Search Results (78)

This study introduced basalt fibres as a reinforcing material and employed notched beam three-point bending tests combined with digital image correlation (DIC) technology to comprehensively evaluate key fracture parameters—namely, initial fracture toughness, unstable fracture toughness, fracture energy, and ductility index—of expanded polystyrene (EPS)-based geopolymer concrete with different mix proportions. The results demonstrate that the optimal fracture performance was achieved when the basalt fibre volume content was 0.4% and the EPS content was 20%, resulting in respective increases of 12.07%, 28.73%, 98.92%, and 111.27% in the above parameters. To investigate the toughening mechanisms, scanning electron microscopy was used to observe the fibre–matrix interfacial bonding and crack morphology, while X-ray micro-computed tomography enabled detailed three-dimensional visualisation of internal porosity and crack development, confirming the crack-bridging and energy-dissipating roles of basalt fibres. Furthermore, the crack propagation process was simulated using the extended finite element method, and the evolution of fracture-related parameters was quantitatively analysed using a linear superposition progressive assumption. A simplified predictive model was proposed to estimate fracture toughness and fracture energy based on the initial cracking load, peak load, and compressive strength. The findings provide theoretical support and practical guidance for the engineering application of basalt fibre-reinforced EPS-based geopolymer lightweight concrete. Full article

This paper deals with an important issue, which is the influence of failure caused by the quality of matrix post-curing on the strength of complex and difficult materials of the “new generation” such as fibre composites, particularly with a polymer matrix. In recent years, significant advances in the field of adhesive materials chemistry have led to the constant development of bonding technology. The effectiveness of bonding depends, to a large extent, on the suitable selection of the adhesive and the use of appropriate surface treatment technology. It is difficult to imagine virtually any modern industry without adhesive joints, be it the aircraft, aerospace or automotive industries, which simultaneously highlights the great importance of adhesives and adhesive materials for the present-day economy. In modern technology, it is extremely important to obtain the right combination of modern construction materials. The statistical analysis of the components showed the complexity of the layered composite structure. The proposed model of the weakest micro-volume developed in this study indirectly reflects the experimentally based curing variables that affect the stresses of the components in the composite (laminate) structure. The strength of fibrous composite structures based on the Markov chain theory considers technological aspects during hardening. The model proposed in the paper was validated on the basis of examples from the literature and experimental data obtained in the research project. The numerical results are in good agreement with the literature database and measurement data. The presented model could be a novel method, which allows better insight into the curing process of epoxy resins. Full article

At a time of climate change, farmers face difficulties in providing food for a growing population. This results in the overuse of water and fertilisers. The aim of the research was to test the possibility of introducing waste sheep wool fibres into a hydrogel to obtain a stable material that could improve water retention and could serve as a fertiliser material matrix. Wool fibres and hydrogel were chosen because of their ability to store water and their degradability. An evaluation of the swelling degree of different alginate-based hydrogel matrices was performed to select the matrix. The stability and water bonding of hydrogels with different wool fibre content were analysed and evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The microstructure and the effect of fibres on the uniformity of the hydrogel were assessed using SEM and optical microscopy. The degree of water retention in the soil was also evaluated. The results showed that it is possible to incorporate wool fibres into the hydrogel matrix and the wool fibres make the composite porous, which allows water penetration into the material much more easily. This research has shown the possibility of using waste wool fibres as an active ingredient in sustainable fertiliser materials. Full article

In the present study, a programme of experimental investigations was carried out to examine the direct uniaxial tensile (and pull-out) behaviour of plain and fibre-reinforced lightweight aggregate concrete. The lightweight aggregates were recycled from fly ash waste, also known as Pulverised Fuel Ash (PFA), which is a by-product of coal-fired electricity power stations. Steel fibres were used with different aspect ratios and hooked ends with single, double and triple bends corresponding to 3D, 4D and 5D types of DRAMIX steel fibres, respectively. Key parameters such as the concrete compressive strength f_lck, fibre volume fraction V_f, number of bends n_b, embedded length L_E and inclination angle ϴ_f were considered. The fibres were added at volume fractions V_f of 1% and 2% to cover the practical range, and a direct tensile test was carried out using a purpose-built pull-out test developed as part of the present study. Thus, the tensile mechanical properties were established, and a generic constitutive tensile stress–crack width σ-ω model for both plain and fibrous lightweight concrete was created and validated against experimental data from the present study and from previous research found in the literature (including RILEM uniaxial tests) involving different types of lightweight aggregates, concrete strengths and steel fibres. It was concluded that the higher the number of bends n_b and the higher the volume fraction V_f and concrete strength f_lck, the stronger the fibre–matrix interfacial bond and thus the more pronounced the enhancement provided by the fibres to the uniaxial tensile residual strength and ductility in the form of work and fracture energy. A fibre optimisation study was also carried out, and design recommendations are provided. Full article

Pineapple leaf fibres represent a biodegradable raw material sourced from renewable resources whose use contributes to reducing the carbon footprint and limiting the amount of waste generated. Their potential applications can effectively decrease the industry’s dependence on plastics and support sustainable development, which should accompany the production of modern materials. In this study, polyurethane-based composites reinforced with various types of natural cellulose fillers were developed and investigated. Microcrystalline cellulose and unmodified and chemically modified pineapple leaf fibres were used as reinforcements. The mechanical and thermal properties of the produced materials were determined and compared. The results of the tests indicated that both microcrystalline cellulose and pineapple leaf fibres contributed to a reduction in the mechanical properties of polyurethane. A varying impact of fillers on the Young’s modulus of the biocomposites was observed. The presence of natural modifiers influenced an increase in the melting temperature of the composite compared to the pure polyurethane. Integration of natural pineapple fibres into composite represents a step toward a more sustainable future, combining economic benefits with environmental care. The mechanical characteristics of composite materials were enhanced by modified fibres, compared to their unmodified counterparts. This improvement comes from the unique structural properties of the modified fibres. When polyurethane (PU) is used as the matrix material, it effectively fills the interfibrillar voids, creating a more cohesive bond between the components. Full article

Macroscopic structures consisting of two or more materials are called composites. The decreasing reserves of the world’s oil reserve and the environmental pollution of existing energy and production resources made the use of recycling methods inevitable. There are mechanical, thermal, and chemical recycling methods for the recycling of thermosets among composite materials. The recycling of thermoset composite materials economically saves resources and energy in the production of reinforcement and matrix materials. Due to the superior properties such as hardness, strength, lightness, corrosion resistance, design width, and the flexibility of epoxy/vinylester/polyester fibre formation composite materials combined with thermoset resin at the macro level, environmentally friendly sustainable development is happening with the increasing use of composite materials in many fields such as the maritime sector, space technology, wind energy, the manufacturing of medical devices, robot technology, the chemical industry, electrical electronic technology, the construction and building sector, the automotive sector, the defence industry, the aviation sector, the food and agriculture sector, and sports equipment manufacturing. Bonded joint studies in composite materials have generally been investigated at the level of a single composite material and single joint. The uncertainty of the long-term effects of different composite materials and environmental factors in single-lap bonded joints is an important obstacle in applications. The aim of this study is to investigate the effects of single-lap bonded GFRP (glass fibre-reinforced polymer) and CFRP (carbon fibre-reinforced polymer) specimens on the material at the end of seawater exposure. In this study, 0/90 orientation twill weave seven-ply GFRP and eight-ply CFRP composite materials were used in dry conditions (without seawater soaking) and the hand lay-up method. Seawater was taken from the Aegean Sea, İzmir province (Selçuk/Pamucak), in September at 23.5 °C. This seawater was kept in different containers in seawater for 1 month (30 days), 2 months (60 days), and 3 months (90 days) separately for GFRP and CFRP composite samples. They were cut according to ASTM D5868-01 for single-lap joint connections. Moisture retention percentages and axial impact tests were performed. Three-point bending tests were then performed according to ASTM D790. Damage to the material was examined with a ZEISS GEMINESEM 560 scanning electron microscope (SEM). The SEM was used to observe the interface properties and microstructure of the fracture surfaces of the composite samples by scanning images with a focused electron beam. Damage analysis imaging was performed on CFRP and GFRP specimens after sputtering with a gold compound. Moisture retention rates (%), axial impact tests, and three-point bending test specimens were kept in seawater with a seawater salinity of 3.3–3.7% and a seawater temperature of 23.5 °C for 1, 2, and 3 months. Moisture retention rates (%) are 0.66%, 3.43%, and 4.16% for GFRP single-lap bonded joints in a dry environment and joints kept for 1, 2, and 3 months, respectively. In CFRP single-lap bonded joints, it is 0.57%, 0.86%, and 0.87%, respectively. As a result of axial impact tests, under a 30 J impact energy level, the fracture toughness of GFRP single-lap bonded joints kept in a dry environment and seawater for 1, 2, and 3 months are 4.6%, 9.1%, 14.7%, and 11.23%, respectively. At the 30 J impact energy level, the fracture toughness values of CFRP single-lap bonded joints in a dry environment and in seawater for 1, 2, and 3 months were 4.2%, 5.3%, 6.4%, and 6.1%, respectively. As a result of three-point bending tests, GFRP single-lap joints showed a 5.94%, 8.90%, and 12.98% decrease in Young’s modulus compared to dry joints kept in seawater for 1, 2, and 3 months, respectively. CFRP single-lap joints showed that Young’s modulus decreased by 1.28%, 3.39%, and 3.74% compared to dry joints kept in seawater for 1, 2, and 3 months, respectively. Comparing the GFRP and CFRP specimens formed by a single-lap bonded connection, the moisture retention percentages of GFRP specimens and the amount of energy absorbed in axial impact tests increased with the soaking time in seawater, while Young’s modulus was less in three-point bending tests, indicating that CFRP specimens have better mechanical properties. Full article

This study investigates the quasi-static and viscoelastic properties of additively manufactured (AM) PETG reinforced with short carbon fibres. Samples were manufactured using different parameters in terms of the infill pattern, porosity, and annealing condition. Tensile and compressive tests were conducted to determine quasi-static properties such as Young’s modulus and toughness, and dynamic mechanical analysis was used under a frequency sweep of 1–100 Hz to describe the viscoelastic behaviour of the composites. The major impacts and responses between the print parameters were quantified using Analyses of Variance (ANOVAs), which revealed the major contributor to each mechanical property. Fractography on the tensile samples using scanning electron microscopy demonstrated fibre pull-out, indicating poor fibre–matrix bonding, but also revealed interfacial bonding between raster lines in the annealed samples. This had a prominent effect on the properties of latitudinal samples where the force applied was perpendicular to the raster lines. Generally, porosity appeared to have the greatest contribution to the variance in the mechanical properties, with the exception of the tensile modulus, where the infill pattern had a more substantial effect. Annealing caused a consistent increase in the tensile modulus of the tested samples, which can be used to support the design and optimisation of AM parts when they are used under specific loading conditions. Full article

In recent times, the value of data has grown. This tendency is also observeable in the construction industry, where research and digitalisation are increasingly oriented towards the collection, processing and analysis of different types of data. In addition to planning data, measurement data is a main focus. fibre optic measurements offer a highly precise and comprehensive approach to data collection. It is, however, important to note that this technology is still in research regarding concrete structures. This paper presents two methods of integrating filigree sensors into concrete structures. The first approach entails wrapping a fibre around a tendon duct and analysing the installation and associated measurements. The second method involves bonding polyimide and acrylate-coated fibres with 2K epoxy and cyanoacrylate in the grooves of rebars, exposing them to chemical environments. The resulting measurement data is evaluated qualitatively and quantitatively to ascertain its resilience to environmental factors. These developed criteria are consolidated in a decision matrix. Fibre-adhesive combinations necessitate protection from chemical and mechanical influences. The limitations of the solutions are pointed out, and alternative options are proposed. Full article

This study addresses the structure–property relationship within the green concept of wood fibres with cellulose nanofibre functionalised composites (nW-PPr) containing recycled plastic polyolefins, in particular, polypropylene (PP-r). It focuses especially on the challenges posed by nanoscience in relation to wood fibres (WF) and explores possible changes in the thermal properties, crystallinity, morphology, and mechanical properties. In a two-step methodology, wood fibres (50% wt%) were first functionalised with nanocellulose (nC; 1–9 wt%) and then, secondly, processed into composites using an extrusion process. The surface modification of nC improves its compatibility with the polymer matrix, resulting in improved adhesion, mechanical properties, and inherent biodegradability. The effects of the functionalised WF on the recycled polymer composites were investigated systematically and included analyses of the structure, crystallisation, morphology, and surface properties, as well as thermal and mechanical properties. Using a comprehensive range of techniques, including X-ray diffraction (XRD), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), zeta potential measurements, and dynamic mechanical analysis (DMA), this study aims to unravel the intricate interplay of factors affecting the performance and properties of the developed nanocellulose-functionalised wood fibre–polymer composites. The interfacial adhesion of the nW-PPr polymer composites, crystallisation process, and surface properties was improved due to the formation of an H-bond between the nW coupling agent and neat PP-r. In addition, the role of nW (1.0 wt%) as a nucleating agent resulted in increased crystallinity, or, on the other hand, promoted the interfacial interaction with the highest amount (3.0% wt%, 9.0% wt%) of nW in the PP-r preferentially between the nW and neat PP-r, and also postponed the crystallisation temperature. The changes in the isoelectric point of the nW-PPr polymer composites compared to the neat PP-r polymer indicate the acid content of the polymer composite and, consequently, the final surface morphology. Finally, the higher storage modulus of the composites compared to neat r-PP shows a dependence on improved crystallinity, morphology, and adhesion. It was clear that the results of this study contribute to a better understanding of sustainable materials and can drive the development of environmentally friendly composites applied in packaging. Full article

Additively manufactured fibre-reinforced polymers are gaining traction. After the development and optimisation of a novel fibre-deposition system in a laser sintering (LS) setup, polyamide 12 specimens were produced with and without glass fibres. In this study, the relation between the crystallinity, porosity, and mechanical properties of LS specimens with and without fibres is investigated. After testing as-built LS specimens, a detrimental effect of the fibres on the specimens’ performance was observed with a decrease in UTS of 6%. The degree of crystallinity remained the same; however, a porosity content of 2.6% was observed in specimens with fibres. These pores can have a negative influence on the bonding between the fibres and the matrix. To investigate the influence of the pores, warm isostatic pressing (WIP) was performed on LS specimens with and without fibres. The WIP process shows a positive influence on the specimens without fibres, resulting in an increase in UTS of 8.5%. The influence of the WIP process on specimens with fibres, however, is much less pronounced, with an increase in UTS of only 2%. Neither the crystallinity nor the porosity are the cause of the less-than-expected increase in UTS in LS specimens with fibres. A number of hypotheses and mitigation strategies are provided. Full article

This paper investigates making an injection mouldable conductive plastic formulation that aims for conductivity into the electromagnetic interference (EMI) shielding range, with good mechanical properties (i.e., stiffness, strength, and impact resistance). While conductivity in the range (electrostatic charge dissipation) and EMI shielding have been attained by incorporating conductive fillers such as carbon black, metals powders, and new materials, such as carbon nanotubes (CNTs), this often occurs with a drop in tensile strength, elongation-to-break resistance, and impact resistance. It is most often the case that the incorporation of high modulus fillers leads to an increase in modulus but a drop in strength and impact resistance. In this work, we have used short carbon fibres as the conductive filler and selected a 50/50 PBT/rPET (recycled PET) for the plastic matrix. Carbon fibres are cheaper than CNTs and graphenes. The PBT/rPET has low melt viscosity and crystallises sufficiently fast during injection moulding. To improve impact resistance, a styrene-ethylene-butadiene-styrene (SEBS) rubber toughening agent was added to the plastic. The PBT/rPET had very low-impact resistance and the SEBS provided rubber toughening to it; however, the rubber caused a drop in the tensile modulus and strength. The short carbon fibre restored the modulus and strength, which reached higher value than the PBT/rPET while providing the conductivity. Scanning electron microscope pictures showed quite good bonding of the current filler (CF) to the PBT/rPET. An injection mouldable conductive plastic with high conductivity and raised modulus, strength, and impact resistance could be made. Full article

Incomplete data indicate that coal gangue is accumulated in China, with over 2000 gangue hills covering an area exceeding 200,000 mu and an annual growth rate surpassing 800 million tons. This accumulation not only signifies a substantial waste of resources but also poses a significant danger to the environment. Utilizing coal gangue as an aggregate in the production of coal-gangue concrete offers an effective avenue for coal-gangue recycling. However, compared with ordinary concrete, the strength and ductility of coal-gangue concrete require enhancement. Due to coal-gangue concrete having higher brittleness and lower deformation resistance than ordinary concrete, basalt fibre (BF) is a green, high-performance fibre that exhibits excellent bonding properties with cement-based materials, and polypropylene fibre (PF) is a flexible fibre with high deformability; thus, we determine if adding BF and PF to coal-gangue concrete can enhance its ductility and strength. In this paper, the stress–strain curve trends of different hybrid basalt–polypropylene fibre-reinforced coal-gangue concrete (HBPRGC) specimens under uniaxial compression are studied when the matrix strengths are C20 and C30. The effects of BF and PF on the mechanical and energy conversion behaviours of coal-gangue concrete are analysed. The results show that the ductile deformation of coal-gangue concrete can be markedly enhanced at a 0.1% hybrid-fibre volume content; HBPRGC-20-0.1 and HBPRGC-30-0.1 have elevations of 53.66% and 51.45% in total strain energy and 54.11% and 50% in dissipative energy, respectively. And HBPRGC-20-0.2 and HBPRGC-30-0.2 have elevations of 31.95% and 30.32% in total strain energy and −3.46% and 28.71% in dissipative energy, respectively. With hybrid-fibre volume content increased, the elastic modulus, the total strain energy, and the dissipative energy all show a downward trend. Therefore, 0.1% seems to be the optimum hybrid-fibre volume content for well-enhancing the ductility and strength of coal-gangue concrete. Finally, the damage evolution and deformation trends of coal-gangue concrete doped with fibre under uniaxial action are studied theoretically, and the constitutive model and damage evolution equation of HBPRGC are established based on Weibull theory The model and the equation are in good agreement with the experimental results. Full article

Abaca fibres that have excellent mechanical properties are widely applied in the production and preparation of eco-friendly polymer composites as reinforcement materials. However, the weak interfacial bonding property of the abaca fibre and composite matrix limits the further extended application of abaca fibre-reinforced polymer composites. In this research, the findings demonstrate that, compared to raw abaca fibres, the interfacial shear strength (IFSS) value between the treated fibre and matrix is improved by 32% to 86%. Moreover, chemically treated abaca fibres could not only improve the wear resistance of the polymer composites, but also could promote the formation of primary and secondary plateaus. The best wear resistance behaviour was demonstrated by the sample with abaca fibres treated with 3% NaOH and 5% silane solutions, which had a maximum reduction in the sum wear rate of 28.44%. This research will provide detail on theoretical guidance and technical support for the development of eco-friendly natural fibre-reinforced polymer composites. Full article

Laminated metal-composite structures, also known as fibre metal laminates (FMLs), have emerged as prominent engineering materials in various industries, particularly in the domains of aircraft and automobile manufacturing. These materials are sought after due to their enhanced impact and fatigue resistance capabilities. The machining of FMLs plays a crucial role in achieving near-net shapes for the purpose of joining and assembling components. Delamination is a prevalent issue encountered during the process of conventional machining, thus rendering FMLs are challenging materials to machine. This study aims to investigate the cutting process of novel fibre intermetallic laminates (FILs) using the abrasive water jet (AWJ) cutting technique. The FILs consists of carbon and aramid fibers that are adhesively bonded with a resin matrix filled with reduced graphene oxide (r-GO) nano fillers. Moreover, these laminates contain embedded Nitinol shape memory alloy sheets as the skin materials. Specifically, the study aims to investigate the impact of different factors, such as the addition of reduced graphene oxide (r-GO) in the laminates (ranging from 0 to 2 wt%), traverse speed (ranging from 400 to 600 mm/min), waterjet pressure (ranging from 200 to 300 MPa), and nozzle height (ranging from 2 to 4 mm), on the material removal rate (MRR), delamination factor (FD), and kerf deviation (KD). ANOVA was used in the statistical analysis to determine the most influential parameters and their effects on the selected responses. The optimal AWJC parameters are determined using a metaheuristic-based moth–flame optimization (MFO) algorithm in order to enhance cut quality. The efficacy of MFO is subsequently compared with similar well-established metaheuristics such as the genetic algorithm, particle swarm algorithm, dragonfly algorithm, and grey-wolf algorithm. MFO was found to outperform in terms of several performance indices, including rapid divergence, diversity, spacing, and hypervolume values, among the algorithms compared. Full article

Plant fibres are promising candidates to replace synthetic fibres in polymer matrix composites. However, there is still an important issue to overcome: the poor quality of adhesion at the fibre/matrix interface. Many surface treatments of plant fibres have been developed, most of them based on non-environmentally friendly processes. In this paper, a 100% natural treatment is proposed. Hemp yarns are immersed in tap water until the natural growth of limestone beads attached to their surface occurs. The morphology analysis reveals that these calcium carbonate crystals have a nanoneedle architecture, with hemp fibres acting as nucleators for these highly ordered coral-like structures. Tensile tests on ±45° woven hemp/epoxy composites show that the presence of CaCO₃ beads improves the adhesion quality of the fibre/matrix interface and, therefore, increases Young’s modulus value. Full article