental process, unconfined compressive strength tests were conducted using digital speckle technique. Computerized tomography scanning technology was employed for internal 3D visualization of the samples. Material strength difference mechanisms were characterized using SEM–EDS and XRD microscopic techniques. Finally, discrete element numerical simulation was utilized for analyzing the evolution of sample failure. The results show that with the increase in calcium carbide slag doping, the specimen UCS increases and then decreases, and when the doping of calcium carbide slag is 14%, the specimen UCS reaches a local maximum of 3.552 MPa; with the increase in the water–solid ratio, the specimen UCS gradually decreases, and when the water–solid ratio is 0.3, the specimen UCS reaches a local minimum of 3.26 MPa. With the increase in calcium slag doping, the mass percentage of calcium element and calcium-silicon ratio in the multi-solid waste matrix first increased and then decreased, and the micro-morphology of the multi-solid waste matrix included lamellar, block, and rod structures; With the increase in the water–solid ratio, the micro-morphology of the multi-solid waste matrix was gradually transformed, and the pore defects between the cementitious materials gradually increased. With the increase in calcium carbide slag doping, the porosity within the unit decreases, and when the doping of calcium carbide slag exceeds 14%, the porosity increases and the compressive strength decreases; with the gradual increase in the water–solid ratio, the porosity within the unit gradually increases, and the number of holes in the specimen reaches a minimum of 208 within the range of the study when the water–solid ratio is 0.24. Digital speckle technique and PFC numerical simulation together elucidate the sample’s failure process and crack evolution mechanism. Initially, the internal voids of the sample are gradually compacted, and crack propagation is slow. As the load increases to the peak, localized deformation and macroscopic crack formation occur in the sample. After the peak load, the sample exhibits significant displacement deformation, and the number of cracks increases significantly. The research findings can provide reference for the design and construction of solid waste backfill pipelines and trenches.

Effects of Pre-Deformation in Corrosion Fatigue Crack Growth of Al-Mg-Zn Alloy.

This study investigated the effect of pre-deformation on the corrosion fatigue crack propagation (CFCG) of Al-Mg-Zn alloy in a corrosive environment. Tensile tests at different pre-deformation levels and molecular dynamics simulations analyzed changes in dislocation density. Corrosion fatigue experiments were conducted in a 3.5% NaCl solution at room temperature, and crack propagation morphology was characterized using electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed that tensile strength increased by 2.63% and 10.00% for 5% and 10% pre-deformation, respectively. The crack propagation threshold values were L2 (6.36 MPa·m1/2) > L0 (6.05 MPa·m1/2) > L1 (5.13 MPa·m1/2), attributed to increased dislocation density and material strength. At 5% pre-deformation, dislocation pile-ups created stress concentrations that facilitated crack propagation. In contrast, the non-uniform dislocation distribution at 10% pre-deformation enhanced both material strength and resistance to crack growth.

Evaluation of Mechanical Properties of Sabai Grass (Eulaliopsis binata) Fibers and Epoxy Resin Composite Laminates Using Fly Ash as Filler Material

The integration of sabai grass fibers and fly ash in epoxy resin combines the strengths of both materials for developing a tailor-made composite laminate that balances performance, sustainability, and cost-efficiency. This innovative blend of natural fibers and industrial waste promotes environmental conservation. The laminates produced could also be used in diverse industrial and structural applications. This study investigated the mechanical properties of composite laminates reinforced with sabai grass fibers, fly ash filler, and epoxy resin as the matrix. In this work, the hand lay-up method was used to fabricate composites with two stacking configurations ((0°/0°/0°/0°) and (0°/90°/90°/0°)) and filler contents of 1.5 wt.%, 3 wt.%, and 5 wt.%. Various weight fractions of fly ash filler and sabai grass fiber were integrated into the epoxy resin to evaluate their impact on tensile strength, flexural strength, and hardness. The experimental results indicate that adding fly ash significantly improves the composite’s hardness to 27 HV in the composites containing 5 wt.% filler, while sabai grass fibers contribute to enhanced tensile strength and flexural strength. The composites with (0°/0°/0°/0°) fibers and 5 wt.% filler showed a higher tensile strength of 63.5 MPa and flexural strength of 118.5 MPa. The fractured sample was analyzed with the help of FESEM images. The XRD analysis confirmed the presence of fly ash components suitable for forming a bond with epoxy. EDX was conducted to determine the elemental composition of the fly ash. FTIR analysis verified the removal of impurities such as dust, dirt, and lignin from the fiber surface following NaOH treatment.