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In recent years, an emerging technology termed, “High-Performance Fiber-Reinforced Concrete (HPFRC)” has become popular in the construction industry. The materials used in HPFRC depend on the desired characteristics and the availability of suitable local economic alternative materials. Concrete is a common building material, generally weak in tension, often ridden with cracks due to plastic and drying shrinkage. The introduction of short discrete fibers into the concrete can be used to counteract and prevent the propagation of cracks. Despite an increase in interest to use HPFRC in concrete structures, some doubts still remain regarding the effect of fibers on the properties of concrete. This paper presents the most comprehensive review to date on the mechanical, physical, and durability-related features of concrete. Specifically, this literature review aims to provide a comprehensive review of the mechanism of crack formation and propagation, compressive strength, modulus of elasticity, stress–strain behavior, tensile strength (TS), flexural strength, drying shrinkage, creep, electrical resistance, and chloride migration resistance of HPFRC. In general, the addition of fibers in high-performance concrete has been proven to improve the mechanical properties of concrete, particularly the TS, flexural strength, and ductility performance. Furthermore, incorporation of fibers in concrete results in reductions in the shrinkage and creep deformations of concrete. However, it has been shown that fibers may also have negative effects on some properties of concrete, such as the workability, which get reduced with the addition of steel fibers. The addition of fibers, particularly steel fibers, due to their conductivity leads to a significant reduction in the electrical resistivity of the concrete, and it also results in some reduction in the chloride penetration resistance of the concrete.

In this study, the effect of waste glass on the mechanical properties of concrete was examined by conducting a series of compressive strength, splitting tensile strength and flexural strength tests. According to this aim, waste glass powder (WGP) was first used as a partial replacement for cement and six different ratios of WGP were utilized in concrete production: 0%, 10%, 20%, 30%, 40%, and 50%. To examine the combined effect of different ratios of WGP on concrete performance, mixed samples (10%, 20%, 30%) were then prepared by replacing cement, and fine and coarse aggregates with both WGP and crashed glass particles. Workability and slump values of concrete produced with different amounts of waste glass were determined on the fresh state of concrete, and these properties were compared with those of plain concrete. For the hardened concrete, 150 mm × 150 mm × 150 mm cubic specimens and cylindrical specimens with a diameter of 100 mm and a height of 200 mm were tested to identify the compressive strength and splitting tensile strength of the concrete produced with waste glass. Next, a three-point bending test was carried out on samples with dimensions of 100 × 100 × 400 mm, and a span length of 300 mm to obtain the flexure behavior of different mixtures. According to the results obtained, a 20% substitution of WGP as cement can be considered the optimum dose. On the other hand, for concrete produced with combined WGP and crashed glass particles, mechanical properties increased up to a certain limit and then decreased owing to poor workability. Thus, 10% can be considered the optimum replacement level, as combined waste glass shows considerably higher strength and better workability properties. Furthermore, scanning electron microscope (SEM) analysis was performed to investigate the microstructure of the composition. Good adhesion was observed between the waste glass and cementitious concrete. Lastly, practical empirical equations have been developed to determine the compressive strength, splitting tensile strength, and flexure strength of concrete with different amounts of waste glass. Instead of conducting an experiment, these strength values of the concrete produced with glass powder can be easily estimated at the design stage with the help of proposed expressions.

Load bearing/energy storage integrated devices (LEIDs) allow using structural parts to store energy, and thus become a promising solution to boost the overall energy density of mobile energy storage systems, such as electric cars and drones. Herein, with a new high-strength solid electrolyte, we prepare a practical high-performance load-bearing/energy storage integrated electrochemical capacitors with excellent mechanical strength (flexural modulus: 18.1 GPa, flexural strength: 160.0 MPa) and high energy storage ability (specific capacitance: 32.4 mF cm −2 , energy density: 0.13 Wh m −2 , maximum power density: 1.3 W m −2 ). We design and compare two basic types of multilayered structures for LEID, which significantly enhance the practical bearing ability and working flexibility of the device. Besides, we also demonstrate the excellent processability of the LEID, by forming them into curved shapes, and secondarily machining and assembling them into complex structures without affecting their energy storage ability. High-strength composite materials for electrochemical energy storage is attractive for mobile systems. Here the authors demonstrate high-performance load-bearing integrated electrochemical capacitors, which show high strength, large capacitance, and good machinability.

The current research proposes a novel method for printing continuous carbon fiber composite parts. At first, continuous carbon fiber prepreg filament for Fused Deposition Modeling 3D printing was manufactured, followed by modification of extruder head of 3D printers to print the filament. Thereafter, three-point flexural test and Response Surface Methodology were adopted to study the mechanical properties of the composite parts printed with the filament. After testing, a mathematical model was developed to describe and analyze the relationship between the printing parameters (printing temperature, printing speed, and layer thickness) and the flexural strength of printed composite parts. We discovered that the flexural strength and flexural modulus of printed composites significantly improved with the proposed method with specified printing parameters, and while of all the parameters, the layer thickness had the greatest contribution towards the final flexural strength. The results indicate that the discussed method could be a promising approach to print CCF composites.

Background. Recently, dentists can utilize three-dimensional printing technology in fabricating dental restoration. However, to date, there is a lack of evidence regarding the effect of printing layer thicknesses and postprinting on the mechanical properties of the 3D-printed temporary restorations with the additive manufacturing technique. So, this study evaluated the mechanical properties of a 3D-printed dental resin material with different printing layer thicknesses and postprinting methods. Methods. 210 specimens of a temporary crown material (A2 EVERES TEMPORARY, SISMA, Italy) were 3D-printed with different printing layer thicknesses (25, 50, and 100 μm). Then, specimens were 3D-printed using DLP technology (EVERES ZERO, DLP 3D printer, SISMA, Italy) which received seven different treatment conditions after printing: water storage for 24 h or 1 month, light curing or heat curing for 5 or 15 minutes, and control. Flexural properties were evaluated using a three-point bending test on a universal testing machine (ISO standard 4049). The Vickers hardness test was used to evaluate the microhardness of the material system. The degree of conversion was measured using an FT-IR ATR spectrophotometer. Statistical analysis was performed using two-way analysis of variance (ANOVA) and Tukey’s honestly significant difference (HSD) test (p≤0.05). Results. The 100 μm printing layer thickness had the highest flexural strength among the other thickness groups. As a combined effect printing thickness and postprinting conditions, the 100 μm with the dry storage group has the highest flexural strength among the tested groups (94.60 MPa). Thus, the group with 100 μm thickness that was heat cured for 5 minutes (HC 5 min 100 μm) has the highest VHN value (VHN=17.95). Also, the highest mean DC% was reported by 50 μm layer thickness (42.84%).Conclusions. The thickness of the 100 μm printing layer had the highest flexural strength compared to the 25 μm and 50 μm groups. Also, the postprinting treatment conditions influenced the flexural strength and hardness of the 3D-printed resin material.

Nanocomposites of epoxy with 3 and 5 wt% graphene nanoplatelets (GnPs) were fabricated with GnP sizes of ~5 and <1 μm dispersed within an epoxy resin using a sonication process followed by three-roll milling. The morphology, mechanical, and thermal properties of the composites were investigated. Tensile and flexural properties measurements of these nanocomposites indicated higher modulus and strength with increasing concentration of small GnPs sizes (<1 μm, GnP-C750). The incorporation of larger GnPs sizes (~5 μm, GnP-5) significantly improved the tensile and flexural modulus but reduced the strength of the resulting composites. At 35 °C, the dynamic storage modulus of GnP-5/epoxy composites increased with increasing platelet concentration, and improved by 12 % at 3 wt% and 23 % at 5 wt%. The smaller GnP-C750 increased the storage modulus by 5 % at 3 wt% loading but only 2 % at 5 wt% loading. The glass transition temperatures of the composites increased with increasing platelet concentration regardless of the GnP particle size. A marked improvement in thermal conductivity was measured with the incorporation of the larger GnP size reaching 115 % at 5 wt% loading. The effects of different platelet sizes of the GnP reinforcement on the damage mechanisms of these nanocomposites were studied by scanning electron microscopy.

One of the major challenges in off-shore tidal and wave energy devices is the ageing of these structures in the hostile marine environment, which limits their operating life. In this research, mechanical properties of aged glass/epoxy and carbon/epoxy composite specimens including tensile strength, Young’s modulus, flexural strength, and shear strength, following immersion in a representative accelerated marine degradation environment (artificial seawater, with 3.5% salinity at room temperature and 60 °C) have been investigated. The microstructure and physicochemical characterization of the aged samples were assessed via microscopic imaging, micro-CT scanning and differential scanning calorimetry. The degradation phenomenon was apparent in the change of mechanical properties and microstructure of composite laminates (micro-cracks and debonding between matrix and fibre). Generally, the ageing process had a more severe effect on tensile and shear strengths of glass/epoxy samples than those of carbon/epoxy specimens. Reversely, the results of bending tests of carbon/epoxy composites showed more drop-in flexural properties than glass/epoxy samples. The results revealed that degradation mechanisms continue even after reaching the saturation point in composite materials. The achievements of this research present a good understanding of the effect of degradation of composite materials in salt water to deal with their application in real service environment.

Single-shade universal resin composites (SsURC) are preferred in clinical practice to reduce time for shade selection and obtain good esthetic results. In this study, the static mechanical properties of seven new SsURCs were investigated, their spectral analyzes were performed and scanning electron microscopy (SEM) evaluations were presented. Charisma Diamond One/DO, Admira Fusion x-tra/AFX, Omnichroma/OC, OptiShade/OS, Essentia Universal/EU, Zenchroma/ZC, Vittra APS Unique/VU were used in a three-point bending test to determine flexural strength (FS) and elastic modulus (EM); Vickers micro-hardness (VHN) and hardness-ratio (HR) were performed with a micro-hardness tester from top/bottom after 24-h/15-days of storage in distilled water at 37 °C (±1 °C). The degree of conversion (DC) was assessed by using Fourier transform infrared spectroscopy (FTIR). The structure of the resin matrix and filler content were assessed by SEM. Data were analyzed using IBM SPSS V23 and the R program and the significance level was taken as p < 0.05. The main effect of the tested SsURCs was found to be statistically significant on FS, EM, VHN, and DC values (p < 0.001). Bis-GMA free SsURCs (AFX, DO, VU) showed better DC and HR except for OC. All seven tested SsURCs conform to the requirements of ISO standards for dental resin composites for all tested categories.

In this study, biodegradable biocomposites based on polylactide with basalt fibres (BFs) or wood fibres (WFs) of 7.5 or 15 wt% were prepared by injection moulding. Various tests, including tensile test, bending test and impact test, were carried out to investigate the mechanical properties of the composites. Additionally, the samples were tested at different temperatures. Depending on the type of fibre, differences were noted in their mechanical properties; the addition of WF caused a decrease in strength and the higher the fibre content, the higher the decrease was noted from 18% up 25% in the case of tensile strength. However, the Young modulus was improved by 45% for composites with 15 wt% of WF. The addition of BF improved all the properties, especially Young modulus was improved by over 45%. Despite the low strength observed in neat polylactide at high temperatures-394 MPa, the addition of WF or BF improved the flexural strength more than twofold up to 1684 MPa (PLA/15BF). Moreover, the addition of natural fibres caused an increase in dimensional stability as shown by the decrease of the coefficient of thermal expansion which dropped over 50% for composites with 15 wt% of BF, which significantly expands the areas of use of materials. After 4 weeks of biodegradation, only a slight decrease approximately 5% was observed in the mechanical properties together with an increase in crystallinity. Overall, the results confirm that the prepared composites can be successfully used in engineering applications with long-term operation.

The utilization of solid waste in useful product is becoming a great deal of worth for individuals, organizations, and countries themselves. The powder of waste glass and silica fumes are also considered major waste materials across the globe. In this paper, the physico-chemical, thermal, and morphological properties of both waste powders are investigated in order to determine their suitability for use as a partial replacement for cement in basic concrete. They are suitable for use in concrete due to their pozzolanic and other basic properties. Extensive testing, in terms of the compressive strength test, the slump test, and the flexural strength test, has been carried out to study the replacement of cement in the range of 5–15% by waste glass powder for curing ages of 7 and 28 days. The FTIR analyses of both materials are studied for determining the effect of characteristics of chemical bonding and intense bands with bending vibrations of O–Si–O bonds. Experimental results indicate towards the potential utilization of wastes in concrete in terms of green concrete.