Search Results (223)

In the medical industry, strong disinfectants are used to limit bacterial proliferation on the surface of polymer-based materials; however, they may leave hazardous residues. To prevent potential harm to human health, safer disinfection substitutes are continuously searched. This study evaluates the effect of a natural biocidal modifier, geraniol (GR), on the properties of flax-reinforced biocomposites. Biocomposites containing 80 wt% polylactide (PLA) and 20 wt% flax fibres were prepared, and fibres were modified with 1%, 5%, 10%, or 20% GR. The materials were examined using tensile tests, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), thermogravimetry (TG), contact angle measurements, scanning electron microscopy (SEM), and antibacterial activity tests. The incorporation of flax fibres increased the storage modulus from 2730 MPa (PLA) to 3447 MPa, while GR-modified fibres further enhanced stiffness up to 3769 MPa for the 20% GR sample. Strong antibacterial activity against Escherichia coli and Staphylococcus aureus was achieved in biocomposites containing ≥10% GR, with R = 5 and R ≥ 6, respectively. Surface hydrophobicity also improved progressively, and a water contact angle of 92° was obtained at 20% GR. These results demonstrate that geraniol-modified flax fibres effectively impart antibacterial activity and hydrophobicity to PLA biocomposites, indicating their potential for use in sustainable packaging applications and materials for the medical sector. Full article

The evolution of tennis equipment is fundamentally linked to advances in materials science and engineering, which have enabled enhanced player performance through optimised racquet and string designs. This review comprehensively examines the critical role of modern composite materials, manufacturing methods, and string technologies in tennis equipment, focusing on how these elements influence mechanical performance and player experience. It first explores the contributions of matrix and reinforcing materials, particularly carbon fibre and aramid composites, to racquet stiffness, strength, and vibration damping. Next, it details advanced manufacturing techniques such as prepreg layup, autoclave curing, and hollow moulding, which enable precise control over mechanical properties and quality assurance. This paper further evaluates various string materials including natural gut, Kevlar, polyester, nylon, and emerging hybrid setups, analysing their mechanical characteristics, tension maintenance, and impact on ball response and player comfort. Special attention is given to the interaction between design choices and playing conditions, such as court surfaces and player sensitivity, underscoring the complex interplay between equipment mechanics and gameplay dynamics. Through an interdisciplinary lens, this paper synthesises current scientific knowledge and experimental findings, providing a critical foundation for optimising tennis equipment design. By integrating materials science with practical application, this paper provides a comprehensive understanding of tennis equipment design, identifying gaps in current research and offering insights to guide future innovation for manufacturers, coaches, and players. Full article

Lupin (Lupinus spp.), a legume known for its high protein content, holds great promise as a sustainable protein source to meet future global demands. Despite its nutritional benefits, including substantial dietary fibre and bioactive compounds, lupin remains underutilised in human diets due to several techno-functional and sensory limitations. This review delves into the techno-functional limitations of lupin, which include poor foaming capacity, low water and oil absorption, inadequate emulsification properties, and poor solubility. Lupin’s techno-functional limits are tied to the compact, heat-stable nature of its conglutin storage proteins and high insoluble fibre content. While research has been conducted on fermenting other legumes such as soybeans, chickpeas, peas, and lentils with Exopolysaccharide (EPS) producing bacteria, its application to lupin remains largely unexplored. Crucially, this work is one of the first reviews to exclusively link lupin’s unique protein and fibre structure with the specific polymer chemistry of bacterial EPS as a targeted modification strategy. Current research findings suggest that EPS-producing Lactic Acid Bacteria (LAB) fermentation can significantly improve the techno-functional properties of legumes, indicating strong potential for similar benefits with lupin. The analysis highlights various studies demonstrating the ability of EPS-producing LAB to improve water retention, emulsification, and overall palatability of legume-based products. Furthermore, it emphasises the need for continued research in the realm of fermentation with EPS-producing bacteria to enhance the utilisation of lupin in food applications. By addressing these challenges, fermented lupin could become a more appealing and nutritious option, contributing significantly to global food security and nutrition. Full article

This study developed a natural rubber (NR) composite reinforced with surface-modified pineapple leaf fibres (PALFs) and hemp fibres (HFs) using a layer-by-layer (sandwich-like) fabrication method. The objectives were to increase the utilisation of the natural fibres as reinforcing agents and to investigate the impact of silane fibre surface modification on the properties of the sandwich composites. Fibre surface characterisation was performed using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) to confirm the presence of functional groups from silane and cellulose. The wettability and adhesion properties of the modified fibres were also evaluated. The mechanical properties were investigated via single-fibre tensile tests. Composites with 50 phr silane-treated PALF showed the best compromise in terms of interface adhesion (48.3 mJ/m²) and tensile strength (6 MPa). This result was also supported by scanning electron microscopy (SEM), which revealed the absence of voids between the fibres and the NR matrix. Furthermore, dynamic mechanical analysis showed that the PALF composite treated with silane at 50 phr exhibited the best viscoelastic behaviour. NR composites with 50 phr silane-treated PALF have mechanical properties suitable for potential applications in engineering products. Full article

Biocomposites based on natural fibres represent a promising solution for the circular economy. The aim of this study was to develop and characterise a biodegradable composite based on sheep wool from herds raised in the Kyrgyz Republic and polylactide (PLA 4032D). Composite samples with a wool–PLA ratio of 50:50 were fabricated by thermoforming at a temperature of 168 °C for 30 s (n = 10). Mechanical properties tests were performed (PN-EN ISO 604—compression tests), for impact resistance (Charpy method), differential scanning calorimetry (DSC), and measurements of density and thermal conductivity. Biodegradation samples were subjected to enriched soil conditions for 6 weeks in two variants (with and without irrigation). The results showed that the addition of sheep wool to the PLA matrix significantly increased compressive strength (23.56 ± 5.23 MPa) and impact energy absorption (226.2 ± 23.8 kJ/m²) compared to neat PLA. After biodegradation, a 59% reduction in compressive strength was observed while maintaining an increase in fracture energy, suggesting a change in the failure mechanism. The density (0.27 ± 0.02 g/cm³) and the thermal conductivity (0.127 W/m·K) comparable to polymer foams indicate potential for thermal insulation applications. Microscopy and DSC analysis confirmed complete biodegradation under soil conditions. The developed biocomposite from Kyrgyz sheep wool demonstrates the potential for valorisation of local fibrous waste for biodegradable materials with functional insulation properties. Full article

The growing demand for sustainable materials in construction and sanitation has increased interest in natural fibre-reinforced polymer composites. Rice husk, an abundant agricultural by-product, offers a promising alternative as a reinforcing filler in polypropylene (PP) composites. This study aims to assess the suitability of PP composites reinforced with micronised rice husk particles for application in sanitary components. Two formulations containing 20% and 30% rice husk were developed and characterised. Comprehensive analysis included morphological, thermal, rheological, mechanical, hygroscopic, and tribological testing. Results showed that particles incorporation enhanced thermal stability and crystallinity due to a nucleating effect, with the 30% composite showing higher crystallinity. Thermogravimetric analysis showed that although the T₅% decreased from 374.1 °C for neat PP to 309.2 °C and 296.2 °C for the 20% and 30% composites, respectively, the DTG peak temperatures increased by 15.9 °C and 17.6 °C, indicating a delayed main decomposition stage of PP matrix and enhanced overall thermal stability. Rheological behaviour revealed increased viscosity and pseudoplasticity at higher particle content Mechanical characterisation showed an increase in Young’s modulus from 1021 MPa for neat PP to 1065 MPa (+4%) and 1125 MPa (+10%) for PP_Rice_20% and PP_Rice_30%, respectively. In contrast, the nominal strain at break dropped sharply from 238% (PP) to 30% (PP_Rice_20%) and 16% (PP_Rice_30%). Shrinkage decreased from 1.31% (PP) to approximately 1.05% in both composites, indicating improved dimensional stability. However, water absorption rose from 0.015% (PP) to 0.111% (PP_Rice_20%) and 0.144% (PP_Rice_30%), accompanied by an increase in surface roughness (Sa from 0.34 µm to 0.78 µm and 1.06 µm, respectively). The composite with 20% rice husk demonstrated better filler dispersion, reduced water uptake, and smoother surfaces, making it more suitable for injection-moulded components intended for use in humid environments. Overall, the study supports the use of agricultural residues in high-performance biocomposites, contributing to circular economy strategies and the development of more sustainable polymer-based materials for technical applications. Full article

This study evaluates the effect of chemical treatments on the short-beam shear strength, vibrational, and acoustic performance of banana-fibre-reinforced carbon–Kevlar hybrid composites. Banana fibres were treated with 5% NaOH and 0.5% KMnO₄ to improve fibre surface characteristics and interfacial bonding within a sandwich laminate of carbon–Kevlar intraply skins and banana fibre core fabricated by hand lay-up and compression moulding. Short-beam shear strength (SBSS) increased from 14.27 MPa in untreated composites to 17.65 MPa and 19.52 MPa with KMnO₄ and NaOH treatments, respectively, due to enhanced fibrematrix adhesion and removal of surface impurities. Vibrational analysis showed untreated composites had low stiffness (7780.23 N/m) and damping ratio (0.00716), whereas NaOH treatment increased stiffness (9480.51 N/m) and natural frequency (28.68 Hz), improving rigidity and moderate damping. KMnO₄ treatment yielded the highest damping ratio (0.0557) with reduced stiffness, favouring vibration energy dissipation. Acoustic tests revealed KMnO₄-treated composites have superior sound transmission loss across low to middle frequencies, peaking at 15.6 dB at 63 Hz, indicating effective acoustic insulation linked to better mechanical damping. Scanning electron microscopy confirmed enhanced fibre impregnation and fewer defects after treatments. These findings highlight the significant role of chemical surface modification in optimising structural integrity, vibration control, and acoustic insulation in sustainable banana fibre/carbon–Kevlar hybrids. The improved multifunctional properties suggest promising applications in aerospace, automotive, and structural fields requiring lightweight, durable, and sound-mitigating materials. Full article

This Special Issue presents recent advances in the production, modelling, processing, and characterization of advanced industrial materials, highlighting the diversity and sophistication of contemporary research discussing metallic, polymeric, composite, and nano-structured systems. The collected contributions address key challenges in materials science, ranging from surface quality control, the development of novel machining and fabrication tools, and optimization of thermoplastic composite consolidation, to provide fundamental insights into additive manufacturing, rheology, and constitutive modelling. The showcased studies introduce innovative approaches to metrology, including advanced optical, fluorescence, and X-ray scattering techniques for characterizing nano-particles, microstructures, and thermal properties. The presented research also features investigations into the welding of dissimilar steels, binder jetting of stainless steel, and the influence of heat treatment on functional steel performance, alongside environmentally oriented research on natural-fibre energy devices and bio-based polymer composites. Further research topics include defect structures in doped crystals, low-temperature synthesis of oxide films, and mechanical behaviour of steels under extreme conditions. Collectively, these articles demonstrate the strong synergy between experimental methods, computational modelling, and industrial applications, underscoring the continued progress in materials reliability, surface engineering, and advanced manufacturing technologies. This Special Issue therefore provides a comprehensive overview of current trends and emerging directions, offering valuable methodological and conceptual insights in the field. Full article

Cement composites are non-flammable, and their resistance to high temperatures is only apparent. This article presents extensive research on the strength parameters of building mortars exposed to fire-simulating conditions. The analyses included assessment of the mortars’ tensile, compressive and flexural strength, as well as their flexural modulus of elasticity. Microscopic analysis of the samples was performed using a scanning electron microscope (SEM). The results of optimisation studies, particularly tensile strength tests conducted for various types of additives (fibres), showed that the addition of polypropylene fibres had a beneficial effect across the entire temperature range. Based on the research, relationships between temperature and the tested parameters were developed. Polynomial models were applied for their approximation, with the selection justified both by the high consistency with the experimental results and by the nature of the physical changes occurring in the cement mortar during subsequent stages of heating. These models allow an approximate assessment of the condition of mortar after a fire. Based on the conducted microstructural analyses of mortars and their correlation with the strength test results, graphical models were presented to illustrate the phenomena governing the changes in the examined parameters at various fire temperatures. On the basis of conclusions drawn from the analyses, recommendations were formulated regarding the use of polypropylene fibres in selected structural elements that may be exposed to fire, and the limitations of their applicability were indicated. Full article

The growing demand for sustainable, high-performance, and structurally reliable construction materials has intensified research on natural fibre-reinforced composites (NFCs). Among these, hemp stands out due to its high cellulose content, low density, excellent tensile strength, and renewability, making it a promising reinforcement for cementitious and other inorganic matrices, including lime- and geopolymer-based systems. This review focuses exclusively on structural and civil engineering applications, while polymer-based composites are mentioned only for comparative context regarding adhesion and durability. A comprehensive bibliometric and technical analysis was conducted to evaluate the effectiveness of hemp fibre treatment methods in improving fibre–matrix adhesion, mechanical performance, and long-term durability. A systematic search covering major scientific databases from 2014 to 2024 identified global research trends, key treatment techniques, and their performance outcomes. Both chemical (alkaline, silane, acetylation, alkyl ketene dimer—AKD) and physical (plasma, ozone) modification strategies were critically assessed for adhesion, mechanical strength, hydrophobicity, and resistance to environmental cycling. Quantitative results indicate that combined alkaline–AKD treatments produce the most consistent improvement, increasing compressive strength by approximately 30% and flexural strength by up to 25% compared with untreated composites. Physical surface treatments were also found to enhance roughness and interfacial bonding without degrading fibre integrity. Unlike previous reviews that address natural fibres in general, this article specifically targets hemp fibre treatments for inorganic matrices, correlating modification mechanisms with the structural performance indicators relevant to civil engineering. By integrating bibliometric mapping of research evolution, keyword networks, and technological gaps, this review provides a quantitative and engineering-oriented synthesis that highlights its original contribution to sustainable and resilient construction materials. The findings emphasise the need for standardised testing protocols and performance-based evaluations to enable the broader structural application of hemp-based composites in modern construction. Full article

This study investigates the elastic properties of bio-epoxy composites reinforced with natural fibres (flax, hemp) and synthetic fibres (S-glass), with particular focus on the effect of the fibre volume fraction (VF) ranging from 10% to 70%. Three-dimensional representative volume element (RVE) models were developed for single-fibre, hybrid, and multi-fibre systems. The mean-field homogenisation (MF) approach, based on the Mori–Tanaka scheme, and finite element analysis (FEA) with periodic boundary conditions were employed to predict the effective elastic properties, including longitudinal, transverse, and shear moduli, as well as Poisson’s ratio. These numerical predictions were validated against analytical models, including the rule of mixtures, Chamis, and composite cylinder assemblage (CCA) methods. The results demonstrate that increasing the VF enhances longitudinal, transverse, and shear moduli while reducing Poisson’s ratio in natural fibre composites. The good agreement between numerical, semi-analytical, and analytical methods validates the 3D RVE models as useful tools for predicting the properties of multi-hybrid natural fibre composites, supporting their design for lightweight structural applications. Full article

The natural frequencies and damping characterisation of a new aerospace grade composite material were investigated using a modified impulse method combined with the half power bandwidth method, which is applicable to the structures with a low damping. The composite material of interest was unidirectional carbon fibre reinforced plastic. The tests were carried out with three identical square 4.6 mm thick plates consisting of 24 plies. The composite plates were clamped along one edge in a SignalForce shaker, which applied a sinusoidal signal generated by the signal conditioner exiting the bending modes of the plates. Laser vibrometer measurements were taken at three points on the free end so that different vibrational modes could be obtained: one measurement was taken on the longitudinal symmetry plane with the other two 35 mm on either side of the symmetry plane. The acceleration of the clamp was also recorded and integrated twice to calculate its displacement, which was then subtracted from the free end displacement. Two material orientations were tested, and the first four natural frequencies were obtained in the test. Damping was determined by the half-power bandwidth method. A linear relationship between the loss factors and frequency was observed for the first two modes but not for the other two modes, which may be related to the coupling of the modes of the plate and the shaker. The experiment was also modelled by using the Finite Element Method (FEM) and implicit solver of LS Dyna, where the simulation results for the first two modes were within 15% of the experimental results. The novelty of this paper lies in the presentation of new experimental data for the natural frequencies and damping coefficients of a newly developed composite material intended for the vibration analysis of rotating components. Full article

The increasing demand for sustainable engineering solutions has driven extensive research into natural fibre-reinforced composites (NFCs), notably flax fibre-reinforced polymers (FFRPs), which offer promising eco-friendly alternatives to synthetic composites. This study presents a comprehensive application of continuum damage mechanics (CDM) methodology to unidirectional (UD) FFRPs, addressing critical gaps in predictive modelling of progressive intralaminar damage for sustainable structural applications. A systematic experimental characterisation protocol was developed to identify material parameters that account for the inherent variability and complex nonlinear behaviour of natural fibres. The CDM model was calibrated using comprehensive quasi-static testing on multiple laminate configurations and validated through finite element analysis (FEA) in Siemens Simcenter Samcef. The model accurately captures the nonlinear behaviour and damage mechanisms of notched flax–epoxy laminates, achieving prediction accuracies of 97.61% and 88.98% for the force-displacement response in open-hole tensile (OHT) validation tests. Integrating experimental characterisation with FEA enables robust virtual prototyping of sustainable composite structures, supporting design optimisation and lifecycle assessment. This research establishes validated damage modelling methodologies for eco-friendly NFC, facilitating accelerated adoption in automotive, marine, and construction sectors. Full article

Fibres play a crucial role in diverse biomedical applications, ranging from tissue engineering to drug delivery. Electrospinning has emerged as a simple and versatile technique for producing ultrafine fibres at micro- to nanoscale dimensions. Synthetic biopolymers are effective cues to replace damaged tissue in the biomedical field, both in vitro and in vivo applications. Among them, poly (L-lactic acid) (PLLA) is a renewable, environmentally friendly biopolymer material. Polycaprolactone (PCL) is a synthetic polymer with good biocompatibility and biodegradation characteristics. However, both electrospun PLLA and PCL fibres have their limitations. To overcome these shortcomings, electrospinning PLLA/PCL blend fibres has been the subject of many studies. This review discusses the different parameters for the electrospinning of PLLA/PCL-based fibres for biomedical applications. Furthermore, we also discuss how electrospun PLLA/PCL-based scaffolds can be modified or combined with other biomaterials, such as natural polymers and bioceramics, and examine their in vitro and in vivo applications in various tissue repair strategies. Full article

A biomimetic adaptive façade applies natural principles to building design using shading devices that dynamically respond to environmental changes, enhancing daylight, thermal comfort, and energy efficiency. While motorised systems offer precision through sensors and mechanical actuation, they consume energy and are complex. In contrast, passively actuated systems use smart materials that respond to environmental stimuli, offering simpler and more sustainable operation, but often lack responsiveness to dynamic conditions. This study explores a sequential approach by initially developing motorised shading concepts before transitioning to a passive actuation strategy. In the first phase, nine mechanically actuated shading device concepts were designed, inspired by the opening and closing behaviour of plant stomata, and evaluated on structural robustness, actuation efficiency, ease of installation, and visual integration. One concept was selected for further development. In the second phase, a biocomposite made of polylactic acid (PLA) and regenerated cellulose fibres was used for Fused Deposition Modelling (FDM) to fabricate 3D-printed modules with passive, moisture-responsive actuation. The modules underwent environmental testing, demonstrating repeatable shape changes in response to heat and moisture. Moisture application increased the range of motion, and heating led to flap closure as water evaporated. Reinforcement and layering strategies were also explored to optimise movement and minimise unwanted deformation, highlighting the material’s potential for sustainable, responsive façade systems. Full article