Examinando por Autor "La Rubia, M.Dolores"
Mostrando 1 - 7 de 7
- Resultados por página
- Opciones de ordenación
Ítem Experimental and numerical analysis for the mechanical characterization of PETG polymers manufactured with FDM technology under pure uniaxial compression stress states for architectural applications(mdpi, 2020-09-25) Mercado-Colmenero, Jorge Manuel; La Rubia, M.Dolores; Mata-García, Elena; Rodríguez-Santiago, Moisés; Martín-Doñate, CristinaThis paper presents the numerical and experimental analysis performed on the polymeric material Polyethylene Terephthalate Glycol (PETG) manufactured with Fused Deposition Modeling Technology (FDM) technology, aiming at obtaining its mechanical characterization under uniaxial compression loads. Firstly, with the objective of evaluating the printing direction that poses a greater mechanical strength, eighteen test specimens were manufactured and analyzed according to the requirements of the ISO-604 standards. After that, a second experimental test analyzed the mechanical behavior of an innovative structural design manufactured in Z and X–Y directions under uniaxial compression loads according to the requirements of the Spanish CTE standard. The experimental results point to a mechanical linear behavior of PETG in X, Y and Z manufacturing directions up to strain levels close to the yield strength point. SEM micrographs show di erent structural failures linked to the specimen manufacturing directions. Test specimens manufactured along X present a brittle fracture caused by a delamination process. On the contrary, test specimens manufactured along X and Y directions show permanent plastic deformations, great flexibility and less strength under compression loads. Two numerical analyses were performed on the structural part using Young’s compression modulus obtained from the experimental tests and the load specifications required for the Spanish CTE standards. The comparison between numerical and experimental results presents a percentage of relative error of 2.80% (Z-axis), 3.98% (X-axis) and 3.46% (Y-axis), which allows characterizing PETG plastic material manufactured with FDM as an isotropic material in the numerical simulation software without modifying the material modeling equations in the data software. The research presented here is of great help to researchers working with polymers and FDM technology for companies that might need to numerically simulate new designs with the PETG polymer and FDM technology.Ítem Experimental and numerical study of the laser transmission welding between PA6/sepiolite nanocomposites and PLA(Elsevier, 2020-10-15) Moya-Muriana, José Ángel; Yebra-Rodríguez, África; Navas-Martos, Francisco J.; La Rubia, M.DoloresPA6/sepiolite nanocomposites have been manufactured at different wt% sepiolite loading and a fixed minimum load of a IR absorber additive (CAA). Nanocomposites were characterised and welded with PLA specimens through transmission laser welding technology (TLWT). Resulting welded specimens were also characterised. Experimental data obtained from the characterisations were introduced and processed in a Computer-Aided Engineering (CAE) software to obtain a suitable fracture model based on cohesive zone model (CZM) and capable of predicting the behaviour of the nanocomposite/PLA welds against shear forces. A correlation analysis was performed to assess the goodness of fit between the experimental and simulation data.Ítem Manufacture and characterisation of PLA biocomposites with high purity cellulose 1 isolated from olive pruning waste(Sage Journal, 2023-03-06) Rodríguez-Liébana, José A.; Navas-Martos, Francisco J.; Jurado-Contreras, Sofía; Morillas-Gutiérrez, Francisca; Mateo, Soledad; Moya, Alberto J.; La Rubia, M.DoloresA two-step chemical process was carried out on olive pruning residues according to an optimised sequence that led to the isolation of natural fibre with a high cellulose content. Reaction time, temperature and HNO3 concentration in the acid hydrolysis stage were optimised by means of the Response Surface Methodology to achieve the highest removal of hemicellulose and lignin and the highest crystallinity index, minimising cellulose hydrolysis. Subsequent hydrolysis with NaOH allowed to obtain a pulp enriched in cellulose (83.28 wt.%). Analysis revealed that the cellulose isolated had a high crystallinity index (70.06%) and thermal stability (Tmax = 357°C). The cellulose obtained was finally used for the manufacture of polymer biocomposites and to evaluate its viability as a filler for polymeric materials. The selected polymer matrix used was polylactic acid (PLA) and the amount of filler was 5 and 15% by weight, respectively. In general, the fibres did not improve the mechanical properties of PLA, and maintained unchanged its melting temperature. Microscopic analysis revealed that PLA/fibre adhesion was stronger for treated fibres. Contradictorily, the composites with untreated fibres presented slightly higher thermal stability. Water uptake increased with the concentration of fibres, being higher in those materials with untreated fibre.Ítem Manufacture and Characterization of Recycled Polypropylene and Olive Pits Biocomposites(MDPI, 2022-10-07) Jurado-Contreras, Sofia; Navas-Martos, Francisco; Rodríguez-Liébana, José A.; Moya, Alberto J.; La Rubia, M.DoloresThe present work studies the use of olive pit (OP) as a reinforcement in the manufacture of composites based on a post-consumer recycled polypropylene (rPP). In this way, it is feasible to provide added value from olive pits, a by-product resulting from the olive industry operations, while promoting the circular economy and reducing the use of fossil-based polymers. For this purpose, suitable samples were manufactured using 25 wt% and 40 wt% of OP. Additionally, the effect of incorporating additives was studied: (a) a process control additive (PA), and (b) a coupling agent of maleic anhydride grafted polypropylene (MAPP). The results showed an improvement in Young’s and flexural modulus with the OP addition. The incorporation of PA did not present any significant improvement in the properties of the materials, nevertheless it facilitated the biocomposite manufacturing process. As for the coupling agent, it significantly improved the mechanical properties, achieving the best results with the addition of the two types of additives and 40 wt% of OP. Moreover, the thermal properties were maintained, and there was an increase in crystallinity in all composites compared to rPP. According to the results of the fracture surface analysis, the coupling agent improves reinforcement-polymer matrix cohesion.Ítem Photo-oxidative degradation of injection molded sepiolite/polyamide66 nanocomposites(Elsevier, 2020-05) Fernández-Barranco, Cristina; Yebra-Rodríguez, África; Jiménez-Millán, Juan; Navas-Martos, Francisco Javier; Yebra, Ana; Koziol, A.E.; La Rubia, M.DoloresEvery day clay/polymer nanocomposites are included in more industrial applications, due to its high performance. Because of this, nanocomposites may be submitted to extreme conditions of work, which could degrade it. Exposure to solar radiation in the presence of oxygen (photo-degradation) represents one of the major problems of the Clay/Polymer anocomposites. In this study, samples of neat polyamide 66 (PA66-S-0) and reinforced nanocomposites with 1, 3, 5, 7 and 9 wt% organophilized sepiolite (PA66-S-1, PA66-S-3, PA66-S-5, PA66-S-7 and PA66-S-9 samples) are analysed after UV exposure, following the standard accelerated degradation method UNE-EN-ISO 4892-2. The aim of this study is to establish the effect of UV exposure on the mechanical, optical and crystallographic properties of the new material. Tensile tests show a reduction in the ductility and an embrittlement after degradation process. In addition, an increase of transparency is confirmed with the UV exposure. The carbonyl index in the samples containing sepiolite is lower than in neat PA66 whereas the yellowness index is not affected by degradation. Sepiolite has an inhibitor effect on the formation of C=O bonds. These results indicate that breaking of chains of PA66 starts in the amorphous region and that it is lower in the nanocomposites due to the low diffusion of oxygen induced by the sepiolite. This affirmation is corroborated by the obtained diffraction patterns.Ítem Production and characterization of cellulose acetate using olive tree pruning biomass as feedstock(Willey and sons, 2024-01-22) Rodríguez-Liébana, José Antonio; Robles-Solano, Esther; Jurado-Contreras, Sofia; Morillas-Gutiérrez, Francisca; Moya, Alberto J.; Mateo, Soledad; Navas-Martos, Francisco Javier; La Rubia, M.DoloresOlive tree pruning (OTP) is one of the most abundant sources of biomass waste in the Mediterranean basin. This is especially relevant in southern Spain where olive oil production represents a large part of the economy. Olive tree prunings are mostly either burned or are spread in olive orchards as an organic amendment, or used for heat generation on a domestic scale. However, the lignocellulosic composition of OTP makes it a potential source of biopolymers, thus providing an excellent economic alternative for the olive oil sector. In this work, pretreated OTP fibers were subjected to an optimized alkaline treatment followed by a single-step bleaching reaction with H2O2. Afterwards, the cellulose pulp was transformed chemically to obtain cellulose acetate. Noncellulosic components were removed effectively from OTP, thus obtaining a pulp highly purified in cellulose with 71% crystallinity and 355 °C maximum degradation temperature. Nevertheless, a very large amount of cellulose (ca. 50%) was eliminated throughout the process, especially during acid pretreatment, which was responsible for 38% solubilization. A similar level of acetylation and degree of substitution was obtained by using acetylation times in the range of 1 to 6 h. No large differences were observed in the infrared spectra and X-ray diffractograms of the synthesized acetates. However, their thermal stability varied significantly with reaction time, evolving from a multistep degradation pattern to a single and sharp peak between 300 and 400 °C with increasing time. Thermogravimetric curves revealed that at least 5 h (preferably 6 h) were needed to obtain cellulose acetate from OTP with adequate thermal stability for further processing.Ítem Using numerical-experimental analysis to evaluate rPET mechanical behavior under compressive stresses and MEX additive manufacturing for new sustainable designs(Emerald Publishing, 2023-07-26) Mercado-Colmenero , Jorge Manuel; La Rubia, M.Dolores; Mata-Garcia, Elena; Rodriguez-Santiago, Moises; Martin-Doñate, CristinaPurpose: Because of the anisotropy of the process and the variability in the quality of printed parts, finite element analysis is not directly applicable to recycled materials manufactured using fused filament fabrication. This study investigates the numerical-experimental mechanical behavior modeling of the recycled polymer rPET manufactured by MEX (Material Extrusion) process under compressive stresses for new sustainable designs. Design/Methodology: Forty-two test specimens were manufactured and analyzed according to the ASTM D695-15 standards. Eight numerical analyzes were performed on a real design manufactured with rPET using Young's compression modulus from the experimental tests. Finally, eight additional experimental tests under uniaxial compression loads were performed on the real sustainable design for validating its mechanical behavior versus computational numerical tests. Findings: As a result of the experimental tests, rPET behaves linearly until it reaches the elastic limit, along each manufacturing axis. The results confirmed the design's structural safety by the load scenario and operating boundary conditions. Experimental and numerical results show a difference of 0.001 mm to 0.024 mm, allowing for the rPET to be configured as isotropic in numerical simulation software without having to modify its material modeling equations. Practical implications: The results obtained are of great help to industry, designers, and researchers because they validate the use of recycled rPET for the ecological production of real-sustainable products using MEX technology under compressive stress and its configuration for numerical simulations. Major design companies are now using recycled plastic materials in their high-end designs. Originality: Validation results have been presented on test specimens and real ítems, comparing experimental material configuration values with numerical results. Specifically, no industrial or scientific work has been conducted with rPET subjected to uniaxial compression loads for characterizing experimentally and numerically the material using these results for validating a real case of a sustainable industrial product