Search Results (12)

The incorporation of fibers in cement-based materials has gained attention in the construction sector in recent decades, aiming to improve the mechanical performance of composites. This present work evaluates the influence of synthetic and natural fibers as reinforcements in cement mortars, analyzing their effects on both physical and mechanical properties through destructive and non-destructive testing. Polypropylene fibers (PPFs) were considered synthetic reinforcement, whereas alfa fibers (AFs) were selected as a sustainable alternative. Compressive strength, flexural strength and Ultrasonic Pulse Velocity (UPV) were conducted to assess mechanical behavior and material integrity as well as density, water absorption and voids content. Additionally, a statistical approach was performed to compare the properties of both types of fibers and determine their significance in improving mortar properties. The results indicate that both PPFs and AFs significantly improve the flexural strength and promote a ductile failure mode without compromising workability. Moreover, UPV measurements suggest that fiber incorporation does not adversely impair the internal homogeneity of the material. The results obtained confirm the effectiveness of fiber reinforcement, offering valuable insights regarding the potential of AF as a strong candidate for sustainable building purposes and practical applications. Full article

This study investigates the thermal and energy performance of various bio-based materials, including Typha Australis, straw, banana fiber, Alfa fiber, peanut shells, and VSS (a blend of wood pulp, cotton, flax, and hemp), in comparison to conventional concrete. A combined approach integrating numerical simulations and experimental analyses was employed to ensure robust and comprehensive insights. COMSOL Multiphysics was utilized for detailed thermal modeling of wall assemblies, while TRNSYS enabled dynamic simulations to evaluate the impact of these materials on overall cooling energy demand. The results demonstrate that bio-based materials offer significantly improved thermal insulation, reducing air conditioning needs by over 30% relative to concrete, with banana fiber exhibiting the highest performance. This study underscores the need for industrial-scale optimization, supportive regulatory frameworks, and real-world implementation to promote broader adoption. Despite their strong potential, challenges remain, particularly regarding cost-effectiveness, durability, and market penetration. Ultimately, this research advocates for a transition toward more sustainable and environmentally conscious construction practices, aligning with efforts to reduce CO₂ emissions and enhance building energy efficiency. Full article

Composite grids serve as reinforcement in concrete structures, offering alternatives to conventional steel reinforcement. These grids can be fabricated from various materials, including synthetic polymers, metals, and natural fibers. This study explores the use of composite grids as lateral confinement of self-compacting concrete (SCC) cylinders and examines their impact on the failure mode under axial compression. In the experiment, the types of grids and mesh shapes used were plastic grids of diamond mesh (PGD) and regular mesh (PGT), metallic grids of diamond mesh (MGD) and square mesh (MGS), vegetable grids of Alfa fiber mesh, 10 × 10 mm (VGAF-1) and 20 × 20 mm (VGAF-2), and vegetable grids of date palm fibers (VGDF). The binder of SCC mixtures incorporated 10% marble powder as a partial replacement for ordinary Portland cement (OPC). SCC mixtures were tested in the fresh state by measuring the slump flow diameter, V-funnel flow time, L-box blocking ratio, and segregation index. Cylinders with a diameter of 160 mm and a height of 320 mm were made to assess the mechanical properties of hardened SCC mixtures under axial compression. The results indicate that most of the confined cylinders exhibited an increase in ductility compared to unconfined cylinders. Grid types MGD and PGD provided the best performance, with ductility increases of 100.33% and 96.45%, respectively. VGAF-2 cylinders had greater compressive strength than cylinders with other grid types. The findings revealed that the type and mesh shape of the grids affects the failure mode of confined cylinders, but has minimal influence on their modulus of elasticity. This study highlights the potential of lateral grid confinement as a technique for rehabilitating, strengthening, and reinforcing weaker structural concrete elements, thereby improving their mechanical properties and extending the service life of building structures. Full article

The construction industry’s escalating energy demands and greenhouse gas emissions underscore the need for sustainable, high-performance building materials. This study investigates the incorporation of locally sourced alfa fibers (AFs) into plaster-based composites to enhance thermal insulation, reduce environmental impact, and lower production costs. Three distinct AF morphologies—small (<5 mm), medium (10 ± 5 mm), and large (20 ± 5 mm)—were incorporated at fixed mass ratios, and their effects on key material properties were systematically evaluated. The results indicate that integrating AFs into plaster reduces composite density by up to 16.5%, improves thermal characteristics—lowering thermal conductivity and diffusivity by up to 52%—and diminishes both CO₂ emissions and production costs. The addition of fibers also enhances flexural strength (up to 40%) through a fiber bridging mechanism that mitigates crack propagation, although a general decline in compressive strength was observed. Notably, composites containing medium and large fibers achieved significantly lower densities (~1050 kg/m³) and superior thermal insulation (~0.25 W/mK) compared with those with small fibers, with the largest fibers delivering the greatest thermal performance at the expense of compressive strength. Overall, these findings highlight the potential of AF–plaster composites as environmentally responsible, high-performance building materials, while emphasizing the need to carefully balance mechanical trade-offs for structural applications. Full article

The anticoccidial monensin (MON) is a high-concern emerging pollutant. This research focused on six low-cost bio-adsorbents (alfa, cactus, and palm fibers, and acacia, eucalyptus, and zean oak barks), assessing their potential for MON removal. Batch adsorption/desorption tests were carried out, and the results were fitted to the Freundlich, Langmuir, Linear, Sips, and Temkin models. The concentrations adsorbed by the six materials were very similar when low doses of antibiotic were added, while they differed when adding MON concentrations higher than 20 µmol L⁻¹ (adsorption ranging 256.98–1123.98 μmol kg⁻¹). The highest adsorption corresponded to the sorbents with the most acidic pH (<5.5) and the highest organic matter and effective cation exchange capacity values (eucalyptus bark and acacia bark, reaching 92.3% and 87.8%), whereas cactus and palm fibers showed the lowest values (18.3% and 10.17%). MON desorption was below 8.5%, except for cactus and palm fibers. Temkin was the model showing the best adjustment to the experimental data, followed by the Langmuir and the Sips models. The overall results indicate that eucalyptus bark, alfa fiber, and acacia bark are efficient bio-adsorbents with potential for MON removal, retaining it when spread in environmental compartments, reducing related risks for human and environmental health. Full article

Isolation and culturing of cardiac fibroblasts (CF) induces rapid differentiation toward a myofibroblast phenotype, which is partly mediated by the high substrate stiffness of the culture plates. In the present study, a 3D model of Engineered Heart Matrix (EHM) of physiological stiffness (Youngs modulus ~15 kPa) was developed using primary adult rat CF and a natural hydrogel collagen type 1 matrix. CF were equally distributed, viable and quiescent for at least 13 days in EHM and the baseline gene expression of myofibroblast-markers alfa-smooth muscle actin (Acta2), and connective tissue growth factor (Ctgf) was significantly lower, compared to CF cultured in 2D monolayers. CF baseline gene expression of transforming growth factor-beta1 (Tgfβ1) and brain natriuretic peptide (Nppb) was higher in EHM-fibers compared to the monolayers. EHM stimulation by 10% cyclic stretch (1 Hz) increased the gene expression of Nppb (3.0-fold), Ctgf (2.1-fold) and Tgfβ1 (2.3-fold) after 24 h. Stimulation of EHM with TGFβ1 (1 ng/mL, 24 h) induced Tgfβ1 (1.6-fold) and Ctgf (1.6-fold). In conclusion, culturing CF in EHM of physiological stiffness reduced myofibroblast marker gene expression, while the CF response to stretch or TGFβ1 was maintained, indicating that our novel EHM structure provides a good physiological model to study CF function and myofibroblast differentiation. Full article

In recent years, there has been a growing replacement of synthetic fibers by natural ones, particularly by autochthonous materials. In the case of Algeria, the most abundant plant resources are the PALF (Pineapple leaf fiber), the date palm, and the Alfa fibers. In this work, the development and use of analytical and numerical methods are proposed to predict the mechanical properties of layers based on natural fibers that will be applied to manufacture skins of the sandwich cylinder. To achieve these predictions, four analytical models were used, namely the Halpin–Tsai, the Chamis, the Hashin vs. Rosen, and the ROM. The analytical results were compared with the numerical simulations and experimental data. The prediction of the elastic properties of the three fiber-based eco-composites showed an important dispersion in terms of stiffness. Full article

In the present work, we propose to confront two modeling techniques for predicting the macroscopic properties of short alfa fiber-reinforced polypropylene composites. The first modeling was a micromechanical analysis using the Mori-Tanaka, Self-consistent, Diluted, Voigt, Reuss, and Neerfeld-Hill models. The second modeling was digital, using a specific finite element technique called the Projected Fiber (PF) approach. In the framework of this study, both 2D and 3D finite element analyses based on the PF approach were used. First, we proposed an inverse approach using these analytical and finite element models to predict the Young’s modulus of alfa fiber. Then, we compared the obtained results with the experiment values available in the literature. This comparison showed that the micromechanical models underestimated the alfa fiber’s Young’s modulus, while the finite element approach, PF, allowed for good framing of the experimental values. Moreover, we investigated the effect of fiber content on the predicted elastic properties of a polypropylene (PP) matrix reinforced with randomly distributed short alfa fibers. We noticed that the Diluted model was more accurate than the Mori-Tanaka and Self-consistent methods. As for the PF approach, its estimations were close to the experimental values. For example, the Young’s modulus for the PP/alfa with a 30 wt% of fiber content was underestimated with an error of 4.3%. It is shown that the 2D PF approach can provide calculated results with sufficient prediction accuracy. Full article

Purposes: this clinical study evaluated the accuracy and execution time of a digital imaging fiber-optic transillumination (DIFOTI) technique for the detection of approximal caries in posterior teeth compared to intra-oral examination associated with bitewing radiographs. Methods: one hundred patients were selected and submitted to clinical inspection and bitewing radiographs. The outcomes of this process were converted into scores, according to the International Caries Detection and Assessment System (ICDAS): 0—sound tooth; 1, 2, and 3—carious lesion confined within enamel; 4, 5, and 6—dentin carious lesion. Subsequently, an independent investigator acquired digital images of the same teeth using a DIFOTI device (DIAGNOcam, Kavo Dental), which were also converted into ICDAS scores. The time required for executing diagnostic procedures was measured. The clinical sensitivity and specificity of DIFOTI were analyzed by receiver operating characteristic (ROC) curves. The time necessary to perform the diagnostic methods was evaluated by Mann–Whitney U (alfa = 0.05). Results: the overall test accuracy for the DIFOTI-based device ranged from 0.717 to 0.815 (area under the ROC curve) with p < 0.0001 for all ICDAS scores. Bitewing radiographs took almost twice the time required by DIFOTI (p < 0.001). Conclusions: the DIFOTI-based device DIAGNOcam provided accurate detection of approximal caries in posterior teeth, even at early stages. The technique employed for transillumination caries diagnosis by the same device took less time than conventional bitewing radiographs. Clinical Relevance: transillumination devices, such as DIAGNOcam, can be accurately used for caries diagnosis in approximal surfaces of posterior teeth, demanding less clinical time and without radiation-related risks. Full article

Biocomposites based on thermoplastic polymers and natural fibers have recently been used in wind turbine blades, to replace non-biodegradable materials. In addition, carbon nanofillers, including carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs), are being implemented to enhance the mechanical performance of composites. In this work, the Mori–Tanaka approach is used for homogenization of a polymer matrix reinforced by CNT and GNP nanofillers for the first homogenization, and then, for the second homogenization, the effective matrix was used with alfa and E-glass isotropic fibers. The objective is to study the influence of the volume fraction $V_f$ and aspect ratio AR of nanofillers on the elastic properties of the composite. The inclusions are considered in a unidirectional and random orientation by using a computational method by Digimat-MF/FE and analytical approaches by Chamis, Hashin–Rosen and Halpin–Tsai. The results show that CNT- and GNP-reinforced nanocomposites have better performance than those without reinforcement. Additionally, by increasing the volume fraction and aspect ratio of nanofillers, Young’s modulus $E$ increases and Poisson’s ratio $\nu$ decreases. In addition, the composites have enhanced mechanical characteristics in the longitudinal orientation for CNT- reinforced polymer and in the transversal orientation for GNP-reinforced polymer. Full article

The objective of this paper is the vibroacoustic evaluation of an innovative material for a sports car roof, aiming at replacing fiberglass composite materials. Such evaluation was carried out using numerical and experimental analysis techniques, with cross-comparison between the corresponding results. The innovative material under analysis is a composite material, with a thermoplastic polypropylene matrix and reinforcement made of cellulose fibers. In order to validate the virtual dynamic modeling of the new material, the inertance on different points of some sheets made of the material under analysis was evaluated by an in-house made experimental activity, performed in the CRF (Fiat Research Center) test room, and cross-compared with corresponding results from a numerical analysis performed with the MSC Nastran software. Then, a realistic model of the car roof of the Alfa Romeo 4C car, made with the new material, was implemented and analyzed from the vibroacoustic point of view. The mere switch to the new material, with no changes in the geometry/structure of the car roof, did not allow preserving the original values of static rigidity, dynamic rigidity, and configuration of modal shapes. For this reason, a geometric/structural optimization of the component was performed. Once the new geometry/structure was defined, a vibroacoustic analysis was carried out, checking for a possible coupling between the fluid cavity modes and the structure car body modes. Finally, the vibroacoustic transfer functions to the driver’s ear node were assessed, considering two different excitation points on the structure. The excellent damping capacity of the proposed material led to an improvement in the vibroacoustic transfer functions and to a reduction in the weight of the pavilion. Full article

This work deals with the development of a new composite based on mortar reinforced with optimally sized alfa fiber (AF). Experimental investigations of physical and thermo-mechanical properties of the new AF mortar composite are performed for AF weight fraction varying from 0% to 5%. This simple material preparation process is described and scanning electron microscopy (SEM) is undertaken to analyze the morphology of this composite. It shows a random dispersion of the AF into the mortar matrix. Physical properties such as open porosity, water absorption, and bulk density fluctuations with AF mass content are measured. Measured thermal conductivity is compared to the values generated by different prediction models. Good agreement, within 9.6%, is obtained with data predicted by Woodside–Messmer’s method. It is demonstrated that this simple blending of AF into mortar improves significantly the thermo-mechanical behavior of the new composite. An addition of 5% of AF weight content makes composite material lighter by about 15%, enhances its insulating thermal capabilities by about 57% and increases its heat diffusion damping rate by about 49%. Moreover, the composite mechanical (flexural and compressive) strength increases by up to 10% for an AF weight content of 1%. Full article