Browsing by Author "Silva, F."
Now showing 1 - 8 of 8
Results Per Page
Sort Options
- An experimental study on recycling and reuse of pultruded composite material wastesPublication . Ribeiro, M.C.S; Meira Castro, Ana C.; Silva, F.; Fiúza, AntónioGlass fibre-reinforced plastics (GFRP) have been considered inherently difficult to recycle due to both: cross-linked nature of thermoset resins, which cannot be remoulded, and complex composition of the composite itself. Presently, most of the GFRP waste is landfilled leading to negative environmental impacts and supplementary added costs. With an increasing awareness of environmental matters and the subsequent desire to save resources, recycling would convert an expensive waste disposal into a profitable reusable material. In this study, efforts were made in order to recycle grinded GFRP waste, proceeding from pultrusion production scrap, into new and sustainable composite materials. For this purpose, GFRP waste recyclates, were incorporated into polyester based mortars as fine aggregate and filler replacements at different load contents and particle size distributions. Potential recycling solution was assessed by mechanical behaviour of resultant GFRP waste modified polymer mortars. Results revealed that GFRP waste filled polymer mortars present improved flexural and compressive behavior over unmodified polyester based mortars, thus indicating the feasibility of the GFRP industrial waste reuse into concrete-polymer composite materials.
- Eco-efficiency approaches towards a sustainable composite materials manufacturing industryPublication . Fiúza, António; Ribeiro, M. C. S.; Meira Castro, Ana C.; Silva, F.; Meixedo, JP; Alvim, M.R.; Oliveira, L.In this study the potential eco-efficiency performance of a pultrusion manufacturing company was assessed. Indicators values and eco-efficiency ratios were estimated taking into account the implementation of new proceedings and procedures in the production process of glass fibre reinforced polymers (GFRP) pultrusion profiles. Two different approaches were foreseen: 1)Adoption of a new heating system for pultrusion die in the manufacturing process, more effective and with minor heat losses; and 2) Recycling approach, with partial waste reuse of scrap material derived from manufacturing, cutting and assembly processes of GFRP profiles. These features lead to significant improvements on the sequent assessed eco-efficiency ratios of the present case study, yielding to a more sustainable product and manufacturing process of pultruded GFRP profiles.
- Improvement of Production Line in the Automotive Industry Through Lean PhilosophyPublication . Azevedo, J.; Sá, J.C.; Ferreira, Luís Pinto; Santos, G.; Cruz, F.M.; Jimenez, G.; Silva, F.This work refers to concepts and definitions of Lean Philosophy. The main targets were to study how waste reduction can be achieved on a production scenario, by identifying added-value operations, enhance productivity, levelling and over-processing reduction. The project behind this study is a massive one, which involves the installation of seven final production lines and more seven pre-assembly lines, being considered by the company, a project that must be as profitable as possible. After implementation and validation, costs were evaluated and the savings reached 10,9 % (2 159 000 €) considering all costs of industrialization.
- Influence of the operating temperature on the slow pyrolysis of pineconesPublication . Nascimento, M.; Silva, F.; Pilão, R.M.; Neto, M.P.; Ribeiro, A.M.This study investigated the production of biochars, bio-oils and non-condensable gas from pinecones through pyrolysis. The effect of temperature on the yields of the three phases and their characterization was studied. Char yield varied from 39.7 to 29.5 % and gas yield increased from 22.1 to 33.9 % as temperature rose from 408 to 661 ºC. Bio-oil yield increased from 38.3% at 408 ºC to 39.9 % at 562 ºC and then decreased to 36.6 % at 661 ºC. The chars obtained had an ash content between 1.38 and 2.20 %, volatiles in the range of 3.90 to 22.99 %, fixed carbon from 75.23 to 94.72 % and a higher heating value (HHV) in the range of 28.81 to 31.63 MJ.kg-1. The gas phase was mainly composed of carbon dioxide (CO2), carbon monoxide (CO), methane (CH4) and hydrogen (H2).
- Pirólise de agulhas de pinheiro: resultados preliminaresPublication . Nascimento, M.; Silva, F.; Pilão, R.; Neto, M.P.; Ribeiro, A.M.(Introdução) As florestas em Portugal ocupam uma área aproximada de 3 224 200 ha, apresentando como espécies predominantes o sobreiro, o pinheiro e o eucalipto (ICNF, 2021). Os pinheiros ocupam cerca de 28 % desta área e geram diversos resíduos, entre os quais as agulhas, que se não forem retiradas das florestas podem agravar o problema dos incêndios florestais (Omvesh et al., 2023). A energia proveniente de resíduos florestais pode ser transformada em combustíveis ou em outros produtos químicos através de processos termoquímicos, como a pirólise, onde há a formação de três fases distintas: o carbonizado, o bio-óleo e o gás (Basu, 2018).
- A Review of Heat Treatments on Improving the Quality and Residual Stresses of the Ti–6Al–4V Parts Produced by Additive ManufacturingPublication . Teixeira, Oscar; Silva, F.; Pinto Ferreira, Luís; Atzeni, EleonoraAdditive manufacturing (AM) can be seen as a disruptive process that builds complex components layer upon layer. Two of its distinct technologies are Selective Laser Melting (SLM) and Electron Beam Melting (EBM), which are powder bed fusion processes that create metallic parts with the aid of a beam source. One of the most studied and manufactured superalloys in metal AM is the Ti–6Al–4V, which can be applied in the aerospace field due to its low density and high melting point, and in the biomedical area owing to its high corrosion resistance and excellent biocompatibility when in contact with tissues or bones of the human body. The research novelty of this work is the aggregation of all kinds of data from the last 20 years of investigation about Ti–6Al–4V parts manufactured via SLM and EBM, namely information related to residual stresses (RS), as well as the influence played by different heat treatments in reducing porosity and increasing mechanical properties. Throughout the report, it can be seen that the expected microstructure of the Ti–6Al–4V alloy is different in both manufacturing processes, mainly due to the distinct cooling rates. However, heat treatments can modify the microstructure, reduce RS, and increase the ductility, fatigue life, and hardness of the components. Furthermore, distinct post-treatments can induce compressive RS on the part’s surface, consequently enhancing the fatigue life
- Valorisation of leather wastes from footwear industry via pyrolysis: Product yields and characterisationPublication . Silva, F.; Direito, D.; Pilão, R.; Ribeiro, A.M.(Objectives) The influence of temperature on the pyrolysis of leather trimmings from the footwear industry; Characterization of leather waste used in the pyrolysis process; The physical-chemical characterizations of biochar, bio-oil and non-condensable gases.
- Valorisation of Leather Wastes from the Footwear Industry via Pyrolysis: Product Yields and CharacterisationPublication . Silva, F.; Direito, D.; Pilão, R.; Ribeiro, A.M.; Silva, Felipe; Direito, Daniel; Pilão, Rosa Maria; Ribeiro, AlbinaThe footwear industry, although contributing positively to the Portuguese economy, generates a lot of residues including chromium tanned leather wastes. This study presents results on the slow pyrolysis of these residues at particle sizes between 5 and 6.3 mm and temperatures inside the reactor ranging from 444 to 875 °C. For this range of temperatures, char yield decreased from 36.2 to 28.1% and gas yield increased between 33.2 and 47.6%. The liquid phase yield was highest at 444 °C (30.6%) and then decreased to 24.3% at 875 °C. As the operating temperature increased, there was an increase in the ash content (15.8 to 21.6%) and a decrease in volatiles content (20.9–3.7%) of biochars. The higher heating values (HHV) of the chars were between 21.9 and 23.1 MJ/kg. Preliminary results show that an increase in particle size leads to a rise in char yield. The infrared analysis of the liquid phase indicated the presence of water, alcohols, phenols, carboxylic acids, alkanes, alkenes, and aromatics. The liquid phases had an average water content of 43%, densities between 1110 and 1120 kg/m3 and the HHV between 12.7 and 15.1 MJ/kg. The gases produced were analysed by gas chromatography. For 538 °C, the production of H2, CO, CH4 and CO2 was, respectively, 1.00, 0.37, 0.18 and 1.37 mol/kg of leather. At 875 °C, H2 was the most produced gas (2.74 mol/kg leather), followed by CO, CO2 and CH4 with quantities of 1.40, 1.26 and 0.42 mol/kg leather.