Improvement In Flexural Strength Research Articles

Multi-scale characterization of lightweight aggregate and superabsorbent polymers influence on autogenous shrinkage and microstructure of ultra-high performance concrete

This study investigates the effects of internal curing agents on the autogenous shrinkage, hydration, and microstructure of ultra-high-performance concrete (UHPC). Lightweight aggregate (LWA) and superabsorbent polymers (SAP) were examined across various dosages as representative internal curing agents. Measurements were taken for the mechanical properties, autogenous shrinkage, and internal relative humidity of the UHPC. The mechanisms of internal curing were analyzed using thermogravimetry, pore structure, and microstructural evaluations. Additionally, porosity and microhardness in the matrix around the fibers and internal curing agents were tested to quantitatively assess their impact on the properties of the UHPC matrix. Results indicate that high dosages of LWA or SAP negatively affect the compressive strength of UHPC. A dosage of 15 % LWA increased flexural strength by 11 %, whereas SAP showed no significant improvement in flexural strength. LWA effectively reduced autogenous shrinkage by 49.4 %-88.8 %, while a SAP dosage of 0.3 % reduced autogenous shrinkage by 82 %. Both LWA and SAP increased porosity by 33.9 %-55.9 %. SAP released water within the matrix, forming voids filled with calcium hydroxide. The interface between LWA and the matrix was dense, with porosity near the LWA and SAP interfaces being 23.5 %-53.9 % and 26.0 %-38.2 % lower, respectively, compared to other areas. The microhardness in the LWA and SAP interface regions was 20 % and 16.2 % higher than in different places. The LWA pre-saturated method can effectively reduce autogenous shrinkage, and 15 % LWA has no adverse effect on mechanical strength.

Optimizing concrete performance with polymer-cement networks: enhanced flexural strength and crack resistance

Concrete is a building material known for its high compressive strength but susceptibility to cracking. Once concrete cracks, moisture, aggressive ions, and air can easily penetrate its body, deteriorating its mechanical properties and durability. Herein, polyacrylamide (PAM) is incorporated into the concrete via in situ polymerization of acrylamide (AM) to construct a polymer-cement network, aiming to improve flexural strength and crack resistance. Incoporating 7% AM, the initial cracking fracture toughness is increased by 47.5%. Concrete with 10% AM exhibits a 28-day flexural strength of 19.38MPa, 65.5% higher than normal concrete. The polymer network formed by in situ polymerization of AM crosslinks with cement hydrates to construct the polymer-cement network, which is responsible for the improvement of flexural strength and crack resistance. Upon completion of the polymerization reaction, the aggregate and the cement matrix are bridged by polymer, concomitant with the densification of the interfacial transition zone (ITZ). In situ polymerization of AM is found to be more efficient and effective than directly adding PAM in improving flexural strength. Moreover, refinement of the pore structure is also observed by in situ polymerization of AM. In conclusion, our study presents a convenient and efficient approach to improving the crack resistance of concrete, thereby spurring the development of high performance concrete.

A comparative study of strength and surface properties of permanent 3D-printed resins with CAD-CAM milled fixed dental prostheses.

To compare the strength, surface roughness, and hardness of newly introduced permanent three-dimensional (3D)-printed resin in comparison with computer-aided design and computer-aided manufacturing (CAD-CAM) milled materials. Three 3D-printed resins (NextDent C&B, Formlabs Permanent Crown, and VarseoSmile Crownplus) and two CAD-CAM milled (IPS e.max ZirCAD LT and VITA Enamic) resins were used to fabricate discs specimens. A total of 200 disc specimens were fabricated according to manufacturer recommendations. Within each group, half of the specimens were subjected to thermal cycling (5°C-55°C, the 30s, 5000 cycles). Aged and nonaged specimens were evaluated for biaxial flexural strength (BFS), surface roughness, and hardness. Results were statistically analyzed using analysis of variance (ANOVA) and t-tests (α=0.05). Significant differences (p<0.05) were observed in the BFS, surface roughness, and hardness between the 3D-printed and milled groups, before and after thermal aging. Overall, the CAD-CAM milled ceramic group had superior strength, surface roughness, and hardness when compared to all other groups (p<0.001), except for surface roughness after thermal aging, which was similar in all groups (p=0.063). Within each group, there was no significant difference (p>0.05) in surface roughness after thermal aging. BFS values of 3D-printed materials were statistically similar. In terms of surface roughness, Formlabs specimens displayed the highest value before and after thermal cycling, when compared to other 3D-printed materials. Regarding hardness, the VarseoSmile Crown plus group demonstrated the highest values compared to other 3D-printed materials, before and after thermal cycling. Permanent 3D-printed resins have lower strength than CAD-CAM milled materials. 3D-printed permanent resin materials exhibited high roughness and comparable hardness to CAD-CAM materials. Thermal aging negatively affected the properties of 3D-printed permanent crowns. Owing to the low strength of 3D-printed permanent resins, they may not be recommended for clinical practice until further improvements in flexural strength are made to meet clinical standards.

Mechanical Performance Enhancement of Alkali-Activated Composites Using Synthetic Fibers with Metazeolite and Aluminum Sludge-Based Recycled Concrete Aggregates

This study examines the substantial enhancement in the performance of alkali-activated composites (AACs) produced from a distinctive combination of metazeolite (MZ) and slag (S), reinforced with synthetic fibers, and augmented with aluminum sludge (AS) and recycled concrete aggregate (RCA). The composites were subjected to activation through the use of a specific sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) blend in a 2:1 ratio, with an activator-to-binder ratio of 0.95. Through a process of experimentation, the research team identified an optimal mix by varying the molarities of sodium hydroxide (NaOH) between 8M and 14M and the ratios of metazeolite to slag between 25% and 100%. The aforementioned mixture, comprising 50% MZ and 50% S, was activated with 12M NaOH and enhanced with 30% aluminum sludge, exhibiting remarkable strength characteristics. Furthermore, the incorporation of synthetic fibres, including polyethylene (PEF), polyamide (PAF), and basalt fibers (BF), resulted in a notable enhancement of the material's performance. It is noteworthy that the addition of basalt fibers at a concentration of 0.5% resulted in a 7% increase in compressive strength and a 24% improvement in flexural strength. This pioneering research illuminates the transformative potential of MZ-S-based AACs, particularly when combined with AS and BF, paving the way for the development of sustainable construction materials that meet contemporary performance and environmental standards.

Durable polymer composites preparation with oxy-delignified banana fiber for automotive parts: A study on mechanical and thermal properties

An innovative process route has been developed to produce modified banana fiber that are used as reinforcement in polypropylene composites for automotive parts. Banana fiber (BF) is modified through, Alkaline peroxide (APF), and oxygen delignification (ODF) treatment to obtain better adhesion and enhanced thermo-mechanical properties. The fiber-reinforced polymer (FRP) composites (10–30 % loading), were prepared through a specified configuration in a co-rotating twin screw extruder followed by injection molding. The results show that the ODF treatment with a 15 % NaOH concentration resulted in an 11-kappa number, which was lower than APF and untreated fiber. The highest improvement in tensile (31.27 ± 2.56) and flexural strength (44.880 ± 1.05 MPa) was achieved for ODF polymer composite and were 20.40 % and 35.6 % higher compared to the untreated fiber. The addition of natural fiber decreased the melt flow index to 7.56 gm/10 min with a slight decrease in hydrophilicity. The thermal stability was increased with enhanced melting, crystallization temperatures, and surface morphology.

Method to improve the bonding strength of polyethylene terephthalate core with glass fiber reinforced skins in a sandwich composite

AbstractComposite materials provide an alternative to conventional structural materials. Sandwich composites show high bending strength and superior strength‐to‐weight ratio. The major drawback in sandwich composites is debonding of skin from core, that causes failure of a component during the usage at different loads. To overcome this issue, the current work identifies a solution of introducing nylon screws (M6 × 32) to adhere firmly the skins consisting of glass fibers with PET (Polyethylene Terephthalate) core. The sandwich composites were fabricated by vacuum infusion process. Two flat sandwich composites were fabricated; one with nylon screws placed perpendicular to the skin and the other a plain sandwich composite. Mechanical characteristics of the specimens such as fracture toughness, flexural strength and shear strength were studied. Specimens with nylon screws showed 21.78% more fracture toughness compared to plain specimen. The presence of screws acts as hindrance to the propagation of cracks in the interfacial region resulting in the enhancement of debonding resistance of the specimens. Also, sandwich specimens with nylon screws exhibited 136% and 142% improvement in flexural and shear strength respectively when compared to plain sandwich specimens. The investigation of scanning electron microscope (SEM) images of tested specimens indicates strong interfacial bonding between skin and the core of specimens with nylon screws.Highlights Introduction of light‐weight nylon screws in z‐direction enhanced the bonding between face sheets and foam core. Sandwich composites with nylon screws exhibited superior bending and shear strength compared to plain specimens. Crack propagation in the interfacial region is restricted by the presence of nylon screws. Investigation of fractured specimens indicated a strong interfacial bonding in the specimens with screws.

Dipodal silane‐treated ramie woven matt reinforced polylactic acid biocomposites for improved mechanical and thermal properties

AbstractHot compression molding was used to produce biocomposites from ramie plain‐woven fabric‐reinforced polylactic acid (PLA). Prior to composite fabrication, alkali and dipodal silane (bis(3‐trimethoxysilylpropyl) amine) (BAS) were applied to improve fiber‐matrix adhesion. Mechanical tests revealed improvements in tensile and flexural strength due to interfacial adhesion. The flexural strength of ramie PLA composite samples treated only with silane (SR‐PLA) was the highest, at 136.35 MPa. Young's modulus was 7.51 GPa. BAS treatment was crucial for ensuring strong adhesion between the fabric and the PLA matrix. In combined alkali‐BAS‐treated composites (ASR‐PLA), the glass transition and crystallization temperatures disappeared completely, affecting PLA morphology. The maximum heat of absorption (373°C) was found in SR‐PLA composites, suggesting electrostatic interactions created a three‐dimensional network. In conclusion, the initial incorporation of dipodal silane resulted in the formation of six silanol linkages with ramie fabric, leading to enhancements in the mechanical and thermal characteristics of ramie–PLA composites.Highlights Alkali and BAS treated Fabrics ironed to remove treatment‐induced wrinkles. Carded PLA fiber with consistent density and weighted in four equal portions. Fabric and PLA lay alternatively in warp direction before compression molding. SR‐PLA composites exhibited improved thermal and mechanical properties.

From Waste to Strength: A Comprehensive Review on Using Fly Ash in Composites with Enhanced Mechanical Properties

This article explores the diverse applications of fly ash (FA), a by-product generated during the combustion of coal. The introductory segment thoroughly comprehends the origins, composition, and widespread occurrence of FA. FA, which comprises an estimated 38% of worldwide power generation, frequently encounters disposal and storage obstacles on account of its classification as non-hazardous waste in the majority of countries. The environmental issues linked to the dispersal of FA are underscored in the problem statement, which further emphasizes the urgency for sustainable alternatives. Due to the fugitive emissions and potential health hazards associated with metal melting in FA, it is critical to investigate novel applications and disposal techniques immediately. Environmental sustainability is a primary focus of research, with the development of synthetic FA composites being one such alternative. The analysis presents significant findings that underscore the wide-ranging applications of FA. These applications include its utilization as a filler in composites, as well as its incorporation into cement and geo-polymerization processes. Notably, (10-20) wt. % Nano-FA enhances epoxy-based composites, showcasing remarkable improvements in tensile strength, flexural strength, and impact resistance. In thermoplastic composites, substantial enhancements occur within the (5–10) wt. % FA range, but exceeding optimal ranges weakens matrix-fiber interaction, leading to diminishing returns. The article emphasizes the criticality of FA in improving the mechanical and thermodynamic characteristics of substances, specifically within the domain of composites. The investigation into FA nanoparticles, including their processing techniques and surface treatments, unveils encouraging prospects for enhancing material characteristics.

The Effect of Adding Banana Fibers on the Physical and Mechanical Properties of Mortar for Paving Block Applications

Paving blocks might encounter diverse environmental conditions during their lifespan. The durability of paving blocks is determined by their capacity to endure various exposure conditions. Synthetic fibers have been used in mortar and concrete to improve their properties. This research investigates the influence of including banana fiber (BF) on the physical and mechanical characteristics of mortar. Five different mortar mixes were developed, with varying amounts of BF ranging from 0 to 2% by volume. Testing included ultrasonic pulse velocity, compressive strength, flexural strength, total water absorption, and sorptivity. Specimens were cured for up to 90 days. The results indicate that using 0.5% BF resulted in an improvement in compressive and flexural strength compared to the control mix. There was an increase in total water absorption and the water absorption coefficient in the presence of fibers. There appeared to be good correlations between the compressive strength and the other properties examined.

Effect of pore structure characteristics on the properties of red mud-based alkali-activated cementitious materials

This study used a mercury intrusion porosimeter (MIP) to establish a Menger sponge model and a thermodynamic fractal model to investigate the influence mechanism of changes in the pore structure of red mud-based alkali-activated cementitious materials under different Na2O contents on their mechanical properties and volume stability. The results indicate that the thermodynamic fractal model can better reflect the pore size distribution within the entire pore size measurement range, with a correlation coefficient R 2 maintained between 0.98347 and 0.99854. Moreover, the thermodynamic fractal model can well reflect the relationship between the pore structure characteristics of the matrix and its macroscopic properties, with the increase of Na2O content, the N-(C)-A-S-H gel content continuously increased, and the pore fractal dimension increased from 2.42609 to 2.72440, indicating a denser pore structure, which promoted the improvement of compressive and flexural strength of the matrix at 28 days while deteriorating volume stability.

Effect of Hybrid Nanofillers on the Mechanical Characteristics of Polymethyl Methacrylate Denture Base Composite

The research study focused on enhancing the mechanical characteristics of polymethyl methacrylate (PMMA) denture bases. PMMA is commonly used in dentistry due to its easy fabrication, cost-effectiveness, and favourable physical properties. However, its limitations include low wear resistance, hardness, and mechanical strength, making it less suitable for long-term dental applications. To address these limitations, the study employed a combination of hybrid nano-fillers, specifically HNTs (halloysite nanotubes) and MWCNTs (multi-walled carbon nanotubes), at varying loading levels to improve the mechanical characteristics of the PMMA composite. These nano-fillers underwent treatment by using a coupling agent to enhance their compatibility with PMMA. Key findings of the research include that introducing HNTs/MWCNTs into the PMMA matrix led to a substantial increase in flexural strength, with a significant improvement of 109.1 MPa compared to unfilled PMMA. This indicates that the composite material became more resistant to bending or deformation. There was a substantial rise in flexural modulus values, suggesting improved stiffness in the nanocomposite compared to unfilled PMMA. In addition, the tensile strength of the PMMA composite increased by 64.4 MPa with the addition of the hybrid nano-fillers, indicating enhanced resistance to stretching or pulling forces. The study found that the improvement in flexural and tensile strength was dependent on the concentration of MWCNTs. Increasing the MWCNT concentration up to 0.75 wt.% led to improved mechanical properties, but further increases resulted in a reduction in PMMA properties. Although there was a modest improvement in Vickers hardness (approximately 18.93 kg/mm&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;), the addition of HNTs/MWCNTs as hybrid nano-fillers effectively enhanced the properties of the PMMA nanocomposite. The study concludes that incorporating hybrid nano-fillers into PMMA could contribute to the longevity and durability of dental composites, addressing some of the material&amp;apos;s inherent limitations. The specific combination and concentration of nano-fillers played a crucial role in determining the mechanical properties of the resulting nanocomposite.

Fracture mechanism and ductility performances of fiber reinforced shotcrete under flexural loading insights from digital image correlation (DIC)

This paper investigates the fracture mechanism and ductility performance of fiber-reinforced shotcrete (FRS) under flexural loading through digital image correlation (DIC) analysis. The focus is on determining the optimal mix design, utilizing recycled and manufactured fibers in shotcrete through four-point bending tests. These tests reveal significant improvements in flexural strength and ductility, as well as crack resistance, attributed to the synergistic effect of both types of fiber in hybrid fiber reinforcement. Notably, the inclusion of recycled fibers from automobile tires enhances mechanical characteristics and impact resistance, contributing to environmental sustainability and cost reduction. DIC analysis offers crucial insights into crack initiation and propagation in shotcrete, highlighting the impact of fiber reinforcement on crack patterns. Manufactured fibers delay crack onset effectively, while hybridization enhances fracture characteristics, offering improved crack control and flexural strength. The study underscores the potential of hybrid fiber mixes for enhancing structural performance in tunnel support applications, emphasizing the synergistic effect of hybrid of different fiber types. Overall, the research contributes to advancing understanding of fracture behavior in fiber-reinforced shotcrete and provides practical insights for optimizing mix designs to achieve superior mechanical properties and durability.

Modeling for predicting and optimizing of the flexural and hardness properties of jute/kenaf/glass fiber nano-composite through RSM

The research involves developing and evaluating hybrid natural and synthetic fiber composites using a hand lay-up technique and statistical analysis of variance (ANOVA) to exploit the exceptional properties of the materials. The study examines the effects of different fibers (kenaf, jute, and glass), fiber orientation, fiber sequencing, and nanoparticle content on key mechanical properties such as flexural strength and hardness. Response surface methodology (RSM) is employed to create mathematical models of these properties. Statistical analysis reveals that fiber alignment and placement have a significant impact on the mechanical properties, with the type of nanoparticles used also playing a critical role in enhancing composite strength. Composites with fibers oriented at 90° show the best mechanical properties, especially when 5 % nanoparticles by weight are added. Among the different sequences tested, the hybrid composite with a 90-degree fiber orientation, sequence 1, and 5 % nanoparticles exhibits a 40 % increase in flexural strength and a 20 % increase in hardness compared to previous designs. Sequence 2 results in a 35 % improvement in flexural strength and an 18 % increase in hardness, while sequence 3 yields a 27 % improvement in flexural strength and an 18 % increase in hardness. These results confirm the superior performance of the hybrid composites when optimized with appropriate fiber orientation, sequencing, and nanoparticle content.

Enhanced Mechanical Properties of Ceramic Rod-Reinforced TWIP Steel Composites: Fabrication, Microstructural Analysis, and Heat Treatment Evaluation

This study investigates the development and characterization of ceramic rod-reinforced TWIP (twinning-induced plasticity) steel matrix composites, produced using the lost foam casting technique. Mechanical tests revealed a substantial improvement in both flexural strength and ductility, with the composite demonstrating more than double the strength of unreinforced TWIP steel. Furthermore, a simple low-temperature heat treatment further enhanced these properties, increasing the flexural strength of the composite to 1023 MPa while also improving its ductility. The improvement in mechanical performance is attributed to the formation of additional twins in the TWIP steel matrix during deformation following heat treatment, which resulted in further strengthening of the matrix.

Tasar silk fiber waste reinforced polylactic acid composite: Physical, mechanical, and sliding wear characterization

Incorporating natural industrial waste as a reinforcement for the development of sustainable composite is now being extensively practiced to eliminate harmful synthetic fiber. This study exhaustively evaluated the potential of tasar silk fiber waste (TSFW) as a reinforcing agent in a polylactic acid (PLA) matrix to optimize the physical, mechanical, and wear properties. Therefore, PLA-based biocomposites with varying TSFW proportions (0, 2, 4, 6, 8, and 10 by weight) are manufactured and then evaluated for physical (density, voids, water absorption), mechanical (tensile, flexural, impact, and hardness), and sliding wear properties. Results suggested that water uptake of PLA composites increases with the addition of TSFW and becomes saturated after nine days of immersion. The TSFW reinforcement at 8 wt% in PLA yields 32 % and 22 % improvement in tensile strength (66.2 MPa) and flexural strength (103.2 MPa), respectively. A remarkable improvement was observed in the impact strength at similar reinforcement (8 wt%) of TSFW with the observed value of 27.90 kJ/m2. A continuous increase in hardness was obtained by including TSFW in PLA, with the highest value of 86 Shore D recorded for 10 wt% TSFW added biocomposite. The specific wear rate of all samples increased, but the incorporation of TSFW significantly reduced the same. Microscopic examination suggests that microploughing, microcutting and groove formations were the main mechanism of material removal. After examining the results, it is recommended that TSFW be used in bidirectional mat form for further enhancement of mechanical properties and improved bonding between fiber and matrix.

Bio-based liquid crystal epoxy resins: Toughening and strengthening of conventional epoxy resins with strategically extended spacer layers

Liquid crystal epoxy resin, as an ideal toughening agent, combines the features of liquid crystal ordering and network cross-linking, which can effectively optimize the comprehensive performance of blended epoxy resins and achieve an ideal balance of rigidity and toughness. Here we successfully synthesized rigid and flexible bio-based liquid crystal epoxy resin (THBR-EP) by finely tuning the length of alkyl side chains. Using aromatic diamine as curing agent, a homogeneous network without phase separation was constructed by taking advantage of the different activity but good compatibility with ordinary epoxy resins, which significantly improved the toughness of the blended system. Specifically, only a small amount of THBR-EP(2.5 wt%) was required to exhibit a maximum impact strength of 48.8 kJ/m2. Moreover, the increase in system toughness was accompanied by a benign improvement in flexural strength, modulus and thermal stability. The ordered structure of the liquid crystals and their good compatibility with the resin matrix enhanced the ability to inhibit crack extension and energy dissipation. The feasibility to simultaneously achieve effective toughening and other property improvements of common resins broadens the application of resins under various demanding scenarios.

Key Mechanical and Durability Characteristics of Concrete Admixed with Natural Rubber Latex and Sisal Fibre

Objectives: Significant infrastructure projects may require the use of high-performance concrete that possesses specific characteristics, including exceptional flexural strength, hardness, impact resistance and long-lasting durability. Polymer modified concrete is such type of concrete which improves the flexural strength and serviceability requirement of concrete buildings. Methods: The purpose of this study is to determine whether Natural Rubber Latex (NRL), a natural polymer, can replace synthetic latex and enhance the performance properties of concrete. Concrete is enhanced by the inclusion of natural rubber latex, which contributes a dry rubber content ranging from 0.5% to 1.5% of the weight of cement in the mixed composition. This study examines and compares the characteristics of latex modified concrete with sisal fibre-reinforced concrete with a constant sisal fibre content of 0.3%. It also investigates the combined effect of fibre and latex in concrete. Findings: The findings demonstrated a substantial enhancement in the ability of concrete to absorb energy (up to 166%) under impact loading. Additionally, the modification of concrete using latex resulted in an improvement in flexural strength of up to 39%. The decreased permeability of chloride ions and reduced water absorption in latex treated concrete are clear indications of its exceptional durability. Novelty: Polymer modified concrete using NRL is the next generation concrete and the sisal fibre incorporation in it is a relatively a novel approach in the field of concrete technology. It encourages the advancement of eco-friendly technology in the construction industry. Keywords: Sisal Fibre, Impact resistance, Chloride permeability, Natural rubber latex, Water absorption

Enhancement of sintering and mechanical properties of alumina-rich Al2O3-MgO-CaO refractory composite by doping La2O3

Ceramics or refractories prepared in the Al2O3-rich corner of the Al2O3-MgO-CaO system show excellent high-temperature mechanical properties and chemical stability because of the presence of spinel (MgAl2O4) and calcium hexaluminate (CaAl12O19). However, the densification of these two crystals usually requires high firing temperatures due to their poor sinterability. To address this issue, La2O3-doped MgAl2O4-CaAl4O7-CaAl12O19 refractory composites were designed, and the influence of the doping level on the densification, microstructure, and mechanical properties of the composite was investigated. It was found that the doped La3+ was predominantly dissolved in the CA6 grains by replacing Ca2+, forming uniform solid solutions regardless of doping concentration. This reaction significantly accelerates ion diffusion and CA2 grain growth. Besides, it reduces the aspect ratio of CA6 crystals, weakening the negative effect of the elongated grains on mass transfer and sintering. As a result, the relative density increases from 79.5 % to 95.1 % after sintering at 1600 °C with doping only 0.5 wt% La2O3 into the composite, producing a uniform and dense microstructure with regular angular grains. The above effects result in a significant improvement in flexural strength and fracture toughness (increasing by 61 % and 57 %, respectively). Moreover, the La2O3-doped refractory composite achieves a decline of the high-temperature creep rate by one order of magnitude at 1600 °C.

Mechanical properties and damage modeling of hybrid fiber reinforced concrete under freeze-thaw cycles

This study aimed to investigate the mechanical properties of steel-polyacrylonitrile hybrid fiber reinforced concrete and its durability under freeze-thaw damage. Firstly, the mechanical properties of hybrid fiber reinforced concrete were studied by compressive strength and flexural strength tests. Secondly, with the help of rapid freeze-thaw test, the variation rules of mass loss rate and relative dynamic elastic modulus were characterized. Based on the test results and freeze-thaw damage theory, the evolution equation of freeze-thaw damage of hybrid fiber reinforced concrete based on Weibull distribution was established. The results show that the enhancement effect of hybrid fiber on the mechanical strength of concrete is better than that of single mixed fiber, especially in the improvement of flexural strength; Accordingly, compared with the single mixing of steel fibers or single mixing of polyacrylonitrile fibers, hybrid fibers are more effective in improving the durability of concrete against freezing and this improvement effect increases with the increase of steel fiber content; The freeze-thaw damage model of Weibull distribution can better reflect the freeze-thaw damage process of hybrid fiber reinforced concrete .Through the freeze-thaw damage evolution curve, it can be found that after 500 freeze-thaw cycles, the freeze-thaw damage degree of the hybrid fiber reinforced concrete with different steel fiber content has been very close, which means that the influence of steel fiber content on the freeze-resistant performance of hybrid fiber reinforced concrete will be limited. This study provides a theoretical basis and technical basis for the design of concrete structures in alpine regions.

Enhancing interfacial performance and fracture toughness of carbon fibre reinforced thermoplastic composites

Enhancing the interlaminar fracture toughness of composites significantly improves their load bearing capacity and structural integrity over longer service life by improving their resistance to delamination. The effect of hybrid toughening of Elium-based thermoplastic composites involving polydopamine (PDA), multi-walled carbon nanotubes (MWCNTs) sizing, and polyphenylene sulfide (PPS) veil interlayers was investigated to observe the mechanical response using 3-point bending, interlaminar shear strength, and Mode I fracture toughness tests. The enhancement of fibre–matrix adhesion contributed to improvements in both flexural strength and interlaminar shear strength, while additional toughening mechanisms, such as PDA bridging, PPS pull-out and breakage, and fibre bridging, enhanced the Mode I interlaminar fracture toughness by 218%.