Flexural Strength Research Articles

Comparative effects of glazing versus polishing on mechanical, optical, and surface properties of zirconia ceramics with different translucencies.

This study compared the effects of glazing versus polishing on mechanical, optical, and surface properties of zirconia ceramics with different translucencies. In this in vitro study, 120 bar-shaped specimens (25 × 4 × 1.2 mm) were fabricated from three different types of zirconia with different translucencies (n = 40, DD Bio ZW, ZX2, and Cube X2). After sintering, each zirconia group was randomly divided into five subgroups of control (glazing), glazing + bur abrasion, glazing + bur abrasion + polishing with EVE Diacera® kit, glazing + bur abrasion + reglazing, and glazing + bur abrasion + polishing with EVE Diacera® kit + reglazing. The specimens underwent surface roughness, hardness, flexural strength, and translucency tests, as well as X-ray diffraction (XRD) and scanning electron microscopy (SEM) for assessment of surface topography. Data were analyzed by one-way analysis of variance, Tukey test, and Pearson test (α = .05). Flexural strength, surface hardness, and translucency were significantly correlated with zirconia type. ZW zirconia had significantly higher flexural strength and surface hardness and significantly lower translucency than Cube X2 and ZX2 (p < .001). Surface roughness had no significant correlation with zirconia type (p = .274). Polishing created the smoothest, and bur abrasion created the roughest surface (p < .001). Flexural strength and hardness in most experimental groups were significantly lower than in the control group (p < .001). Translucency was not significantly different in bur abrasion and polishing groups, compared with the control group; however, reglazing significantly increased the translucency (p < .001). SEM micrographs confirmed the surface roughness results. XRD showed monoclinic phase only in reglazed groups. Of different surface treatments, polishing improved the surface properties and caused the smallest change in mechanical properties of zirconia with different translucencies.

Efficacious application of data-driven machine learning models for predicting and optimizing the flexural tensile strength of fiber-reinforced concrete

In the literature, a limited number of studies have utilized the random forest (RF) technique to model the flexural tensile strength (FTS) of steel fiber reinforced concrete (SFRC). This study established modeling of the FTS of SFRC containing mono-fibrous (exclusively crimped and hooked) systems. A comprehensive database of 193 records was used from 18 published studies (including 30 documents sampled by authors). Machine-learning numerical models were developed and evaluated. Partial dependence plots were constructed to visualize the relationship between the model parameters and rank the parameters based on their importance. It has been found that the RF model can be rationally used to predict and optimize the FTS of SFRC, as most of the predicted–tested results were close to the ±80% accuracy range. The model showed of underestimation nature for SFRC with high FTS values. The Gini index-based importance analysis showed that the fiber’s content and tensile strength had the highest significance among the other variables. A drastic increase in the FTS by an increase in the fibrous dosage was achieved. However, no major SFRC’s tensile strength enhancement for dosages was more than 1.5%, while its optimum diameter was 0.5–0.7mm. The results also illustrated that the effect of the fiber’s length is quite similar to that of the fiber content. However, no significant increase can be achieved by increasing the fiber’s length from 40 to 60mm.

Mechanical and durability performance of self-compacting mortars made with different industrial by-products as fillers

This study evaluated the performance over time of Self-Compacting Mortars (SC mortars) with different industrial by-products simultaneously; Electric Arc Furnace Dust (EAFD) and fly ash, conforming (FA) or not conforming (NcFA), from coal-fired power plant or recovery filler from hot-mix asphalt plant (RF). Different SC mortars mixes were produced; three mixes with different EAFD ratio incorporation (0 %, 10 %and 20 %) for each the other industrial by-products (FA, NcFA and RF) substituted of cement at 30 %; and additional three mixes with 60 % of cement replacement by FA and the same EAFD incorporation ratios. To study the performance over time of these SC mortars, tests such as electrical resistivity, ultrasonic pulse velocity, drying shrinkage, capillarity, compressive and flexural strength were carried out up to 91 days of curing. The SC mortar compositions was evaluated by TGA/DTA and DRX analysis. Previously, the by-products used were characterized. The EAFD incorporation showed a strong influence in SC mortars, independently of the industrial by-product used. The initial inhibition of development of hardening in SC mortars due to the presence of ZnO in EAFD was lifted over time up to some extent. The simultaneous use of different industrial-by products in SC mortars in high volume content walks towards the sustainability in the construction sector.

Experimental study on properties of cinder aggregate lightweight concrete with fibre reinforcement

Lightweight concrete is gaining increasing significance in the construction industry due to its numerous advantages over conventional concrete. It can be produced by partially or fully replacing conventional coarse aggregates with lightweight aggregates. Laboratory tests were conducted to assess the feasibility of utilizing solid waste, such as cinders, for manufacturing lightweight aggregate concrete. The mechanical properties of cinder aggregate lightweight concrete were improved through the introduction micro-reinforcements. Polypropylene fibres were incorporated as micro-reinforcements at volume fractions of 0.1%, 0.2%, 0.3%, and 0.4%. The experimental results, including compressive strength, flexural strength, and modulus of elasticity, demonstrated that waste cinder aggregates can effectively replace coarse aggregates in lightweight concrete. Furthermore, the incorporation of polypropylene fibres enhances the mechanical performance of cinder aggregate lightweight concrete.

Assessing the suitability of fused deposition modeling to produce acrylic removable denture bases.

To study the feasibility of using poly methyl methacrylate(PMMA) filament and fused deposition modeling (FDM) to manufacture denture bases via the development of a study that considers both conventional and additive-based manufacturing techniques. Five sample groups were compared: heat and cold cured acrylic resins, CAD/CAM milled PMMA, 3D-printed PMMA (via FDM), and 3D-printed methacrylate resin (via stereolithography, SLA). All groups were subjected to mechanical testing (flexural strength, impact strength, and hardness), water sorption and solubility tests, a tooth bonding test, microbiological assessment, and accuracy of fit measurements. The performance of sample groups wasreferred to ISO 20795-1 and ISO/TS 19736. The data was analyzed using one-way ANOVA. Samples manufactured using FDM performed within ISO specifications for mechanical testing, water sorption, and solubility tests. However, the FDM group failed to achieve the ISO requirements for the tooth bonding test. FDM samples presented a rough surface finish which could ultimately encourage an undesirable high level of microbial adhesion. For accuracy of fit, FDM samples showed a lower degree of accuracy than existing materials. Although FDM samples were a cost-effective option and were able to be quickly manufactured in a reproducible manner, the results demonstrated that current recommended testing regimes for conventionally manufactured denture-based polymers are not directly applicable to additive-manufactured denture base polymers. Therefore, new standards should be developed to ensure the correct implementation of additive manufacturing techniques within denture-based fabrication workflow.

Sustainability assessment and mechanical characteristics of high strength concrete blended with marble dust powder and wheat straw ash as cementitious materials by using RSM modelling

Research into environmentally favorable alternatives to conventional concrete, such as reengineering techniques and the recycling of industrial and agricultural waste, has increased dramatically over the past decade. This research intended to examine the potential benefits of utilizing wheat straw ash (WSA) and marble dust powder (MDP) as supplementary cementitious materials (SCM) in high-strength concrete (HSC). The intention is to decrease carbon dioxide emissions and the amount of Portland cement (PC) required. Concrete formulations containing 0%, 15%, 20%, 30%, and 40% by weight of MDP and WSA as SCM, respectively, were evaluated by using response surface methodology (RSM) modelling for multi-objective optimization. This research assessed the environmental ramifications of employing WSA and MDP as SCM in HSC. Specifically, it examined the impacts on embodied carbon and eco-strength efficiency. Cubical specimens underwent a series of tests to attain the desirable compressive strength of approximately 60 MPa after a period of 28 days. The workability of green concrete decreased as the proportion of WSA and MDP used as SCM increased, according to the study. The optimum compressive strength, flexural strength, splitting tensile strength, and modulus of elasticity of HSC was recorded by 68 MPa, 5.98 MPa, 4.25 MPa, and 40 GPa, at 15% of SCM (composed of 10% WSA and 5% MDP) at 28 days respectively. Using ANOVA, response prediction models were validated and developed with a confidence level of 95%. In summary, the increased application of 20% WSA and 20% MDP as SCM in concrete leads to a 31.64% reduction in the carbon footprint of the material.

Preparation of a novel foamed concrete modified with carbon fiber and graphite: Mechanical, electro-magnetic and microstructural characteristics based on X-CT

In this paper, foam concrete is modified using graphite and carbon fiber as absorbents. The mechanical properties are analyzed in conjunction with hydration products, pore size distribution based on XCT test. Additionally, the resistivity, complex permittivity and complex permeability are tested. The results demonstrate that carbon fiber enhances the proportion of pores with diameters less than 200 μm in foam concrete, thereby significantly enhancing its flexural strength. Furthermore, incorporating graphite helps offset the initial retardation of sulfoaluminate cement hydration induced by carbon fibers, leading to an increase in the average pore size and a reduction in compressive strength. The incorporation of carbon fibers at a concentration of 0.6wt.% achieves the percolation threshold, akin to scenarios with singular fiber incorporation. Exceeding 2wt% graphite content results in negligible influence on the conductivity. The synergistic integration of graphite and carbon fibers significantly improves the electromagnetic wave absorption performance of the composite. At a thickness of 6 mm, the material exhibits an effective bandwidth where the reflection loss is less than -10 dB, extending up to 2.5 GHz, which constitutes 52.08% of the tested frequency spectrum.

Effects of heat treatment on the mechanical properties of 3D-printed polylactic acid: Study of competition between crystallization and interlayer bonding

Fused deposition modeling (FDM) is a popular additive manufacturing technique because of its flexibility, customization, cost-effectiveness, and eco-friendliness. However, due to the layer-by-layer fabrication process and the formation of voids, the mechanical properties of printed parts are lower than other manufacturing techniques. As a solution, heat treatments can effectively mitigate additive manufacturing limitations and improve the mechanical properties of printed parts. The interlayer bonding and subsequently mechanical properties of 3D-printed PLA were affected by the competition between crystallization and chain diffusion of 3D-printed polylactic acid during the heat treatment process. This competition highlights the importance of optimization of heat treatment. Additionally, crystallite growth could cause a reduction in some mechanical properties, like elongation. The size, distribution, and content of voids are also influenced by heat treatment, playing a crucial role in the mechanical properties of 3D-printed parts. In this research, printed samples were heat-treated at temperatures of 75 ºC, 110 ºC, and 130 ºC for two hours. Furthermore, compression-molded samples were fabricated to inspect a comparison of mechanical properties between the traditional and additive manufacturing methods and investigate the effect of layer-by-layer fabrication on these properties. Sample AM-75 showed a 15.5% improvement in bonding strength compared to the non-annealed printed sample, resulting in an increase of 20.2% in tensile strength and 275% in impact strength. Moreover, annealing the sample at 130 ºC resulted in a 7.6% reduction in porosity and a significant improvement of 220% in crystallinity, heat deflection temperature, flexural modulus, and flexural strength, with improvements of 121%, 29.5%, and 15.2% respectively.

Interface engineering in CF/Al matrix composites for enhancement in mechanical strength and anti-corrosion properties

Metal matrix composites (MMCs), renowned for their lightweight and exceptional mechanical properties, are currently in high demand. Herein, carbon fiber‑aluminum metal matrix composites (CF/Al MMCs) modified with 4 types of corrosion-barrier interface coatings (CBCs), respectively, including Ni, TiO2, ZnO, and Al2O3 were investigated, and the composites were prepared by squeeze casting technique. The effects of these CBCs on the CF/Al interface reaction and the mechanical properties and electrochemical corrosion resistance of the composites are revealed and discussed thoroughly. It is observed that T300‑carbon fiber reinforced MMCs without any CBCs exhibit low mechanical strength due to the formation of Al4C3 phase induced by strong interaction between fiber and matrix. With CBCs, the formation of Al4C3 was significantly suppressed. Comparatively, the ZnO-coated CF/Al MMCs exhibit the most remarkable enhancement in the mechanical properties with a flexural strength of 796.4 MPa and a modulus of 105.3 GPa, which are approximately 114% and 52.2% higher than those of the counterparts without CBCs, respectively. More importantly, the CF/Al MMCs with CBCs demonstrate superior chemical corrosion resistance, retaining their mechanical performance even after a 7-day immersion in salt solutions. These results provide an important guideline in interface engineering for MMCs with enhanced mechanical properties and electrochemical corrosion resistance.

An Experimental Study of Strength Properties of Galvanized Iron (GI) Fiber Reinforced Concrete

Abstract: Fiber Reinforced Concrete is one of the most quality construction techniques of modern times. The utilization of locally available galvanized iron or metallic fiber as a bridging material. The concrete with metallic or nonmetallic fiber is very useful and its enhanced concrete mechanical properties. Therefore, a research has been conducted to study the performance of locally available GI wire fiber reinforced concrete (GWRC). This paper presents the findings of the research that made an effort to explore several basic characteristics of GWRC primarily related to strength, ductility and durability. This research was, therefore, conducted to compare the concrete strength performance of GI fiber with different lengths and a control specimen. The objective of this study is to explore the effect of GI fiber in terms of compressive strength, splitting tensile strength, and flexural strength with ‘Galvanized Iron’ fiber using several cutting lengths of 25 mm and 35mm with various mix proportions including 1.0%, 1.5%, 2.0%, and 2.5% by weight of the concrete

Determination of Mechanical Properties of Hybrid Composite

Abstract: Manufacturing of composite laminates is the peculiar member of science that encounter its immense utilization in various industrial areas such as sporting, automotive, aerospace and marine industries. The superior properties of composites such as stiffness, better mechanical properties, low density, and lightweight make it a candidate in engineering applications. The continuous research in this area is due to the need for seeking alternative materials with increased performance. In this report, the basalt fiber E-glass reinforced composite mechanical properties has investigated. The basalt fiber E-glass composite was formulated with hand layup moulding technique. Mechanical properties such as tensile, flexural strength and impact strength of the basalt fiber E-glass composite have been analysed

Experimental Investigation of Partial Replacement of Cement in Concrete using Waste Glass Powder

Abstract: The construction industry is the second largest industry in the world &amp; concrete is prime material used in it [5]. The use of concrete generates lots of heat during hydration process. It directly contributes to global warming. Also cement is costly material &amp; its storage is also difficult. The cement plays important role of binding in concrete. It contains lime as main constituents. So to reduce this ill effect of cement one must find the alternatives for cement which can perform the same role in concrete. This study represents the experimental investigation of effect of partial replacement of cement by glass powder on strength of concrete &amp; other factors like workability, water cement ratio, and heat of hydration. Glass contains lime as its one of main constituent. The cement was replaced with glass powder by 5%, 10%, 15%, and 20%. The compressive strength, flexural strength &amp; split tensile strength are tested for these replacements. Also economical aspect is observed along with. It is observed that physical &amp; chemical properties of glass are almost similar to cement. So in this study an attempt is made to investigate the effect of partial replacement of cement by glass powder in concrete to make it as a special concrete

Investigation of Mechanical Properties of Natural Fiber Reinforced Hybrid Composite

Abstract: Hybrid composite is a material composed of matrix and two or more reinforcements. Two or more reinforcements in hybrid composite replace the limitation of conventional composites by providing uniform strength to thematerial. Recently, natural fibers reinforced hybrid composites are gaining increased interest due to the encouraging properties of natural fibers such as high strength to weight ratio, low cost, no harm to environment etc. Many studies dealt with natural fibers based composite reported that the hybrid composites has the potential to replace glass fiber based composites and to reduce the weight of conventional composite. This project reports on the manufacturing of the Indian elm and Acacia fibre reinforced epoxy composite laminate as per the ASTM (American Society for Testing and Materials) Standards. This laminate consists of matrix and reinforcement. Epoxy is used as a structural matrix material which is then reinforced by Indian elm fiber, combining Acacia fibres with resin matrix results in composites that are strong, lightweight, corrosion-resistant and dimensionally stable. They also provide good design flexibility, high dielectric strength and act as inflammable materials. Their tremendous strength-to-weight and design flexibility make them ideal in structural components for the aerospace industry. In this project the Indian elm and Acacia fibre reinforced epoxy composite is manufactured into two different parts each having ratios of Indian elm and Acacia fibre to epoxy resin as 60:40, 40:60 respectively and are compared for ultimate tensile strength, impact strength, hardness strength and flexural strength of the material by conducting experiment such as tensile test, flexural test, hardness test and impact test.

An Experimental Investigation on Mechanical Properties of Bacterial Concrete Using Bacillus Subtilis

Abstract: This Concrete is susceptible to micro crack formation and has pores which are highly undesirable because they provide an open pathway for the ingress of water and other deleterious substances. The use of concrete surface treatments with water proofing materials to prevent the access of aggressive substances is a common way of contributing to concrete durability. However, the most common surface treatments use organic polymers (epoxy, acrylics and polyurethanes) all of which have some degree of toxicity. Bio inspired materials can lead to a more sustainable construction industry, especially when providing new low toxic solutions. Hence, there is an urgent need to pay more attention for improving the properties of concrete with respect to strength and durability, especially in aggressive environments. One effective remedy for closure of cracks is the Bacterial Concrete (BC) which will continuously deposit calcite in concrete. This, phenomenon is called as Microbiologically Induced Calcite Precipitation (MICP). The urease enzyme enables the deposition of calcium carbonate (CaCO3) with the help of bacteria. The bacterial remediation technique surpasses other techniques as it is bio-based, eco-friendly and durable. Bacteria need to offer resistance to withstand high pH of concrete and mechanical stresses during mixing. In these present investigations bacterial sample name Bacillus Subtilis (BS) is considered in concentrations of 104 , 105 and 106 cells/ml of mixing of water. investigations are carried out on strength-related properties such as compressive strength, splitting tensile strength and flexural strength to assess the quality of concrete. The optimum dosage of cell concentration of bacteria is found to be 105 cells/ml for BS based on compressive strength results. M25 grade concrete is designed and used for embedding Bacillus subtilis bacteria.

Effect of printing parameters on impact energy absorption of additively manufactured hierarchical structures

Purpose This study aims to examine how the thickness of layers and printing speed impact the energy absorption capacity of honeycomb structures through drop-weight experiments. In addition, the effect of printing orientation on the resulting microstructure and mechanical performance was targeted to be examined. Design/methodology/approach In this paper, after manufacturing test specimens using fused deposition modeling technique with three distinct layer thicknesses (0.16 mm, 0.20 mm and 0.28 mm) and printing speeds (40 mm/min, 50 mm/min and 70 mm/min), drop weight tests were carried out. Then to see the effect of printing orientation on mechanical performance, three-point-bending tests were performed and damage mechanisms were comparatively examined through scanning electron microscopy. Findings An increase in layer thickness from 0.16 mm to 0.28 mm resulted in a notable 37% decrease in the impact resistance of the printed part. In addition, increasing the printing speed from 50 to 70 mm/min reduced the energy absorption capacity of the printed part by approximately 36.5%. Moreover, in terms of printing direction, transversely printed specimens showed 10% lower flexural strength than longitudinally printed specimens. Finally, scanning electron microscopy (SEM) observation showed that internal defects were more prominent in transversely printed specimens, resulting in premature failure. Furthermore, delamination was also detected in transversely printed specimens as another damage mechanism accelerating material failure. Originality/value It is seen that the effect of printing parameters on the fundamental mechanical properties including tensile strength, strain at break, ductility and elastic modulus were studied by various researchers. However, to the best of authors’ knowledge, the effect of printing speed and layer thickness on the energy absorption of polylactic acid based hexagonal honeycomb was not encountered. In addition, in-depth SEM analysis to discover the influence of printing direction significantly contributes to the literature.

Enhanced Mechanical and Thermal Properties of Alkali-Treated Coir Fibres Incorporated with Murraya Koenigii: A Comparative Study of Mono-Layer and Tri-Layer Biocomposites

This study examined the surface morphology and thermal behaviour of the coir fibres incorporated with murraya koenigii before and after alkaline treatment. The mechanical properties of biocomposites reinforced by the untreated fibres, treated fibres, mono-layer and tri-layer treated fibres incorporated with murraya koenigii were systematically investigated. The experimental results showed significant enhancements in tensile strength, flexural strength, hardness, and impact resistance of the biocomposites reinforced by treated fibres. Notably, the alkaline treatment has produced a rougher surface on coir fibres, promoting improved mechanical interlocking between the fibres and the polyethene matrix. These effects become more significant when murraya koenigii particles are incorporated into the fibres. It was found that the tri-layer treated fibres incorporated with murraya koenigii biocomposites showed higher tensile and flexural strength, superior hardness and impact strength when compared to the mono-layer reinforcement biocomposites. At higher temperatures, the treated fibres showed better thermal stability than the untreated fibres and polyethene. Incorporating murraya koenigii particles increased the thermal resistance of the treated fibres, revealing the potential of this green synthesis approach for the development of thermally stable natural fibre composites.

Development in the Study of Mechanical Prop-erties and Damage Constitutive Models of Rub-ber-Reclaimed Concrete

Advances in rubber-reinforced concrete technology and its applications in engineering are cru-cial for the thorough recycling and safe disposal of waste tire rubber and construction debris. Rubber-reinforced concrete (RAC) is a concrete material produced by substituting some fine and coarse aggregates with waste rubber particles and recycled aggregates. The incorporation of waste rubber particles endows RAC with distinctive mechanical properties and a distinct damage constitutive model. The mechanical properties of rubber recycled concrete mainly in-clude compressive strength, tensile strength, flexural strength, and elastic modulus. Compared to traditional concrete, RAC exhibits slightly lower compressive and flexural strengths but sig-nificantly enhanced tensile strength. This is due to the changes in mechanical properties caused by the softness and elastic properties of rubber particles. In addition, the addition of rubber particles can also improve the energy absorption capacity and impact resistance of concrete. On the other hand, in order to describe the damage behavior of rubber recycled con-crete, some constitutive models were studied. Common models include linear elastic model, plastic model, and damage model. The linear elastic model is suitable for describing the be-havior of rubber recycled concrete during the elastic stage; The plastic model is suitable for describing its deformation behavior during the plastic stage; The damage model can better describe the fracture and failure behavior of rubber recycled concrete, including shear damage, tensile damage, and compression damage. Tailored to the unique characteristics of RAC, these models consider the stiffness of rubber particles and the deformation characteristics of the binding materials, enabling accurate predictions of the stress-strain behavior of RAC. In conclusion, rubber-reinforced concrete possesses excellent mechanical and durability proper-ties, which can be accurately described and predicted using appropriate constitutive models. These findings are crucial for advancing the application and development of rubber-reinforced concrete.

Experimental investigation of mechanical properties and multi-objective optimization of electronic, glass, and ceramic waste-mixed concrete.

The utilization of waste from various sources plays an important role in minimizing environmental pollution and civil construction costs. In this research, the mechanical properties of concrete were studied by mixing electronic waste (EW), glass powder (GW), and ceramic tile waste (CW). The effects of weight percentages of EW, GW, and CW are considered to investigate improvements in mechanical properties such as compressive strength (CS), split tensile strength (STS), and flexural strength (FS) of concrete. Taguchi analysis has been applied to predict the optimum composition of waste mixing percentages. The Multi-Objective Optimization Ratio Analysis (MOORA) techniques are applied to estimate the optimum composition of mixing wastes for maximizing the CS, STS, and FS of concrete. It was observed that 10 wt.% of EW, 15 wt.% of GW, and 30 wt.% of CW are predicted as the optimal mixing combinations to obtain a maximum compressive strength of 48.763 MPa, a split tensile strength of 4.178 MPa, and a flexural strength of 7.737 MPa, respectively. Finally, the predicted optimum waste-mixed weight percentages were used to examine the microstructure and various elements in the concrete using SEM and XRD analysis. When compared to conventional concrete, the optimum waste-mixed concrete has improved its compressive strength (38.453%), split tensile strength (41.149%), and flexural strength (36.215%).

Nano-SiO2/polyurethane modified unsaturated polyester resin mortar for thin layer repairing on airport pavement

This paper introduces a novel toughened polymer mortar designed for runway repair, featuring outstanding impact resistance, high strength, and cost-effectiveness. To augment the toughness of unsaturated polyester (UP) polymer mortar, nano-SiO2 and polyurethane (PU) were incorporated. Firstly, the optimal dosages of nano-SiO2 and PU were determined through tensile test and impact test. Then, the modification mechanism of nano-SiO2/PU on UP resin was explored by microscopic image technology. In addition, the compression, flexural, fluidity, flexural bond strength and construction time tests were carried out to determine the optimal formula of nano-SiO2/PU modified UP resin mortar. Finally, the durability, impact resistance, impermeability resistance, skid resistance, and interlayer bond strength of modified UP resin mortar were studied and compared with those of pure UP resin mortar and epoxy (EP) resin mortar. Results show that the optimum proportion by mass for nano-SiO2/polyurethane modified UP resin is, UP resin: PU: dibutyltin dilaurate: nano-SiO2: initiator: accelerator: diluent: plasticizer = 1: 0.1: 0.002: 0.01: 0.01: 0.01:0.15:0.01. Furthermore, the mass proportion of modified UP resin to aggregate is 1: 1.2. In nano-SiO2/PU modification of UP resin, the -NCO groups of PU have been involved in chemical interaction with the -OH group of UP, while nano-SiO2 and UP resin are blended physically only. Compared with pure UP resin mortar, the nano-SiO2/PU modified UP resin mortar exhibited a 44% reduction in shrinkage rate, approximately 20% less corrosion loss, a 32% decrease in freeze-thaw loss, a 37% improvement in impact resistance, and increased shear bonding strength, flexural bonding strength, and tensile bonding strength by 44%, 33%, and 47%, respectively. Although the modified UP resin mortar demonstrated slightly lower performance in terms of dry shrinkage, corrosion resistance, skid resistance, and tensile bond strength compared to EP resin mortar, its freeze-thaw durability, impact resistance, flexural bond strength, and shear bond strength surpassed those of EP resin mortar. All three materials exhibited excellent impermeability. Leveraging the advantages of PU and nano-SiO2, the modified UP resin presents a promising repair material for airport pavement with enhanced toughness, high stability, and reduced cost.

On the bending behavior of hybrid fiber–metal laminates (HFMLs) based on aluminum and glass/Kevlar fibers reinforced epoxy

In this work, the mechanical behaviors under flexural loading of fiber–metal laminates (FMLs) comprised of an aluminum alloy reinforced with glass fibers (GFs) and Kevlar fibers (KFs) embedded in an epoxy composite are experimentally investigated. For this purpose, non-FMLs, FMLs, and hybrid FMLs (HFMLs) are tested and their results are compared in terms of the flexural strength and modulus, strain to failure, toughness, interlaminar shear strength (ILSS), and specific properties. Results show that the incorporation of GFs on the compression side and KFs on the tensile side improves the bending properties of the HFMLs compared to the KF-based FMLs, which enhances the laminates’ resistance to bending loads. The HFMLs exhibit improvements of 24%, and 5% in flexural strength and modulus, respectively, compared to the KF-based FMLs. Moreover, hybridization significantly improves strain to failure by up to 115% compared to the GF-based FMLs. Additionally, the ILSS analysis reveals improved values in FMLs compared to non-FML samples, when GF-based FMLs demonstrate higher ILSS than KF-based ones, which can be attributed to GFs’ stiffness and high-quality bonding with the aluminum sheets. HFMLs attain a 19% improvement in ILSS compared to the KF-based FMLs. The failure mechanism depends on the intrinsic features of the studied fibers, while the studied FMLs display better damage tolerance. In this context, the HFMLs present enhanced toughness, delamination resistance, and the ability to prevent crack propagation, positioning them as promising candidates for lightweight structural applications where a balance between strength, stiffness, and toughness is required.