Papers by Pedro Henrique Poubel Mendonça da Silveira
Tecnologia em Metalurgia, Materiais e Mineração
Hematite (Fe 2 O 3 ), or ferric oxide, is a ceramic oxide that, despite being recognized in the f... more Hematite (Fe 2 O 3 ), or ferric oxide, is a ceramic oxide that, despite being recognized in the field of science and materials engineering, finds limited use as a sintering additive. Therefore, the purpose of this study was to explore the incorporation of hematite as a sintering additive in alumina (Al 2 O 3 ), employing conventional sintering at 1400 °C. Seven compositions were processed, with Fe 2 O 3 content varying from 0 to 8 wt.%. The samples underwent conventional ceramic processing steps (homogenization, drying, deagglomeration, sieving, and cold uniaxial pressing), followed by sintering at 1400 °C. The physical and mechanical properties of the produced samples were assessed through dilatometry, density measurement using the Archimedes' method, scanning electron microscopy with energy-dispersive spectroscopy (SEM/ EDS), and flexural and compression tests. The results revealed that the addition of 4 and 6 wt.% of Fe 2 O 3 resulted in reduced shrinkage of the ceramics, leading to low densification, highly porous surfaces, and diminished flexural strength. On the other hand, lower additions (0.5, 1, and 2 wt.%) of Fe 2 O 3 improved the sintering of Al 2 O 3 , yielding samples with increased flexural and compressive strength, linear shrinkage, and densification.
Materials research, 2024
Biocomposites have gained attention in the packaging industry due to their potential as sustainab... more Biocomposites have gained attention in the packaging industry due to their potential as sustainable alternatives to conventional synthetic materials. In this study, novel cotton incorporated poly (lactic acid)/ thermoplastic starch biocomposites were developed for packaging applications using in short shelf life products the extrusion method. Pelletized samples obtained by extrusion were stamped from plates obtained by compression and were characterized through measurement of density, hardness, contact angle and water absorption, as well as Fourier transform infrared spectroscopy (FTIR), thermal analysis and scanning electron microscopy (SEM). No significant changes in the density results were observed. A slight increase in the hardness of formulations in relation to the PLA was associated with the presence of cotton fiber in biocomposites. The FTIR results revealed physical interaction of PLA, TPS and cotton fiber. By DSC analysis, for all formulations the melting exhibited only one peak, suggesting good homogeneity and interaction among the components, as observed by TG/DTG results, and corroborating SEM analysis. The biocomposite PLA/TPS/Cotton 85/10/5 wt.% displayed greater increase in water absorption than both 95/5/0 and 90/5/5 wt.% formulations, which can be attributed to the increase in starch proportion, confirming the contact angle results. The hydrophilic tendency corroborated the biodegradation process in the packaging end-of-life.
Hungarian Journal of Industrial Chemistry, Oct 31, 2023
Ceramic matrix composites are widely studied in the ballistic sector due to their high hardness, ... more Ceramic matrix composites are widely studied in the ballistic sector due to their high hardness, fracture toughness, and improved ballistic performance in multilayer shielding systems. However, the presence of dopants in ceramics can pose challenges during processing and potentially compromise the final properties of the sintered material. This study focused on the ceramic processing of Al2O3-based ceramic matrix composites by adding 4 wt.% Nb2O5 (niobium oxide), 0.5 wt.% LiF (lithium fluoride), and 38.5 wt.% TiC (titanium carbide). The composites were produced using cold uniaxial pressing and conventional sintering at 1400 °C for 3 h. The composites were characterized using Archimedes' principle and scanning electron microscopy (SEM). The results revealed that the samples to which TiC was added exhibited low initial densities, indicating that the applied pressure of 50 MPa during cold pressing was insufficient to adequately densify the green bodies. Moreover, the presence of TiC led to a significant reduction in densification, making it challenging to apply a conductive coating for SEM analysis. Adjustments to the intensity of the electron beam were necessary to conduct the analysis successfully . Conversely, the samples to which TiC was not added exhibited high density values in the green state and yielded consistent results after sintering in line with previous research , indicating a satisfactory degree of sintering in the absence of TiC. These findings highlight the importance of carefully considering the addition of TiC in ceramic matrix composites during processing, which can have a significant impact on densification and subsequent material properties. The results contribute to the understanding of processing parameters with regard to the production of ceramic composites with desirable characteristics for ballistic applications.
Journal of Engineering Research, May 10, 2023
In this work, the unsaturated permeability of natural fibers of curaua, jute and raffia, arranged... more In this work, the unsaturated permeability of natural fibers of curaua, jute and raffia, arranged in the form of aligned fibers and woven in a flat style, was determined through the process of rectilinear resin infusion using a polyester resin as the working fluid. Fiber compressibility tests were previously carried out in order to study the effects of the vacuum level inside the infusion chamber on fiber compaction and to predict the porosity of fiber arrays. The effects on the permeability of the surface treatment of curaua fibers with NaOH at different concentrations were also studied. The results showed that raising the vacuum level, by changing the state of compaction of the fibers, reduced the overall permeability of all fibers and arrangements tested. The alkaline treatment of the curaua fibers contributed to the increase in the global permeability of the fabrics by reducing the permeability inside the fiber bundles.
Caracterização Química e Morfológica Do Tecido De Cânhamo Para Aplicações Em Compósitos De Engenharia
ABM Proceedings, Jun 1, 2022
Caracterização Termogravimétrica Do Compósitos De Matriz Epóxi Reforçada Com Tecido De Cânhamo Para Aplicações Em Engenharia
ABM Proceedings, Jun 1, 2022
Avaliação Da Resistência À Tração e Do Módulo De Elasticidade Do Compósito De Matriz Epóxi Reforçado Com Tecido De Cânhamo
ABM Proceedings, Jun 1, 2022
Comparação Da Densidade Da Fibra De Kenaf Através De Diferentes Técnicas
ABM Proceedings, Jun 1, 2022
Polymers, Sep 2, 2022
Several industry sectors have sought to develop materials that combine lightness, strength and co... more Several industry sectors have sought to develop materials that combine lightness, strength and cost-effectiveness. Natural lignocellulosic natural fibers have demonstrated to be efficient in replacing synthetic fibers, owing to several advantages such as costs 50% lower than that of synthetic fibers and promising mechanical specific properties. Polymeric matrix composites that use kenaf fibers as reinforcement have shown strength increases of over 600%. This work aims to evaluate the performance of epoxy matrix composites reinforced with kenaf fibers, by means of dynamicmechanical analysis (DMA) and ballistic test. Through DMA, it was possible to obtain the curves of storage modulus (E'), loss modulus (E") and damping factor, Tan δ, of the composites. The variation of E' displayed an increase from 1540 MPa for the plain epoxy to 6550 MPa for the 30 vol.% kenaf fiber composites, which evidences the increase in viscoelastic stiffness of the composite. The increase in kenaf fiber content induced greater internal friction, resulting in superior E". The Tan δ was considerably reduced with increasing reinforcement fraction, indicating better interfacial adhesion between the fiber and the matrix. Ballistic tests against 0.22 caliber ammunition revealed similar performance in terms of both residual and limit velocities for plain epoxy and 30 vol.% kenaf fiber composites. These results confirm the use of kenaf fiber as a promising reinforcement of polymer composites for automotive parts and encourage its possible application as a ballistic armor component.
Caracterização Da Fibra Natural De Kenaf
ABM Proceedings, Jun 1, 2022
Polymers
To complement previous results, an analysis of the chemical and morphological properties of babas... more To complement previous results, an analysis of the chemical and morphological properties of babassu fibers (Attalea speciosa Mart. ex Spreng.) was conducted in order to evaluate their potential as reinforcements in the production of composites with epoxy matrix. The diameter distribution was analyzed in a sample of one hundred fibers, allowing the verification of its variation. The determination of the chemical properties involved experimental analyses of the constituent index and X-ray diffraction. The diffractogram was used to calculate the crystallinity index and the microfibril angle, which are crucial parameters that indicate the consistency of the mechanical properties of babassu fibers and the feasibility of their use in composites. The results revealed that babassu fiber has a chemical composition, with contents of 28.53% lignin, 32.34% hemicellulose, and 37.97% cellulose. In addition, it showed a high crystallinity index of 81.06% and a microfibril angle of 7.67°. These cha...
Polymers
The search for unexplored natural materials as an alternative to synthetic components has driven ... more The search for unexplored natural materials as an alternative to synthetic components has driven the development of novel polymeric composites reinforced with environmentally-friendly materials. Natural lignocellulosic fibers (NLFs) have been highlighted as potential reinforcement in composite materials for engineering applications. In this work, a less known Amazonian fiber, the ubim fiber (Geonoma baculifera), is investigated as a possible reinforcement in epoxy composites and was, for the first time, thermally characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Additionally, its chemical structure was elucidated by Fourier transform infrared spectroscopy (FTIR). Ballistic tests were also performed against the threat of a 7.62 mm high-speed lead projectile. The results were statistically analyzed by the Weibull statistical analysis method. FTIR analysis showed the functional groups normally found for NLFs highly rich in cellulose, hemicel...
Polymers
Curaua, as a leaf-based natural fiber, appears to be a promising component with aramid fabric rei... more Curaua, as a leaf-based natural fiber, appears to be a promising component with aramid fabric reinforcement of hybrid composites. This work deals with the investigation of flexural, impact and elastic properties of non-woven curaua–aramid fabric hybrid epoxy composites. Five configurations of hybrid composites in a curaua non-woven mat with an increasing quantity of layers, up to four layers, were laminated through the conventional hand lay-up method. The proposed configurations were idealized with at least 60 wt% reinforcement in the non-alternating configuration. As a result, it was observed that the flexural strength decreased by 33% and the flexural modulus by 56%. In addition, the energy absorbed in the Charpy impact also decreased in the same proportion as the replaced amount of aramid. Through the impulse excitation technique, it was possible observe that the replacement of the aramid layers with the curaua layers resulted in decreased elastic properties. However, reduction m...
Avaliação Da Energia De Impacto Izod Dos Compósitos De Matriz Epóxi Reforçada Com Tecido De Cânhamo
ABM Proceedings
Polymers
Composites based on virgin and recycled polypropylene (PP and rPP) reinforced with 15 wt% sisal f... more Composites based on virgin and recycled polypropylene (PP and rPP) reinforced with 15 wt% sisal fibers, with and without alkali treatment, were prepared by compression molding in a mat composed of a three-layer sandwich structure. The sisal was characterized by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The composites were characterized according to physical and mechanical properties. Additionally, a factorial experimental design was used to statistically evaluate the mechanical properties of the composite. The FTIR and XRD indicated the partial removal of amorphous materials from the surface of the sisal after alkali treatment. The composites’ density results varied from 0.892 to 0.927 g·cm−3, which was in the desirable range for producing lightweight automotive components. A slight decrease in the hardness of the pure rPP and rPP composites in relation to the PP was observed. The water absorption was higher in rPP composites, regardless of the chem...
Eng
Auxetic structures (AXSs) are a novel class of materials with unique mechanical deformation behav... more Auxetic structures (AXSs) are a novel class of materials with unique mechanical deformation behavior associated with negative Poisson ratio. The combination of AXS configurations with various types of materials has unveiled a wide field of applications, including military high-velocity protection against explosions and ballistic projectiles. However, the characteristic geometric re-entrant model of AXSs imposes limitations and difficulties when using conventional manufacturing methods to assemble the structure lattice. Additive manufacturing (AM) has recently been explored as a more efficient and cost-effective method to fabricate AXSs, regardless of the type of material. This review paper focuses on the development and applications of AM processed AXSs. The review highlights the significance and great potential for this class of materials that can be produced relatively fast and at a low cost. The advantages of AXS/AM are expected to extend to important industrial sectors, particul...
Polymers
Basic properties of sedge fibers from the seven-islands-sedge plant (Cyperus malaccensis) were in... more Basic properties of sedge fibers from the seven-islands-sedge plant (Cyperus malaccensis) were investigated with possible application in reinforcing composite materials. A dimensional distribution and the effect of fiber diameter on density were investigated using gas pycnometry. The Weibull method, used to statistically analyze the acquired data from the diameter intervals, indicated an inverse dependence, where the thinnest fibers had the highest density values. The morphology of the fibers was obtained through scanning electron microscopy (SEM), in which a lower presence of defects was revealed in the thinner fibers, corroborating the inverse density dependence. In addition, the sedge fiber was characterized by differential scanning calorimetry and thermogravimetric analysis, which indicate an initial thermal degradation at around 241 °C. These results revealed for the first time that thinner sedge fibers might be promising reinforcement for polymer composites with a limit in tem...
Polymers
The growing concern about the limitation of non-renewable resources has brought a focus on the de... more The growing concern about the limitation of non-renewable resources has brought a focus on the development of environmentally sustainable and biodegradable composite materials. In this context, a trend in the development of natural fibers used as a reinforcement in composites is ever-increasing. In this work, for the first-time, fibers extracted from the seven-islands-sedge plant (Cyperus malaccensis) have been characterized by X-ray diffraction (XRD) to calculate the crystallinity index and the microfibrillar angle (MFA). Also, an evaluation of the ultimate tensile strength by diameter intervals has been investigated and statistically analyzed by both the Weibull method and the analysis of variance (ANOVA). Moreover, the maximum deformation and tensile modulus have been found from the data acquired. Pullout tests have been conducted to investigate the critical length and interfacial strength when sedge fibers, are incorporated into epoxy resin matrix. Microstructure analysis by sca...
Estudo Da Formação De Fases Por Difração De Raios X No Composto Cerâmico AL2O3-NB2O5-FE2O3
ABM Proceedings
Polymers
Several industry sectors have sought to develop materials that combine lightness, strength and co... more Several industry sectors have sought to develop materials that combine lightness, strength and cost-effectiveness. Natural lignocellulosic natural fibers have demonstrated to be efficient in replacing synthetic fibers, owing to several advantages such as costs 50% lower than that of synthetic fibers and promising mechanical specific properties. Polymeric matrix composites that use kenaf fibers as reinforcement have shown strength increases of over 600%. This work aims to evaluate the performance of epoxy matrix composites reinforced with kenaf fibers, by means of dynamic-mechanical analysis (DMA) and ballistic test. Through DMA, it was possible to obtain the curves of storage modulus (E′), loss modulus (E″) and damping factor, Tan δ, of the composites. The variation of E′ displayed an increase from 1540 MPa for the plain epoxy to 6550 MPa for the 30 vol.% kenaf fiber composites, which evidences the increase in viscoelastic stiffness of the composite. The increase in kenaf fiber cont...
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Papers by Pedro Henrique Poubel Mendonça da Silveira