Search Results (239)

In this study, an active vibration control (AVC) strategy is effectively used on a system made of a honeycomb polymer–paper core and carbon fiber-reinforced polymer (CFRP) plates. A cost-effective and practical solution based on an AVC system has been developed and tested using a microcontroller unit (MCU) from Texas Instruments. The control system is studied by applying out-of-plane disturbances to the composite panel via an electrodynamic shaker, by exciting the identified mode shapes obtained through experimental modal analysis, i.e., impact tests. The actuator chosen for the AVC system is a Macro Fiber Composite (MFC) patch. Multiple analog signal processing circuits were developed to scale and shift the signal at the input and output of the MCU. The proposed control algorithm is based on a positive position feedback (PPF) technique. Modal analysis was performed to identify the natural frequencies and mode shapes of the structure, which are essential for the design and tuning of the modal-based PPF controller. This analysis also enabled optimal sensor and actuator placement, ensuring effective targeting and control of the dominant vibration modes. Then, a series of tests were performed using pure sine excitations at frequencies of interest, close to the 2nd and 8th mode at 25.13 Hz and 129 Hz, respectively. The results of the experiments revealed a velocity attenuation of 55.8% to 76.9% and a Power Spectral Density (PSD) attenuation of 5.8 dB to 12.8 dB, depending on the mode under study. Owing to the size and mass properties of the Macro Fiber Composite (MFC) patches, the control system is very much suitable for automobile and aerospace applications. Full article

Yucca decipiens is a native species from arid and semi-arid regions with emerging nutritional and biotechnological potential. This study evaluated its proximate composition, elemental profile determined by inductively coupled plasma mass spectrometry (ICP-MS), and growth performance under nursery conditions. Proximate analysis revealed a high dietary fiber content in leaves (58.93%) and higher carbohydrate levels in stems (28.83%). Free amino acid content was significantly higher in stems (2.75 g histidine equivalents kg⁻¹) than in leaves (1.76 g kg⁻¹). Multi-elemental profiling (63 elements) showed organ-specific accumulation patterns, with essential macro- and micronutrients predominantly concentrated in leaves, including potassium (28,334 ppm) and calcium (15,345 ppm), while iron was the most abundant trace element in stems (1253 ppm). Principal component analysis (PCA) revealed clear organ-specific mineral partitioning between leaves and stems, indicating differentiated physiological roles and potential selective biomass utilization. Growth assessment conducted over a two-year period demonstrated steady biomass accumulation and good adaptive performance under nursery conditions. Overall, the results highlight the emerging nutritional and agroindustrial relevance of Yucca decipiens for applications in semi-arid environments. Full article

In aerospace applications, the vibration of aircraft structures results in a reduction in their fatigue life. Vibration-suppression technology utilizing macro fiber composite (MFC) materials constitutes a significant research direction. Aiming at the specific requirements of the MFC actuator operating in the asymmetric high-voltage range of −500 V to 1500 V and the miniaturization of the drive system for aircraft, this study designs a compact self-tuning digital high-voltage controller which adopts a discontinuous conduction mode (DCM) flyback topology as the fundamental model for the switching power supply high-voltage controller, uses the STM32G431 chip as the main controller, and incorporates a Type-II digital compensator designed to enhance the system stability under constant parameters. A Backpropagation (BP) neural network is proposed to enable dynamic adjustment of the digital compensator control parameters, thereby achieving self-tuning, while also supporting program download and real-time data transmission. The high-voltage controller effectively addresses the size and weight constraints in vibration active control systems. Laboratory tests demonstrated its excellent transient response and robust load-driving capability. Vibration-suppression experiments on a high-aspect-ratio UAV wing achieved a 74% vibration attenuation rate, validating the effectiveness of the proposed high-voltage controller. Full article

Carbon fiber-reinforced thermoplastic (CFRTP) composites are now widely used in many fields. Ultrasonic welding (UW) is a key technology for joining these materials. The control mode of UW has a great effect on the quality of the welded joints. However, there is still not enough research comparing the different welding control modes. This paper investigates the effects of the time control, energy control, and displacement control modes on the ultrasonic welding quality of carbon fiber-reinforced polycarbonate (CF/PC). A flat PC film is used as the energy director (ED). The evaluation focuses on the lap-shear strength (LSS), macro- and micro-morphology, fracture surface characteristics and power–displacement curves of the welding process. Furthermore, significant differences are observed in the temperature field evolution and joint failure modes across the different control modes and process parameters. Results indicate that the displacement control mode achieves the highest joint quality and process stability, yielding a maximum LSS of 30.6 MPa. A correlation analysis reveals that the displacement–energy relationship exhibits the strongest coupling, and the Pearson correlation coefficient r is 0.896. Full article

The construction sector faces increasing pressure to reduce the embodied energy of building materials while valorizing industrial waste streams. This study evaluates the direct incorporation of post-industrial textile waste (100% cotton and cotton–polyester blends) in its native form to develop high-performance cementitious ceiling sheets. Composites were fabricated under a controlled hydraulic compaction pressure of 2.0 MPa, optimized to achieve matrix densification while preserving the integrity of the fibrous network. Viscoelastic recovery of the compressed fibers induced a hierarchical double-porosity architecture characterized by macro-voids and hollow fiber lumens. This microstructural evolution reduced thermal conductivity to 0.091 W/m·K, approximately 50% lower than commercial cement–fiber benchmarks—without compromising mechanical compliance. Scanning Electron Microscopy (SEM) revealed a mechanistic decoupling between water absorption and dimensional stability. Although the CP15 formulation (15 wt.% cotton–polyester) exhibited high moisture uptake (~21%), thickness swelling remained limited to 1.35%. This dimensional stability is attributed to the hydrophobic polyester framework, which bridges microcracks and constrains hygroscopic expansion within the cellulosic phase. The optimized CP15 composite achieved a Modulus of Rupture (MOR) of 8.75 MPa, exceeding ISO 8336 Category C, Class 2 requirements. Despite increased thickness, the areal density (10.84 kg/m²) remains compatible with standard gypsum-grade suspension systems, eliminating the need for structural modification. These findings establish a scalable, direct-valorization strategy for circular construction materials delivering enhanced thermal insulation and robust performance under tropical climatic conditions. Full article

Carbon fiber-reinforced thermoplastic composites (CFRTP) are widely used in automotive, aerospace, and other industries due to their lightweight, high specific strength, recyclability, and superior thermal properties. However, their non-homogeneity and anisotropy present challenging machining characteristics, often leading to damage that deteriorates component performance. It is imperative to conduct numerical simulation and experimental studies on CFRTP to systematically analyze the relationship between cutting mechanisms and the surface integrity of CFRTP. This study aimed to establish an innovative three-dimensional micro-scale cutting numerical model that integrates the differentiated constitutive behaviors and damage criteria of carbon fibers, matrices, and fiber–matrix interfaces—enabling precise characterization of micro-scale damage evolution during cutting. By combining simulation with experimental verification, it unveils the material removal mechanisms and processing damage causes of CF/PEEK, and further pioneers the quantification of the gradient correlation between fiber orientations (0°, 45°, 90°, and 135°) and fracture modes, cutting forces, and surface integrity, thereby addressing the gap of micro-mechanism and quantitative analysis in CFRTP machining. The micro-scale damage mechanisms revealed by the model directly reflect the intrinsic response of individual fibers in the tow, and the collective effect of these micro-behaviors determines the macro-scale machining performance observed in the experiments. A right-angle cutting experiment was conducted to validate the accuracy of the micro-scale numerical model. The mechanisms of fiber fracture, damage patterns, and chip morphology were systematically compared. The experimental results demonstrate good agreement with the outcomes of the numerical simulations. This study aims to bridge the gap between theoretical understanding and practical application of the cutting mechanisms in CFRTP, providing valuable insights for advancements in manufacturing processes. Full article

The pursuit of alternatives to nonrenewable materials has stimulated the development of sustainable materials with improved performance, particularly polymer composites reinforced with plant-based fibers. In this study, eucalyptus fibers were thermally treated and evaluated as eco-friendly reinforcements for polyester composites, aiming to enhance their physical and mechanical properties. The fibers were subjected to heat treatments between 140 and 230 °C in a Macro-ATG oven, followed by analyses of anatomical characteristics and chemical composition. Composites containing 25% fiber reinforcement were produced using an orthophthalic unsaturated polyester matrix catalyzed with methyl ethyl ketone peroxide, with untreated fibers used as references. Thermal treatment induced significant modifications in fiber morphology and composition, including increases in cell wall fraction at 170 and 200 °C and higher cellulose contents at 140 and 170 °C. Mechanical performance was assessed through tensile, flexural (modulus of rupture—MOR), modulus of elasticity (E_B), and impact tests. Composites reinforced with heat-treated fibers exhibited lower apparent density and, notably, those treated at 230 °C showed markedly reduced water absorption and enhanced tensile strength compared with the control. Overall, treatment at 230 °C proved most effective, highlighting the potential of thermally modified eucalyptus fibers as viable reinforcements for high-performance, bio-based polymer composites. Full article

Intensive livestock and aquaculture systems require high-quality feeds with the correct nutritional composition. The decrease in wild fish proteins has led to demands within the feed supply chain for new alternatives to fulfil the growing demand for protein. In this context, edible insects like the yellow mealworm (Tenebrio molitor) have the greatest potential to become a valid alternative source of proteins. This study evaluated the growth performance and nutritional profile of yellow mealworm larvae reared under laboratory conditions on eight different agro-industrial by-products: wheat middling, durum wheat bran, rice bran, hemp cake, thistle cake, dried brewer’s spent grains, dried tomato pomace, and dried distilled grape marc. The quantitative and qualitative impacts of rearing substrates on larvae were compared. The results showed that larvae adapt well to different substrates with different nutritional compositions, including the fibrous fraction. However, substrates affect larval growth feed conversion and larval macro composition. Hemp cake stood out for its superior nutritional value, as reflected by its high protein content and moderate NDF (Neutral Detergent Fiber) levels, which determine fast larval growth. On the contrary, imbalanced substrate lipid or carbohydrate content (rice bran), as well as the presence of potential antinutritional compounds (thistle cake), appeared to negatively affect growth performances. Full article

Prunus spinosa L. is a shrub with nutritional potential, yet limited information is available on the composition of its stone fruit and leaves. This study aimed to investigate and compare the macro and micronutrients, fatty acid profile, and lipophilic and hydrophilic antioxidant compounds in fruits and leaves, as well as their potential functional properties. The results revealed that leaves contain higher crude protein (10.94%) than fruits (6.46%) but lower crude fiber (13.86% compared to 22.16%). The iron (370.37 mg/kg) and manganese (43.57 mg/kg) were significantly higher (p < 0.05) in leaves than in fruits (44.87 versus 7.02 mg/kg). The fruits’ lipid profile was rich in monounsaturated fatty acids (56.8%), whereas the leaves showed higher saturated fatty acids (38.3%) and polyunsaturated fatty acids (43.7%). The leaves also presented significantly higher n-3 content (25.2%) compared with fruits (1.80%). The antioxidant compounds were higher in the leaves, with total vitamin E exceeding 1268 mg/kg, primarily α-tocopherol (1214.98 mg/kg) isoform, lutein (409.38 mg/kg), and astaxanthin (3.74 mg/kg), compared with only 74.75 mg/kg total vitamin E in the fruits. The total hydroxycinnamic polyphenols in leaves were 92.63% higher in leaves than in fruits, with anthocyanins at 63.23% and flavonols at 95.82%. Although the leaves demonstrated superior antioxidant potential and mineral content compared to the fruits, making it a promising candidate for nutraceutical and functional food applications, the fruits maintained a healthier lipid profile suitable for dietary fat intake. This comparative analysis highlights the distinct nutritional and bioactive composition of Prunus spinosa co-products. Full article

Background: In pediatric celiac disease (CD), intestinal malabsorption and the restrictive nature of a gluten-free diet (GFD) frequently result in persistent macro- and micronutrient imbalances, despite histological remission. The present review evaluates the evidence on nutritional adequacy of the GFD, identifies common deficiencies, and considers biomarker strategies and dietary recommendations to optimize growth and metabolic health. Methods: A narrative review of the literature was conducted, focusing on studies of nutrient intake, product composition of gluten-free foods, biomarker assessment, and clinical outcomes in children with CD. Both macronutrient (protein, fat, carbohydrate, fiber) and micronutrient (iron, vitamin D, calcium, B-vitamins, zinc, magnesium) domains were included. Results: Children with CD on long-term GFD demonstrate higher intake of lipids (especially saturated fat) and simple carbohydrates, alongside consistently low intake of dietary fiber and key micronutrients. Gluten-free products often exhibit lower protein content, higher glycemic index, and reduced fortification compared to gluten-containing equivalents. Nutritional deficits contribute to impaired linear growth, delayed puberty and increased metabolic risk. Conclusions: Nutritional adequacy of the GFD cannot be assumed in children with CD. Routine monitoring using standardized biomarker panels, combined with personalized dietary counseling and improved formulation and fortification of gluten-free products, is essential to mitigate long-term adverse outcomes. Future work should advance precision nutrition approaches and public-health initiatives to optimize dietary quality in this vulnerable population. Full article

In response to the increasing consumer demand for healthier diets and the needs of individuals with gluten intolerance, chestnut flour (CF) emerges as a valuable unconventional ingredient for sustainable and functional nutrition. This study evaluated the nutritional, phytochemical, and functional properties of gluten-free biscuits formulated with whole rice flour (RF), CF, and their mixtures, where RF was replaced by CF at 0% (control), 10%, 30%, 70%, 90%, and 100% (w/w). In addition, in the 50% CF formulation, 5% of RF was substituted with fruit powders rich in phenolic compounds and recognized as fortifying agents, such as chokeberry (CP), açaí (AP), and blueberry (BP). Proximate composition, macro- and microelement content, total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity (DPPH and FRAP assays) were determined for the individual flours, composite flours, fruit powders, and biscuit formulations. Structural characteristics were assessed using Small- and Wide-Angle X-ray Scattering (SAXS/WAXS) analysis and Fourier Transform Infrared Spectroscopy (FTIR). Results showed that CF incorporation enhanced both the nutritional and functional profile of flours and biscuits, increasing protein, fiber, lipid, and mineral contents while reducing carbohydrates, and improving TPC, TFC, DPPH, and FRAP values. Fortification with 5% CP, AP, or BP further boosted the phytochemical content of the biscuits, with the chokeberry-enriched sample exhibiting the highest TPC (348.88 mg GAE/100 g d.s.), TFC (253.82 mg QE/100 g d.s.), DPPH (50.36%), and FRAP (21.07 μM Fe²⁺/g d.s.). The combination of 50% CF and 5% CP provided dual benefits, significant bioactive enrichment alongside the preservation of desirable technological properties. Complementary SAXS/WAXS and FTIR analyses indicated that CF and fruit powders enhanced molecular interactions and matrix cohesion, which may contribute to improved texture and antioxidant potential of the biscuits. Overall, this formulation offers a promising and practical approach to developing functional gluten-free biscuits with enhanced nutritional, phytochemical, functional, and structural characteristics. Full article

The study and preservation of illuminated manuscripts, particularly miniatures on parchment, are crucial for understanding the artistic, cultural, and technological history of the past. This research investigates the materials used in a 16th-century illuminated scroll, analyzing both the miniatures and the written text through non-invasive techniques. A multi-analytical approach was applied, including optical microscopy, Hypercolorimetric Multispectral Imaging (HMI), infrared reflectography in the 950–1700 nm range, Fiber Optics Reflectance Spectroscopy (FORS), macro X-ray fluorescence (MA-XRF) spectroscopy, Raman spectroscopy, and External Reflection Fourier Transform Infrared (ER-FTIR) spectroscopy. These methods provided a comprehensive characterization of the painting materials’ chemical composition and the artistic techniques utilized, revealing new information on Renaissance materials and practices. The detected mineral pigments primarily include smalt, vermilion, lead white, and minium, which are consistent with materials commonly found in illuminated manuscripts. Aluminosilicate and calcite were identified as fillers or substrates utilized for organic dyes, particularly those generating pink hues. An uncommon finding was the green pigment, which was identified as copper hydroxynitrate. Furthermore, gold and silver were extensively employed in the decorative elements, both as metal foils and in shell pigment form. Finally, the capital letters were executed using smalt and vermilion, while the black text ink was characterized as iron gall ink, a composition typically employed on parchment supports. Full article

To enhance the low-frequency vibration suppression capability of cantilever beams, a magnetically tunable piezoelectric cantilever beam structure (MTPCBS) is proposed in this paper. A magnetic spring with negative stiffness (NSMS) is fixed at the free end of a cantilever beam, forming a quasi-zero-stiffness structure. Meanwhile, a macro-fiber composite (MFC) patch is bonded near the root of the beam to implement active skyhook damping control for active vibration control. A theoretical model of the cantilever beam, NSMS, and MFC is established, and the displacement transmissibility of the MTPCBS is derived. The influences of the magnet distance of the NSMS and the control gain of the controller are investigated via simulation. Experimental results indicate that compared to the single beam, the effective vibration isolation frequency of the proposed MTPCBS shifts from 15.3 Hz to 4.6 Hz. When subjected to random vibration excitation ranging from 1 to 80 Hz, the root mean square (RMS) value of vibration decreases from 0.03 g to 1.77 × 10⁻³ g, with the vibration attenuation rate improving from −50% to 91%. The proposed MTPCBS and active–passive vibration control method for cantilever beams significantly enhances low-frequency vibration suppression capabilities, providing a feasible strategy for achieving broadband vibration suppression. Full article

This study explores the synergistic effects of recycled carbon fiber (RCF) and recycled carbon fiber powder (RCFP) on the performance of conductive asphalt mixtures (CAMs). Laboratory tests were conducted to evaluate optimal asphalt content (OAC), electrical and heating behavior, and key pavement properties, including rutting, cracking, and freeze–thaw resistance. Results showed that OAC increased with RCF and RCFP dosage due to their high surface area and strong asphalt absorption. The composite achieved stable conductivity, where RCF formed a macro-scale skeleton and RCFP established a micro-bridging network, reducing resistivity to a minimum of 1.60 Ω·m. This dual conductive mechanism significantly enhanced heating efficiency, with a peak rate of 4.85 °C/min at 0.5% RCF + 3% RCFP. Mechanically, RCF provided three-dimensional reinforcement while RCFP improved cohesion, together enhancing high-temperature and freeze–thaw performance. However, low-temperature cracking resistance exhibited a parabolic trend due to the risk of material agglomeration at excessive dosages. Multi-indicator TOPSIS analysis identified 0.4% RCF + 3% RCFP as the optimal composition. Critically, this optimal mixture is also technically and economically feasible, demonstrating an excellent balance characterized by a low specific energy consumption of 2.38 W·h/°C and a competitive cost (≈CNY 528.4/t). This study provides a sustainable, energy-efficient, and multi-functional solution for pavement heating and de-icing in cold regions. Full article

This study describes the effect of electron radiation on the macro- and micro-mechanical and tribological properties of composite polypropylene filled with 25% glass fiber. Micro-mechanical and tribological properties were investigated both on the sample surface and at various depths below the surface. Polypropylene was irradiated with radiation doses of 15, 33, 45, 66 and 99 kGy. As the results show, electron radiation has an influence on the change in PP’s structure, in which due to the electron radiation, a crosslinked phase and an increase in crystallinity are formed. These changes in morphology are reflected in an enhancement of micro-mechanical and tribological properties both at the surface and in deeper layers below the surface. More crosslinking and recrystallization occur across the sample’s cross-section up to a depth of 2 mm, where greater micro-mechanical and tribological properties are also measured. The difference between the surface and the center of the material can be up to 32%. The optimum radiation dose appears to be 45 kGy, where the maximum crosslinking, highest crystallinity and best micro-mechanical and tribological properties are found. The difference between non-irradiated and irradiated filled PP is 52% in indentation hardness. In terms of macro-mechanical properties, the tensile modulus increased by 44% (45 kGy). This translates into higher surface wear resistance and the overall stiffness of the part. Higher doses of radiation cause the beginning of degradation processes, which are manifested by a decrease in the degree of embedding, crystallinity and thus micro-mechanical and tribological properties. Full article