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This work represents a study to investigate the mechanical properties of longitudinal basalt/woven-glass-fiber-reinforced unsaturated polyester-resin hybrid composites. The hybridization of basalt and glass fiber enhanced the mechanical properties of hybrid composites. The unsaturated polyester resin (UP), basalt (B) and glass fibers (GF) were fabricated using the hand lay-up method in six formulations (UP, GF, B7.5/G22.5, B15/G15, B22.5/G7.5 and B) to produce the composites, respectively. This study showed that the addition of basalt to glass-fiber-reinforced unsaturated polyester resin increased its density, tensile and flexural properties. The tensile strength of the B22.5/G7.5 hybrid composites increased by 213.92 MPa compared to neat UP, which was 8.14 MPa. Scanning electron microscopy analysis was used to observe the fracture mode and fiber pullout of the hybrid composites.

Fiber-reinforced polymer composites, reaching a production of approximately 2.56 million tons in 2023 in Europe, display unique properties, yet they are disposed of at their end of service by conventional methods such as landfill and incineration. Here, we review the recycling of fiber-reinforced polymer wastes in the construction industry, with emphasis on fiber-reinforced polymer composites, recycling methods, and applications of carbon and glass fiber polymer composites in civil engineering. Recycling methods include mechanical, thermal, and chemical techniques. Applications comprise the use in fine fillers, coarse and fine aggregates, macro-fibers, alkali-activated materials, geopolymers, asphalt composites, and cement composites. We discuss workability, mechanical properties including compressive, flexural and tensile properties, durability, and surface modification. Future applications include three-dimensional concrete printing, self-sensing cement composites, self-heating and energy harvesting cement composites, and electromagnetic shielding. We propose a waste management hierarchy, considering the source of composites and their intended applications, to improve circularity.

Prior studies in the literature show promising results regarding the improvements in strength and durability of concrete upon incorporation of glass fibers into concrete formulations. However, the knowledge regarding glass fiber usage in concrete is scattered. Moreover, this makes it challenging to understand the behavior of glass fiber-reinforced concrete. Therefore, a detailed review is required on glass fiber-reinforced concrete. This paper provides a compressive analysis of glass fiber-reinforced composites. All-important properties of concrete such as flowability, compressive, flexural, tensile strength and modulus of elasticity were presented in this review article. Furthermore, durability aspects such as chloride ion penetration, water absorption, ultrasonic pulse velocity (UPV) and acid resistance were also considered. Finally, the bond strength of the fiber and cement paste was examined via scanning electron microscopy. Results indicate that glass fibers improved concrete’s strength and durability but decreased the concrete’s flowability. Higher glass fiber doses slightly decreased the mechanical performance of concrete due to lack of workability. The typical optimum dose is recommended at 2.0%. However, a higher dose of plasticizer was recommended for a higher dose of glass fiber (beyond 2.0%). The review also identifies research gaps that should be addressed in future studies.

The growing use of carbon and glass fibres has increased awareness about their waste disposal methods. Tonnes of composite waste containing valuable carbon fibres and glass fibres have been cumulating every year from various applications. These composite wastes must be cost-effectively recycled without causing negative environmental impact. This review article presents an overview of the existing methods to recycle the cumulating composite wastes containing carbon fibre and glass fibre, with emphasis on fibre recovery and understanding their retained properties. Carbon and glass fibres are assessed via focused topics, each related to a specific treatment method: mechanical recycling; thermal recycling, including fluidised bed and pyrolysis; chemical recycling and solvolysis using critical conditions. Additionally, a brief analysis of their environmental and economic aspects are discussed, prioritising the methods based on sustainable values. Finally, research gaps are identified to highlight the factors of circular economy and its significant role in closing the life-cycle loop of these valuable fibres into re-manufactured composites.

The inherent brittleness of glass-fiber-reinforced polymer (GFRP) bars limits their structural applicability despite their corrosion resistance and lightweight properties. This study addresses the critical challenge of enhancing the ductility and crack resistance of GFRP-reinforced systems while maintaining their environmental resilience. Through experimental evaluation, GFRC slabs reinforced with GFRP bars are systematically compared to steel-reinforced GFRC slabs and non-bar-reinforced SFRC slabs under bending loads. Eight slabs were subjected to four-edge-supported loading following standardized procedures based on prior strength assessments. The results demonstrate that GFRP-reinforced GFRC slabs achieve an ultimate load capacity of 83.7 kN, comparable to their steel-reinforced counterparts (96.3 kN), while exhibiting progressive crack propagation and 17% higher energy absorption than non-fiber-reinforced systems. The load capacity similarities between GFRP-bar-reinforced GFRC slabs and steel-reinforced slabs are 69% for crack loading and 86% for ultimate capacity. Furthermore, this study demonstrates that the reduction factor in flexural strength design of the novel slab should be comprehensively considered, incorporating the recommended value of 0.5. The findings confirm that GFRP-bar-reinforced GFRC slabs meet key structural performance criteria, including enhanced bending capacity, energy absorption, crack resistance, and ductility. This study underscores the potential of GFRP as an effective alternative to steel reinforcement, contributing to the development of resilient and durable concrete structures in demanding environments.

Thermoplastic pultrusion is a suitable process for fabricating continuous unidirectional thermoplastics with a uniform cross-section, high mechanical properties due to continuous fiber reinforcement, low cost, and suitability for mass production. In this paper, jute and glass fibers were reinforced with a polypropylene matrix and fabricated using the thermoplastic pultrusion process. The volumetric fraction of the composite was designed by controlling the filling ratio of the reinforcing fiber and matrix. The effects of molding parameters were investigated, such as pulling speed and molding temperature, on the mechanical properties and microstructure of the final rectangular profile composite. The pulling speed and molding temperature varied from 40 to 140 mm/min and 190 to 220 °C, respectively. The results showed that an increase in molding temperature initially led to an increase in mechanical properties, up to a certain point. Beyond that point, they started to decrease. The resin can be easily impregnated into the fiber due to the low viscosity of thermoplastic at high temperatures, resulting in increased mechanical properties. However, the increase in molding temperature also led to a rise in void content due to moisture in jute fiber, resulting in decreased mechanical properties at 210 °C. Meanwhile, un-impregnation decreased with the increase in molding temperature, and the jute fiber began to degrade at high temperatures. In the next step, with varying pulling speed, the mechanical properties decreased as the pulling speed increased, with a corresponding increase in void content and un-impregnation. This effect occurred because the resin had a shorter time to impregnate the fiber at a higher pulling speed. The decrease in mechanical properties was influenced by the increase in void content and un-impregnation, as the jute fiber degraded at higher temperatures.

Utilizing fibre-reinforced concrete is still a difficulty for present engineers. Generally, it is acknowledged that the mechanical, cracking and fracture qualities of fibre-reinforced concrete are much better than those of conventional concrete. The addition of fibres to the concrete matrix mitigates its fragility. Typically, short fibres are utilised in concrete to prevent cracks caused by drying and autogenous shrinkage. Currently, there is a substantial increase in the use of short alkali-resistant glass fibres. This experiment was conducted to examine the influence of glass fibre reinforcement on the compressive and flexural behaviour of concrete. This research investigates the characteristics of glass fibres reinforced concrete (GFRC) after 7 and 28 days of curing, such that GFRC may be employed in construction. Concrete containing short alkali-resistant glass fibres of 36 mm in length and 1% volume fraction (VF) was developed for this purpose. The testing findings revealed that the average compressive strength of GFRC after 28 days of curing was 72.06 MPa. The flexural properties of GFRC are determined, and the 7-day and 28-day average bending strengths of GFRC concrete samples are 6.46 MPa and 7.94 MPa, respectively, indicating that GFRC responds well under loading conditions.

This research aims to examine the fracture toughness of hybrid fibrous geopolymer composites under mode II. For this purpose, eight geopolymer mixtures were cast and tested to evaluate the influence of steel and synthetic fiber hybridization on mode II fracture response. The first mixture was plain and was kept as a reference, while steel, polypropylene and glass fibers were used in the rest seven mixtures. The first three of which were mono-reinforced with one of the three fibers, while the rest of the four were hybrids reinforced with combinations of steel and synthetic fibers. The Brazilian center notched disc and the double notched cube test configurations were used to evaluate the mode II fracture toughness of the eight mixtures. The results of the tests showed that steel fibers played the vital role in enhancing the fracture toughness, where the mixtures S1.6 and S1.3G0.3 showed the best performance. The results also showed that increasing the notch depth decreased the fracture toughness with an approximate linear decrement fashion. It was found that the use of double-notched cubes resulted in much higher fracture toughness than the Brazilian notched discs, where the ratio of normalized fracture toughness of the disc specimens to cube specimens was approximately 0.37 to 0.47. This is attributed to the concentration of stresses along one defined path in the disc specimens compared to the multi-path stresses in the cube specimens. In addition, the accompanied tensile stresses in the disc specimens may lead to a mode I fracture before the designed mode II fracture.

PurposeMore than 2 billion tons of construction waste soil are generated every year in China, leading to waste and degradation of land resources. This study aims to develop a reinforcement technology for granite residual soil, the common type of construction waste in China, evaluate the reinforcement properties, and investigate the mechanism.MethodIn this study, the polymer SH, glass fiber, and granite residual soils were mechanically mixed to prepare specimens for impact resistance tests. Additionally, the specimens obtained were characterized using a combination of techniques including X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM).ResultsThe low-velocity impact test showed that the impact resistance of granite residual soil is highly related to the content of SH. When the content reaches 3.5%, the impact resistance is the best. Results of characterization revealed that kaolinite plays an important role in the reinforcement system, which can be summarized into the following: (1) the hydrophobic group (C–C) on the SH molecular chain is bridged on the surface of kaolinite, transforming kaolinite from hydrophilic to hydrophobic; thus, the disintegration characteristic of GRS in water was moderated. (2) The pores between kaolinite are also filled by SH molecular chains. (3) In particular, the frictional engagement of kaolinite and glass fiber also enables the tensile strength of glass fiber to be exerted.ConclusionThese findings provide possibilities for the effective recycling of granite residual soil on a vast scale and the sustainable development of construction waste soils.

This work investigates the effects of fibre content, fibre orientation, and frequency on the dynamic behaviour of flax fibre-reinforced polypropylene composites (FFPCs) to improve understanding of the parameters affecting vibration damping in FFPCs. The effects of fibre content and fibre orientation on the mechanical performances of FFPCs, along with fracture characteristics, are also investigated in this study. Laminates of various fibre contents and orientations were manufactured by a vacuum bagging process, and their dynamic and static properties were then obtained using dynamic (dynamic mechanical analysis (DMA) to frequencies of 100 Hz) and various mechanical (tensile and flexural) analyses, respectively. The findings suggest that of all the parameters, fibre orientation has the most significant impact on the damping, and the maximum loss factor (i.e., 4.3–5.5%) is obtained for 45° and 60° fibre orientations. However, there is no significant difference in loss factors among the composites with different fibre contents. The loss factors lie mainly in the range of 4–5.5%, irrespective of the fibre volume fraction, fibre orientation, and frequency. A significant improvement (281 to 953%) in damping is feasible in flax fibre/polypropylene composites relative to more widespread glass/epoxy composites. The mechanical properties of composites are also strongly affected by fibre orientation with respect to the loading direction; for example, the tensile modulus decreases from 20 GPa to 3.45 GPa at an off-axis angle of 30° for a fibre volume fraction of 0.40. The largest mechanical properties (tensile and flexural) are found in the case of 0° fibre orientation. For composites with fibre volume fractions in the range 0.31–0.50, tensile moduli are in the range 16–21 GPa, and tensile strengths are in the range 125–173 MPa, while flexural moduli and strengths are in the ranges 12–15 GPa and 96–121 MPa, respectively, making them suitable for structural applications. The obtained results also suggest that flax fibre composites are comparable to glass fibre composites, especially in terms of specific stiffness. The ESEM analysis confirms the tensile failures of specimens due to fibre debonding, fibre pull-out and breakage, matrix cracking, and inadequate fibre/matrix adhesion. The outcomes from this study indicate that flax fibre-reinforced composite could be a commercially viable material for applications in which noise and vibration are significant issues and where a significant amount of damping is required with a combination of high stiffness and low weight.