Enhanced infrared heating of thermoplastic composite sheets for thermoforming processes / M. Längauer in INTERNATIONAL POLYMER PROCESSING, Vol. 36, N° 1 (2021)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. 36, N° 1 (2021) . - p. 35-43 Titre : Enhanced infrared heating of thermoplastic composite sheets for thermoforming processes Type de document : texte imprimé Auteurs : M. Längauer, Auteur ; G. Zitzenbacher, Auteur ; C. Burgstaller, Auteur ; C. Hochenauer, Auteur Année de publication : 2021 Article en page(s) : p. 35-43 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Chauffage Composites à fibres -- Thermoformage Composites à fibres de carbone Composites à fibres de verre Polyamide 6 Polyamide 66 Rayonnement infrarouge Index. décimale : 668.4 Plastiques, vinyles Résumé : Thermoforming of thermoplastic composites attracts increasing attention in the community due to the mechanical performance of these materials and their recyclability. Yet there are still difficulties concerning the uniformity of the heating and overheating of parts prior to forming. The need for higher energy efficiencies opens new opportunities for research in this field. This is why this study presents a novel experimental method to classify the efficiency of infrared heaters in combination with different thermoplastic composite materials. In order to evaluate this, different organic sheets are heated in a laboratory scale heating station until a steady state condition is reached. This station mimics the heating stage of an industrial composite thermoforming device and allows sheets to slide on top of the pre-heated radiator at a known distance. By applying thermodynamic balances, the efficiency of chosen parameters and setups is tested. The tests show that long heating times are required and the efficiency of the heating is low. Furthermore, the efficiency is strongly dependent on the distance of the heater to the sheet, the heater temperature and also the number of heating elements. Yet, using a full reflector system proves to have a huge effect and the heating time can be decreased by almost 50%. Note de contenu : - Specific heat capacity - Heating tests without reflectors - Heating tests using reflectors - Table 1 : Input parameters for the calculation of the enthalpy and heat flux (a derived from material data sheet) DOI : https://doi.org/10.1515/ipp-2020-3923 En ligne : https://drive.google.com/file/d/1NRCKw4IGMW7OJRvSI5wngwS8omSB2xAy/view?usp=shari [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=36344 [article]

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Experimental and numerical investigation of shrinkage and warpage of a U-shaped injection molded part / Stefan Kleindel in INTERNATIONAL POLYMER PROCESSING, Vol. XXXI, N° 1 (03/2016)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXXI, N° 1 (03/2016) . - p. 68-81 Titre : Experimental and numerical investigation of shrinkage and warpage of a U-shaped injection molded part Type de document : texte imprimé Auteurs : Stefan Kleindel, Auteur ; R. Eder, Auteur ; H. Schretter, Auteur ; C. Hochenauer, Auteur Année de publication : 2016 Article en page(s) : p. 68-81 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Composites à fibres de verre Composites à fibres de verre -- Moulage par injection Gauchissement (matériaux) Mesure Polyamides Un polyamide est un polymère contenant des fonctions amides -C(=O)-NH- résultant d'une réaction de polycondensation entre les fonctions acide carboxylique et amine. Selon la composition de leur chaîne squelettique, les polyamides sont classés en aliphatiques, semi-aromatiques et aromatiques. Selon le type d'unités répétitives, les polyamides peuvent être des homopolymères ou des copolymères. Polyoxyméthylène Retrait au moulage Simulation par ordinateur Index. décimale : 668.4 Plastiques, vinyles Résumé : Prediction of shrinkage and warpage of injection molded plastic parts is a key issue of injection molding simulation. In the present work a U-shaped part is investigated experimentally and by means of state of the art injection molding simulation software. The part has thick walls in the corner where inner defects such as voids and porous zones may appear. Experiments and simulations were performed with POM and glass fiber reinforced polyamide. Measurements of pressure in the cavities and temperature profiles around the cavities were used to validate the numerical model. In case of POM it was found that warpage predictions are way off when the void volume is high and in good agreement when the void volume is minimized. No such correlation was observed in case of fiber reinforced materials. Here, shrinkage and warpage are dominated by the fiber orientation state with minor influence of the processing conditions. Predicted warpage was found to be extremely dependent on the used closure approximation. Note de contenu : - PROBLEM DESCRIPTION - EXPERIMENTAL : Mold design - Measurements - NUMERICAL : Computational mesh - Material data - Boundary conditions - RESULTS : Experimental results - Simulation results - Discussion DOI : 10.3139/217.3148 En ligne : https://drive.google.com/file/d/1Lw0SrrPweDXNzbZ_k8OjnAguT44jH1tU/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=25770 [article]

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Measurement and numerical simulation of void and warpage in glass fiber reinforced molded chunky parts / Stefan Kleindel in INTERNATIONAL POLYMER PROCESSING, Vol. XXX, N° 1 (03/2015)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXX, N° 1 (03/2015) . - p. 100-112 Titre : Measurement and numerical simulation of void and warpage in glass fiber reinforced molded chunky parts Type de document : texte imprimé Auteurs : Stefan Kleindel, Auteur ; D. Salaberger, Auteur ; R. Eder, Auteur ; H. Schretter, Auteur ; C. Hochenauer, Auteur Année de publication : 2015 Article en page(s) : p. 100-112 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Composites à fibres de verre -- Moulage par injection Déformations (mécanique) Gauchissement (matériaux) Moulage par injection -- Défauts Polyamide 6 Simulation par ordinateur Index. décimale : 668.9 Polymères Résumé : The aim of this paper is to determine the reason for the large warpage of an injection molded chunky part made of glass fiber reinforced polyamide 6. State of the art commercial 3D injection molding simulation software was used to predict the warpage of the part. While the simulation predicted a product virtually free of warpage the molded parts showed a large deformation. Several molding experiments and X-ray computed tomography (?CT) scans of the moldings have been performed to figure out the reason for this. The ?CT scans revealed voids in the thick walls of the part. It was found that these defects were the main cause of the unreliable simulation results. Therefore it is concluded that voids can have a major influence on the reliability of numerical warpage predictions. This paper shows a simplified method to determine the zones were voids will appear and shows the comparison with ?CT-data. Note de contenu : - PROBLEM DESCRIPTION - MEASUREMENTS - EXPERIMENTS : Initial case - Variant - NUMERICAL ANALYSIS : Computational mesh - Material data - Fiber orientation - Warpage prediction - Process settings - Solver settings - RESULTS AND DISCUSSION : Experimental results - µCT results - Simulation results - Prediction of porous zones DOI : 10.3139/217.2984 En ligne : https://drive.google.com/file/d/1d_Zb9TKitwRi7zAjPmz5RFAXco_AJv4m/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=23427 [article]

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Prediction and validation of short fiber orientation in a complex injection molded part with Chunky geometry / Stefan Kleindel in INTERNATIONAL POLYMER PROCESSING, Vol. XXX, N° 3 (07/2015)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXX, N° 3 (07/2015) . - p. 366-380 Titre : Prediction and validation of short fiber orientation in a complex injection molded part with Chunky geometry Type de document : texte imprimé Auteurs : Stefan Kleindel, Auteur ; D. Salaberger, Auteur ; R. Eder, Auteur ; H. Schretter, Auteur ; C. Hochenauer, Auteur Année de publication : 2015 Article en page(s) : p. 366-380 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Composites à fibres -- Moulage par injection Composites à fibres courtes Distribution et orientation des fibres Prévision, Théorie de la Rhéologie Index. décimale : 668.4 Plastiques, vinyles Résumé : The paper shows the capability of state-of-the-art models and software to predict the fiber orientation distribution (FOD) on injection molded parts with a complex and thick-walled geometry. Predictions by the standard Folgar-Tucker model and the Reduced Strain Closure model were compared to measurements of the fiber orientation distribution obtained by X-ray Computed Tomography. Measurements and simulations were performed under different processing conditions to investigate the influence of injection velocity and packing pressure on the FOD. It was found that the predicted fiber orientation is in good qualitative agreement with the measurements. The measured orientation shows a distinct shell-core structure with high alignment of the fibers in flow direction in the shell layer and a orientation perpendicular to the flow direction in the core layer. While the orientation in the shell layer is predicted fairly well, a significant deviation is found in the prediction of the orientation in the core layer. Note de contenu : - MEASUREMENTS - EXPERIMENTAL - NUMERICAL : Computational mesh - Material data - Fiber orientation - Solver settings - RESULTS : Influence of the processing conditions on the fiber orientation - Results of the fiber orientation prediction - DISCUSSION : The mesh - Solver settings - Boundary condition for the fiber orientation - Rheological model - Suggestions for further investigations DOI : 10.3139/217.3047 En ligne : https://drive.google.com/file/d/1N1uretG0XwJdlIfK-nUmpBC-VUCobfhP/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=24332 [article]

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