- Braga, Braga, Portugal
Julio Viana
Universidade do Minho, Engenharia, Faculty Member
The present work details the experimental and numerical methodologies followed for a better characterization of the thermoelectric/thermomagnetic phenomena and the impact that these effects can have on the measurement conditions of highly... more
The present work details the experimental and numerical methodologies followed for a better characterization of the thermoelectric/thermomagnetic phenomena and the impact that these effects can have on the measurement conditions of highly sensitive measuring equipment's. It is, also, proposed a thermomagnetic numerical analysis procedure for the quantification of thermomagnetic perturbation phenomena, arising from applied thermal gradients, for potential use in the design of sensitive measuring systems towards the minimization of in-flight anomalies.
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Counter-flow injection molding (CF) is a novel two-component method which can be used for the production of parts with sandwich-like morphology. Compared to some established two-material techniques, CF can induce a higheroverall level of... more
Counter-flow injection molding (CF) is a novel two-component method which can be used for the production of parts with sandwich-like morphology. Compared to some established two-material techniques, CF can induce a higheroverall level of molecular orientation and hence an improved mechanical performance. The technique requires a two-component injection molding machine fitted with a special mold. The developed microstructure and mechanical properties of CF moldings are investigated in light of the applied set of processing conditions.
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The following paper presents a novel approach that can be applied to Operational Load Monitoring and Structural Health Monitoring processes. The approach is based on artificial intelligence (AI) and digital image correlation (DIC)... more
The following paper presents a novel approach that can be applied to Operational Load Monitoring and Structural Health Monitoring processes. The approach is based on artificial intelligence (AI) and digital image correlation (DIC) techniques. DIC is an optical method that allows measuring full-field structural displacements and strains. In the presented approach only a relatively small fragment of the material’s surface is monitored by DIC. The obtained partial image of strains or displacements is then processed by a carefully trained AI model, an image classification network, able to predict the state of whole structure (e.g. materials stresses, potential loss of material continuity). The assumption is that all possible load cases and states of the monitored structure can be identified and simulated, so the data obtained from simulations can then be used to train the image classification network. A numerical example is presented as proof of the presented concept. A modern lightweig...
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Fundacao para a Ciencia e a Tecnologia (FCT) - FRH/BD/42922/2008, MIT-Pt/EDAM-EMD/0007/2008
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In this paper we present an alternative fabrication method based on polymeric materials and technologies for three-axis thermal accelerometers. The device is composed by four microinjected parts forming an external structure responsible... more
In this paper we present an alternative fabrication method based on polymeric materials and technologies for three-axis thermal accelerometers. The device is composed by four microinjected parts forming an external structure responsible for the coupling and sealing of a polymeric membrane. The membrane contains and protects the heater and thermoresistors and is fabricated by microtechnologies. The fabrication process was successful although some issues were noticed in the mould during the microinjection process. Regarding the ejection side, a redesign was done to first assure the locking of the micro-parts on the movable side of the mould and second to improve the extraction of the parts avoiding its deformation. Overheating of the mould and polymer freezing on the injection nozzle were the main issues found on the injection side of the mould. Three different injection nozzle designs and two different fabrication materials were analyzed and simulated. The results show that an interm...
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This work attempts to contribute to bridge the gap between scientific challenges and industrial stakes regarding PP/nanoclay composites. Pieces of nanocomposites were obtained by direct injection of commercial PP mixed with a commercial... more
This work attempts to contribute to bridge the gap between scientific challenges and industrial stakes regarding PP/nanoclay composites. Pieces of nanocomposites were obtained by direct injection of commercial PP mixed with a commercial MB of PP with 50% of organoclay, with a double-gated hot runner mould, which produced mouldings with a weld line. The moulding microstructure was assessed by POM and XRD, while the distribution and exfoliation grade of clay was evaluated by TEM and XRD. The typical skin-core structure was found, with a skin thickness wider in bulk than in weld line zones. Regarding clay platelets mostly intercalated structures were seen. The impact properties at room temperature were assessed by means of tensile and biaxial tests. Properties were monitored at different sites of the mouldings. At the weld line zone less energy was consumed under tensile conditions and exhibited higher apparent impact toughness under biaxial conditions than the bulk zone. Visual inspec...
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Carbon nanotubes (CNTs) are one of the most promising materials in sensing applications due to their electrical and mechanical properties. This paper presents a comparative study between CNT Buckypaper (BP) and aligned CNT-based strain... more
Carbon nanotubes (CNTs) are one of the most promising materials in sensing applications due to their electrical and mechanical properties. This paper presents a comparative study between CNT Buckypaper (BP) and aligned CNT-based strain sensors. The Buckypapers were produced by vacuum filtration of commercial CNTs dispersed in two different solvents, N,N-Dimethylformamide (DMF) and ethanol, forming freestanding sheets, which were cut in 10 × 10 mm squares and transferred to polyimide (PI) films. The morphology of the BP was characterized by scanning electron microscopy (SEM). The initial electrical resistivity of the samples was measured, and then relative electrical resistance versus strain measurements were obtained. The results were compared with the knocked-down vertically aligned CNT/PI based sensors previously reported. Although both types of sensors were sensitive to strain, the aligned CNT/PI samples had better mechanical performance and the advantage of inferring strain dire...
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Organic photovoltaic (OPV) devices, made with semiconducting polymers, have recently attained a power conversion efficiency (PCE) over 14% in single junction cells and over 17% in tandem cells. These high performances, together with the... more
Organic photovoltaic (OPV) devices, made with semiconducting polymers, have recently attained a power conversion efficiency (PCE) over 14% in single junction cells and over 17% in tandem cells. These high performances, together with the suitability of the technology to inexpensive large-scale manufacture, over lightweight and flexible plastic substrates using roll-to-roll (R2R) processing, place the technology amongst the most promising for future harvesting of solar energy. Although OPVs using non-fullerene acceptors have recently outperformed their fullerene-based counterparts, the research in the development of new fullerenes and in the improvement of the bulk-heterojunction (BHJ) morphology and device efficiency of polymer:fullerene solar cells remains very active. In this review article, the most relevant research works performed over the last 3 years, that is, since the year 2016 onwards, in the field of fullerene-based polymer solar cells based on the copolymers PTB7, PTB7-Th...
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A polymeric microinjected 3-axis thermal accelerometer is presented in this paper. The device has two main components: a polymer encapsulation body composed by two pairs of microparts and polymeric membranes. The membranes are supporting... more
A polymeric microinjected 3-axis thermal accelerometer is presented in this paper. The device has two main components: a polymer encapsulation body composed by two pairs of microparts and polymeric membranes. The membranes are supporting the active elements (temperature sensors and heater). The accelerometer requires detailed specifications for the design, mould machining and polymer selection. The encapsulation body is made of polystyrene due to the high MFI (melt flow index) and low coefficient of thermal expansion required for microinjection moulding. The final design consists in a set of two different mouldings, enabling an easy coupling and dimensions bellow 500 micrometer. A conventional type of mould was entirely designed for the device. The mould structure is made of steel 1.1730 while the inserts were machined in steel 1.2311 indicated for compression. A draft angle of 2% was machined for the machined for the runner system while the moulding zones have no draft angle but they were over dimensioned (0.45%) to account for the material shrinkage in order to obtain the micro parts with the desired dimensions. Microparts were moulded using a Boy 12A/M micromoulding machine (mould temperature of 60ºC, polymer temperature ranges between 190- 240ºC and a cycle time of 42 seconds) and the manufactured microparts are within the tolerances required for the application.Fundação para a Ciência e a Tecnologia (FCT
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A completely new approach for the fabrication of 3-axis thermal accelerometers is presented in this paper. Microinjected polystyrene micro-parts are assembled with active polyimide membranes enabling the construction of an innovative... more
A completely new approach for the fabrication of 3-axis thermal accelerometers is presented in this paper. Microinjected polystyrene micro-parts are assembled with active polyimide membranes enabling the construction of an innovative polymer based thermal accelerometer. The use of polymers (polystyrene and polyimide) with low thermal conductivities improves the overall power consumption of the thermal accelerometer and enables a simple and low-cost fabrication process (no clean room infrastructure required).Fundação para a Ciência e a Tecnologia (FCT) - PTDC/EEA-ELC/099834/2008
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Purpose: Paper summarizes and focus on investigation of PP/MMT nanocomposite in mechanical and statistical
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The fracture behavior of polypropylene reinforced with different amounts of PP/50% organoclay masterbatch was studied. Test pieces were prepared using a two-gated hot runner injection mould. Morphology of final pieces was analyzed by... more
The fracture behavior of polypropylene reinforced with different amounts of PP/50% organoclay masterbatch was studied. Test pieces were prepared using a two-gated hot runner injection mould. Morphology of final pieces was analyzed by polarized optical microscopy, Xray diffraction and transmission electron microscopy. Fracture toughness was evaluated under quasi-static conditions at different positions in the molded pieces. The brittle mode of failure of PP became more ductile with increasing the amount of clay. However, the midthickness region (core) of “ductile” samples underwent brittle fracture while the surface layers (skin) behave in a ductile way, exhibiting elongation, necking and ductile tearing, probably due to differences in thickness and crystalline structure found in skin layers of composite pieces. Different Fracture Mechanics approaches were applied to characterize the fracture behavior: fracture toughness initiation value was assessed by means of the stress intensity ...
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Neste artigo, foi estudada a moldação por injecção de polímeros incompatíveis. Para tal foram usadas duas técnicas de moldação multimaterial, sobre-injecção e co-injecção mono-sandwich. Estudou-se o efeito das condições de processamento e... more
Neste artigo, foi estudada a moldação por injecção de polímeros incompatíveis. Para tal foram usadas duas técnicas de moldação multimaterial, sobre-injecção e co-injecção mono-sandwich. Estudou-se o efeito das condições de processamento e do uso de aditivos compatibtlizadores na adesão de polímeros moldados. O estuddo mostra que. para a técnica de sobre-injecçâo, mudando as condições de processamento, tais como as temperaruras do fundido e do molde, é possível aumentar a adesão entre os dois polímeros. Para a co-injeçcao mono-sandwich, a incorporação de pequenas quantidades de um agente compatibilizador, tais como nanoargilas e SEBS (esbreno-elitello-butadieno-esllreno), aumentam a adesão entre polímeros. As nanoargllas são mais eficientes para temperaturas do fundido mais baixas, enquanto SEBS melhora a adesão a temperaturas mais altas.ln this paper the moulding of incompatible polymers is studied. Two different multi-material techniques were used: overmoulding and mono-sandwich. T...
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Recently, carbon nanotubes (CNTs) thin films have been widely applied in sensing applications due to their piezoresistive response. Furthermore, CNT anisotropic electric properties, due to its alignment, can provide useful information... more
Recently, carbon nanotubes (CNTs) thin films have been widely applied in sensing applications due to their piezoresistive response. Furthermore, CNT anisotropic electric properties, due to its alignment, can provide useful information regarding strain direction. We present a comparative study between knocked down vertically aligned CNT based sensor, reported in our previous work [1], and CNT bucky papers (BP) based sensors. For this purpose, commercial multi-wall carbon nanotubes (MWCNTs) were dispersed in two different solvents, dimethylformamide (DMF) and ethanol, vacuum filtrated and dried. From these freestanding BP thin films, 10x10 mm squares were cut off and transferred to polyimide (PI) films. The relative electric resistance response and sensitivity of the strained samples was measured and compared with the knocked down CNT/PI based sensor. Moreover, the morphology of the samples was characterized by scanning electron microscopy (SEM). The results showed a high sensitivity ...
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Carbon Fibre Reinforced Polymers (CFRP) have been widely used in advanced markets, such as, the aeronautic, aerospace and military ones. Despite their extraordinary mechanical properties and low density, advanced composites, due to their... more
Carbon Fibre Reinforced Polymers (CFRP) have been widely used in advanced markets, such as, the aeronautic, aerospace and military ones. Despite their extraordinary mechanical properties and low density, advanced composites, due to their intrinsic brittleness and layer-by-layer nature, present some vulnerability when submitted to impact, dynamic and flexural loading. Low velocity impacts (LVI) are one of the most dangerous events that composite laminate can face in their life time. These solicitations may develop imperceptible internal laminate damages, namely delaminations, that tend of propagate in service, compromising part performance. In order to improve interlaminar crack propagation, some works were already carried out using interleaved thin veils between laminate layers to enhance the interlaminar Mode I and II fracture toughness. In this work, a study was carried out on the distribution of stresses across the thickness of a carbon/epoxide laminate typically used in structur...
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Multifunctional composites for deformation sensing applications have been developed by solvent casting based on polycarbonate (PC) and polylactic acid (PLA) reinforced with carbon nanotubes (CNT). Composites shows homogeneous filler... more
Multifunctional composites for deformation sensing applications have been developed by solvent casting based on polycarbonate (PC) and polylactic acid (PLA) reinforced with carbon nanotubes (CNT). Composites shows homogeneous filler dispersion and low percolation threshold at 0.1 and 0.06 wt% CNT content for PLA and PC, respectively. The maximum electrical conductivity obtained for the larger filler contents is two order of magnitude higher for PLA composites than for PC ones, showing that the matrix influences the electrical properties of the composites. With respect to the mechanical characteristics, the samples show a maximum strain near 40% and 2.75% for composites with 0.25 and 1 wt% CNT content for PC and PLA, respectively, decreasing for larger filler contents. Concerning the piezoresistive response, 4‐point‐bending experiments from 0.1 to 5 mm, lead to a Gauge Factor (GF) of ≈1 for PC, showing that the piezoresistive response if determined by the geometrical response. On the other hand, PLA composites show GF of ≈3, revealing also intrinsic contributions, due to the variation of the filler network upon material deformation. The resistance variation upon mechanical bending deformation shows linear response for the composites near the percolation threshold and above, for both composites. A proof‐of‐concept of the functional sensing response for applications is achieved by measuring the bending deformation of an endoscope, showing that the developed sensors can determine the bending orientation and intensity, as predicted by the simulation model applied to the endoscopeThis work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2020 and projects UIDB/05549/2020 and TSSiPRO-NORTE-01-0145-FEDER-000015. The authors thank the FCT for financial support under SFRH/BPD/110914/2015 (P.C.) and SFRH/BD/110622/2015 (S.G.) grants. Financial support was taken from the Basque Government Industry and Education Departments under the ELKARTEK, HAZITEK, and PIBA (PIBA-2018-06) programs. Technical and human support provided by SGIker (UPV/EHU, MICINN, GV/EJ, EGEF, and ESF) is gratefully acknowledged
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ABSTRACT In this work we present the thermal characterization of the full scope of polyhydroxyalcanoate and poly(lactic acid) blends obtain by injection molding. Blends of polyhydroxyalcanoate and poly(lactic acid) (PHA/PLA) were prepared... more
ABSTRACT In this work we present the thermal characterization of the full scope of polyhydroxyalcanoate and poly(lactic acid) blends obtain by injection molding. Blends of polyhydroxyalcanoate and poly(lactic acid) (PHA/PLA) were prepared in different compositions ranging from 0–100% in steps of 10%. The blends were injection molded and then characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and wide angle X-ray diffraction (WAXD). The increment of PHA fraction increased the degree of crystallinity of the blend and the miscibility of the base polymers as verified by the Fox model. The WAXD analysis indicates that the presence of PHA hindered the PLA crystallization. The crystallization evolution trough PHA weight fraction (wf) shows a phase inversion around 50-60%. SEM analyses confirmed that the miscibility of PHA/PLA blends increased with the incorporation of PHA and became total for values of PHA higher that 50%.
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In this work, the mechanical behavior of polyhyroxyalkanoate (PHA)/poly(lactic acid) (PLA) blends is investigated in a wide range of compositions. The mechanical properties can be optimized by varying the PHA contents of the blend. The... more
In this work, the mechanical behavior of polyhyroxyalkanoate (PHA)/poly(lactic acid) (PLA) blends is investigated in a wide range of compositions. The mechanical properties can be optimized by varying the PHA contents of the blend. The flexural and tensile properties were estimated by different models: the rule of mixtures, Kerner–Uemura–Takayanagi (KUT) model, Nicolai–Narkis model and Béla–Pukánsky model. This study was aimed at investigating the adhesion between the two material phases. The results anticipate a good adhesion between both phases. Nevertheless, for low levels of incorporation of PHA (up to 30%), where PLA is expectantly the matrix, the experimental data seem to deviate from the perfect adhesion models, suggesting a decrease in the adhesion between both polymeric phases when PHA is the disperse phase. For the tensile modulus, a linear relationship is found, following the rules of mixtures (or a KUT model with perfect adhesion between phases) denoting a good adhesion ...
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Carbon fibre reinforced polymers (CFRP) are widely used in advanced applications due to their high performance and low weight. However, when exposed to some conditions, as shear, dynamic and impact loading, they may develop interlaminar... more
Carbon fibre reinforced polymers (CFRP) are widely used in advanced applications due to their high performance and low weight. However, when exposed to some conditions, as shear, dynamic and impact loading, they may develop interlaminar damages. One of the most common and dangerous solicitations that they must face in service is low velocity impact (LVI) events. To improve damage tolerance to LVI events, three new bioinspired CFRP laminates were developed and tested in the present work to assess and compare their behaviour to the one presented by a typical aeronautic standard laminate. All these studied laminates, having approximately the same thickness of 4 mm, were produced by vacuum bag infusion and observed under reflexion and scanning electron microscopes (SEM) for assessing their processing quality. Interlaminar shear strength (ILSS) and LVI tests were performed in order to evaluate their delamination resistance and impact response. LVI tests were performed for all laminates a...
The cooling process in polymer injection molding is of great importance as it has a direct impact on both productivity and product quality. In this paper a Multi-objective Optimization Genetic Algorithm, denoted as Reduced Pareto Set... more
The cooling process in polymer injection molding is of great importance as it has a direct impact on both productivity and product quality. In this paper a Multi-objective Optimization Genetic Algorithm, denoted as Reduced Pareto Set Genetic Algorithm with Elitism (RPSGAe), was applied to optimize both the position and the layout of the cooling channels in the injection molding process. The optimization model proposed in this paper is an integration of genetic algorithms and Com-puter-Aided Engineering, CAE, technology applied to polymer process simulations. The main goal is to implement an auto-matic optimization scheme capable of defining the best posi-tion and layout of the cooling channels and/or setting the processing conditions of injection moldings. In this work the methodology is applied to an L-shape molding with the aim of minimizing the part warpage quantified by two different con-flicting measures. The results produced have physical meaning and correspond to a successful...
Historia del artículo: Recibido 5 de Junio 2019 En la versión revisada 15 de Junio 2019 Aceptado 5 de Julio 2019 Accesible online 15 de Enero 2020 Los polímeros reforzados con fibra de carbono (CFRP) han sido ampliamente utilizados en... more
Historia del artículo: Recibido 5 de Junio 2019 En la versión revisada 15 de Junio 2019 Aceptado 5 de Julio 2019 Accesible online 15 de Enero 2020 Los polímeros reforzados con fibra de carbono (CFRP) han sido ampliamente utilizados en mercados avanzados, como los aeronáuticos, aeroespaciales y militares. Y aunque presentan extraordinarias propiedades mecánicas y baja densidad, los compósitos avanzados presentan cierta vulnerabilidad cuando se someten al impacto, a la carga dinámica y a la flexión, debido principalmente a su fragilidad intrínseca y a su naturaleza capa por capa. Los impactos de baja velocidad (LVI) son uno de los fenómenos más peligrosos a los que un compósito laminado puede enfrentarse en su vida útil. Estos impactos pueden producir daños laminares internos imperceptibles, como por ejemplo, delaminaciones que tienden a propagarse durante el uso de los materiales comprometiendo por tanto el rendimiento de la pieza.
The understanding and interpretation of the macroscopic mechanical behaviour of polymers require the monitoring of the morphology evolution during deformation spaning several scale-lengths. This multi-scalelength approach enabled the... more
The understanding and interpretation of the macroscopic mechanical behaviour of polymers require the monitoring of the morphology evolution during deformation spaning several scale-lengths. This multi-scalelength approach enabled the identification of deformation processes, intensively studied for semicrystalline polymers (e.g., polyolefins) [1-4], mainly for simple initial microstructural states (spherulite or highly oriented structures). The availability of synchrotron X-ray sources allowed the study of complex morphological changes during deformation at relative high strainrates, by collecting time-resolved simultaneous WAXS and SAXS and stress-strain data [1, 4]. This enables the correlation of the evolution of the crystalline phase features to the macroscopic behaviour. Recently, Davies et al combined tensile testing and synchrotron radiation WAXS to investigate the morphology changes during deformation of polypropylene with different thermal treatments[4].
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Permanently implanted sensors with continuous monitoring of pressure for cardiovasc lar applications are particularly attractive as they provide additional opportunities for better therapies and enhanced quality of life. In Abdominal... more
Permanently implanted sensors with continuous monitoring of pressure for cardiovasc lar applications are particularly attractive as they provide additional opportunities for better therapies and enhanced quality of life. In Abdominal Aortic Aneurysms (AAAs), where stentgrafts are frequen ly used for treatment, are exemplary applications f or this type of device. This paper introduces a new carbon nanotube (CNT)-based flexible capacitive sensor along with two different reading based on inductive-coupling. The fabrica for the flexible sensor and the main characteristics of the reading systems are presented , as well as tion results and preliminary experimental results of CNT-PDMS elements. Electrical conductivity of PDMS membranes with embedded aligned CNTs is 10 S/m, in the direction perpendicular to the CNT axis.
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In this paper the effect of the inclusion of thermotropic liquid crystalline polymers (TLCP) in thermoplastic polymers is analyzed, with due attention to similar studies reported in the literature. Numerous results relative to TLCP... more
In this paper the effect of the inclusion of thermotropic liquid crystalline polymers (TLCP) in thermoplastic polymers is analyzed, with due attention to similar studies reported in the literature. Numerous results relative to TLCP containing blends are considered in terms of structure development in typical processing operations like extrusion and fiber spinning. Several systems have been studied in order to emphasize that different effects can be obtained as regards processing and mechanical properties of the host matrices. As for rheological aspects, it has been verified that TLCP can be considered as effective flow aids, even at low concentrations. The addition of a low percentage (5 to 10 %) of a TLCP with a viscosity lower than that of the matrix produces a significant reduction (25 to 40 %) in the blend viscosity. Moreover, mechanical results have shown that an improvement of the matrix rigidity can be obtained, especially at high percentages of TLCP (30 %), under processing ...
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ABSTRACT: The use of commercially available injection moulding simulation software’s allows us to predict the process response to the operating conditions defined. These codes can be used to define better injection conditions to use in... more
ABSTRACT: The use of commercially available injection moulding simulation software’s allows us to predict the process response to the operating conditions defined. These codes can be used to define better injection conditions to use in specific situations, i.e., to optimize the process. Generally, this is an iterative procedure requiring the analysis of multiple outputs (pressures, temperatures, shear stresses profiles) supported by pre-established decision criteria. Most of the cases the taken options may lead to opposed results. In this sense the development of optimization methodologies are of paramount importance in order to facilitate the definition of processing windows in injection moulding. In this work the results obtained by the use of an automatic optimization methodology based on Multi-Objective Evolutionary Algorithms (EMOA), where an EMOA is linked to an injection moulding simulation code (CMOLD), will be assessed experimentally. For that purpose the processing conditi...
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Page 1. Fiber Orientation in Divergent/Convergent Flows in Expansion and Compression Injection Molding Cristina A. Silva, Ju´ lio C. Viana, Ferrie WJ van Hattum, Anto´ nio M. Cunha IPC Institute for Polymers and Composites ...
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A indústria mundial de componentes interiores de portas para a Industria Automóvel encontra-se constantemente a optimizar a relação preço/qualidade para se manter competitiva no mercado. Ultimamente, com a crescente importância dos... more
A indústria mundial de componentes interiores de portas para a Industria Automóvel encontra-se constantemente a optimizar a relação preço/qualidade para se manter competitiva no mercado. Ultimamente, com a crescente importância dos materiais obtidos através de fontes renováveis, e a biodegradabilidade do material no fim-de-vida do produto impulsionam uma viragem nos materiais para aplicações na indústria automóvel. Uma das possibilidades é a utilização de polímeros obtidos a partir de fontes naturais renováveis e biodegradáveis - como por exemplo o Polilactato (PLA) e o poli(hidroxialcanoato) (PHA) - em lugar dos polímeros de origem petrolífera – p.e., Polipropileno (PP), Polietileno (PE) ou Acrilo-Butano-Estireno (ABS).
Dado que a indústria necessita de uma boa relação preço/qualidade, e que essa qualidade se traduz inicialmente pelo cumprimento dos requisitos de serviço, torna-se necessário encontrar alternativas que satisfaçam os requisitos técnicos, como por ex: temperatura de serviço, propriedades mecânicas, estabilidade dimensional, aspecto estético, entre outras. Do universo dos polímeros biodegradáveis e de origem natural, o PHA é aquele que apresenta melhores propriedades prevendo-se ser capaz de cumprir esses requisitos. No entanto, e devido ao seu actual elevado preço, a solução não é economicamente viável. Sendo necessário baixar o preço do polímero final para que a eco-solução se torne competitiva. Uma das possíveis soluções é a mistura com polímeros biodegradáveis mais baratos, como o PLA. Por outro lado, o PHA pode também reforçar o PLA, conferindo-lhe uma maior tenacidade.
Neste artigo iremos estudar o comportamento mecânico de várias misturas de PLA/PHA a fim de podermos concluir qual o rácio PLA/PHA que, preenchendo os requesitos mínimos de serviço, nos apresenta um menor custo, ou uma melhor relação qualidade/preço.
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Dado que a indústria necessita de uma boa relação preço/qualidade, e que essa qualidade se traduz inicialmente pelo cumprimento dos requisitos de serviço, torna-se necessário encontrar alternativas que satisfaçam os requisitos técnicos, como por ex: temperatura de serviço, propriedades mecânicas, estabilidade dimensional, aspecto estético, entre outras. Do universo dos polímeros biodegradáveis e de origem natural, o PHA é aquele que apresenta melhores propriedades prevendo-se ser capaz de cumprir esses requisitos. No entanto, e devido ao seu actual elevado preço, a solução não é economicamente viável. Sendo necessário baixar o preço do polímero final para que a eco-solução se torne competitiva. Uma das possíveis soluções é a mistura com polímeros biodegradáveis mais baratos, como o PLA. Por outro lado, o PHA pode também reforçar o PLA, conferindo-lhe uma maior tenacidade.
Neste artigo iremos estudar o comportamento mecânico de várias misturas de PLA/PHA a fim de podermos concluir qual o rácio PLA/PHA que, preenchendo os requesitos mínimos de serviço, nos apresenta um menor custo, ou uma melhor relação qualidade/preço.
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The best way to obtain cellulosic fibers is to use the pulp wastes from the paper plants. The pre-processing of the fibers is a very complex and chemically heavy set of operations. At the end a small part of the fibers will be rejected... more
The best way to obtain cellulosic fibers is to use the pulp wastes from the paper plants.
The pre-processing of the fibers is a very complex and chemically heavy set of operations. At the end a small part of the fibers will be rejected and removed from the production system. Actually these rejected fibers are being incinerated at the furnace that dries the raw-wood. This means that after a set of chemical treatments, that ends with a bleach, the fibers will be incinerated driving to a waste of money, once that all the effort applied to the treatment are not useful, and by other side, the incineration can release some non-healthy emissions.
Is possible to use these rejected fibers on composite applications where there mechanical properties can improve the matrix.
We will present the study of the incorporation of these rejected fibers into a biodegradable PLA and PHA blended matrix to replace, in some applications, the petrol-based polymers used into the automotive interior trims.
The mechanical, and thermal properties will be assess and compared, with the properties of the petrol-polymers used normally in this type of applications.
At the end it will be presented some concrete applications studied during this work.
The pre-processing of the fibers is a very complex and chemically heavy set of operations. At the end a small part of the fibers will be rejected and removed from the production system. Actually these rejected fibers are being incinerated at the furnace that dries the raw-wood. This means that after a set of chemical treatments, that ends with a bleach, the fibers will be incinerated driving to a waste of money, once that all the effort applied to the treatment are not useful, and by other side, the incineration can release some non-healthy emissions.
Is possible to use these rejected fibers on composite applications where there mechanical properties can improve the matrix.
We will present the study of the incorporation of these rejected fibers into a biodegradable PLA and PHA blended matrix to replace, in some applications, the petrol-based polymers used into the automotive interior trims.
The mechanical, and thermal properties will be assess and compared, with the properties of the petrol-polymers used normally in this type of applications.
At the end it will be presented some concrete applications studied during this work.
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"The word automotive industry of interior door trims is constantly optimizing the relation price/quality to gain competitive in the market. Nowadays, the importance of biodegradable polymers or polymers from renewable sources is... more
"The word automotive industry of interior door trims is constantly optimizing the relation price/quality to gain competitive in the market. Nowadays, the importance of biodegradable polymers or polymers from renewable sources is increasing. This type of polymers allied to the life-cycle-analysis is making a turn over into the automotive industry.
One possibility is the use into the interior door trims of biodegradable polymers from renewable sources – such as Poly-lactic Acid (PLA) and Poly-Hidroxyalcanoate (PHA) – instead of the tradicional petro-source polymers – such as Polypropylene (PP), Polyethylene (PE) or Acryl-Butadiene-Styrene (ABS).
Once that the relation price/quality is a primordial relation into the automotive industry and that the quality starts to be the fulfillment of the service requirements, it’s mandatory to find alternatives that fulfill the technical specifications- such as Service Temperature, Mechanical Behavior, Dimensional Stability among others.
From the universe of biodegradable polymers from natural sources, the PHA is the one that has better properties and is expected to be able to fulfill these requirements. However, due to its actual price, the solution isn’t economically viable. To make the eco-solution competitive is necessary to reduce the price of the final polymer. One way is to blend it with more cheap polymers such as PLA."
One possibility is the use into the interior door trims of biodegradable polymers from renewable sources – such as Poly-lactic Acid (PLA) and Poly-Hidroxyalcanoate (PHA) – instead of the tradicional petro-source polymers – such as Polypropylene (PP), Polyethylene (PE) or Acryl-Butadiene-Styrene (ABS).
Once that the relation price/quality is a primordial relation into the automotive industry and that the quality starts to be the fulfillment of the service requirements, it’s mandatory to find alternatives that fulfill the technical specifications- such as Service Temperature, Mechanical Behavior, Dimensional Stability among others.
From the universe of biodegradable polymers from natural sources, the PHA is the one that has better properties and is expected to be able to fulfill these requirements. However, due to its actual price, the solution isn’t economically viable. To make the eco-solution competitive is necessary to reduce the price of the final polymer. One way is to blend it with more cheap polymers such as PLA."
"The Mechanical properties of PHA/PLA blends can be optimized trough the variation of the PHA contents on the blend. It’s possible to predict the flexural and tensile properties recurring to Rule of Mixtures, Kerner–Uemura–Takayanagi,... more
"The Mechanical properties of PHA/PLA blends can be optimized trough the variation of the PHA contents on the blend.
It’s possible to predict the flexural and tensile properties recurring to Rule of Mixtures, Kerner–Uemura–Takayanagi, Nicolai-Narkis and Béla-Pukánsky models. All of them will validate the experimental obtain values and they anticipate a good adhesion between both phases.
Nevertheless, for low levels of incorporation of PHA (up to 30%), where PLA is expectantly the matrix, the experimental data seems to deviate from the perfect adhesion models, suggesting a decrease on the adhesion between both polymeric phases.
The impact energy varies over 157% over the entire blend composition. It’s possible to identify that for blends with PHA weight fraction lower than 50% the impact strength of the blend is higher than the pure base polymers. The highest synergetic effect is found for the blend PHA/PLA of 30/70. The second maximum is found for the inverse composition.
PLA has a Heat Deflection Temperature substantially lower than PHA. For the blends, the HDT increases with the increment upon the % of incorporation of PHA. Up to 50% PHA (PLA as matrix), the HDT is practically constant and equal to PLA value. Over this point (PHA matrix), the HDT of the polymer blends increases linearly with % of addition of PHA."
It’s possible to predict the flexural and tensile properties recurring to Rule of Mixtures, Kerner–Uemura–Takayanagi, Nicolai-Narkis and Béla-Pukánsky models. All of them will validate the experimental obtain values and they anticipate a good adhesion between both phases.
Nevertheless, for low levels of incorporation of PHA (up to 30%), where PLA is expectantly the matrix, the experimental data seems to deviate from the perfect adhesion models, suggesting a decrease on the adhesion between both polymeric phases.
The impact energy varies over 157% over the entire blend composition. It’s possible to identify that for blends with PHA weight fraction lower than 50% the impact strength of the blend is higher than the pure base polymers. The highest synergetic effect is found for the blend PHA/PLA of 30/70. The second maximum is found for the inverse composition.
PLA has a Heat Deflection Temperature substantially lower than PHA. For the blends, the HDT increases with the increment upon the % of incorporation of PHA. Up to 50% PHA (PLA as matrix), the HDT is practically constant and equal to PLA value. Over this point (PHA matrix), the HDT of the polymer blends increases linearly with % of addition of PHA."
In this work the mechanical and impact behavior of PHA/PLA blend matrix reinforced with cellulosic fibers is investigated. It was also study the Heat-Deflection Temperature. The composite mechanical properties can be optimized trough... more
In this work the mechanical and impact behavior of PHA/PLA blend matrix reinforced with cellulosic fibers is investigated. It was also study the Heat-Deflection Temperature.
The composite mechanical properties can be optimized trough the variation of the fiber content on the composite. It's possible to predict the tensile properties recurring to modified Halpin-Tsai equation and Rule-of-Mixtures Model. According with this model it's possible to validate the experimental obtain values and anticipate that the incorporation of 30% (weight fraction) of fibers will drive to composite with an irregular fiber distribution.
The composite constituent's wf was optimized to tailor the composite to replace the petrol-based polymers used into interior door trims (mainly ABS and PP).
The composite mechanical properties can be optimized trough the variation of the fiber content on the composite. It's possible to predict the tensile properties recurring to modified Halpin-Tsai equation and Rule-of-Mixtures Model. According with this model it's possible to validate the experimental obtain values and anticipate that the incorporation of 30% (weight fraction) of fibers will drive to composite with an irregular fiber distribution.
The composite constituent's wf was optimized to tailor the composite to replace the petrol-based polymers used into interior door trims (mainly ABS and PP).
After a general discussion regarding different approaches towards sustainability with composite systems, several examples will be presented and discussed with respect to the design criteria for a given application. In fact, from the... more
After a general discussion regarding different approaches towards sustainability with composite systems, several examples will be presented and discussed with respect to the design criteria for a given application. In fact, from the mechanical characterization of PHA and PLA blends to the use of cork as a core in sandwich construction will aim for a larger incorporation of composite systems from renewable resources in structural applications and mass production.
The best way to obtain cellulosic fibers is to use the pulp wastes from the paper plants. The pre-processing of the fibers is a very complex and chemically heavy set of operations. At the end a small part of the fibers will be rejected... more
The best way to obtain cellulosic fibers is to use the pulp wastes from the paper plants.
The pre-processing of the fibers is a very complex and chemically heavy set of operations. At the end a small part of the fibers will be rejected and removed from the production system. Actually these rejected fibers are being incinerated at the furnace that dries the raw-wood. This means that after a set of chemical treatments, that ends with a bleach, the fibers will be incinerated driving to a waste of money, once that all the effort applied to the treatment are not useful, and by other side, the incineration can release some non-healthy emissions.
Is possible to use these rejected fibers on composite applications where there mechanical properties can improve the matrix.
We will present the study of the incorporation of these rejected fibers into a biodegradable blended matrix to replace, in some applications, the petrol-based polymers used into the automotive interior trims.
The mechanical, and thermal properties will be assess and compared, with the properties of the petrol-polymers used normally in this type of applications.
At the end it will be presented a concrete application studied during this work.
The pre-processing of the fibers is a very complex and chemically heavy set of operations. At the end a small part of the fibers will be rejected and removed from the production system. Actually these rejected fibers are being incinerated at the furnace that dries the raw-wood. This means that after a set of chemical treatments, that ends with a bleach, the fibers will be incinerated driving to a waste of money, once that all the effort applied to the treatment are not useful, and by other side, the incineration can release some non-healthy emissions.
Is possible to use these rejected fibers on composite applications where there mechanical properties can improve the matrix.
We will present the study of the incorporation of these rejected fibers into a biodegradable blended matrix to replace, in some applications, the petrol-based polymers used into the automotive interior trims.
The mechanical, and thermal properties will be assess and compared, with the properties of the petrol-polymers used normally in this type of applications.
At the end it will be presented a concrete application studied during this work.