Achieving class a appearance on fiber-reinforced substrates / Donald H. Campbell in COATINGS TECH, Vol. 18, N° 6 (06/2021)  

[article]  inCOATINGS TECH > Vol. 18, N° 6 (06/2021) . - p. 32-40 Titre : Achieving class a appearance on fiber-reinforced substrates : Achieving Class A appearance over fiber-reinforced substrates can be challenging. Learn about solutions and the evolving measurements used to characterize topcoated surface appearance Type de document : texte imprimé Auteurs : Donald H. Campbell, Auteur ; G. Singh, Auteur ; Cindy Peters, Auteur ; Jacob Dumbleton, Auteur Année de publication : 2021 Article en page(s) : p. 32-40 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Automobiles -- Revêtements:Automobiles -- Peinture Composites à fibres de carbone Eléments finis, Méthode des 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. Revêtements -- Finition:Peinture -- Finition Surfaces (Physique) Surfaces courbes Topographie Index. décimale : 667.9 Revêtements et enduits Résumé : Achieving Class A appearance over fiber-reinforced substrates can be challenging. We discuss the evolving measurements used to characterize topcoated surface appearance. The influence of carbon fiber on the surface appearance of a thermoplastic resin-transfer-molding (RTM) substrate is related to differences in thermal expansion within the substrate. The mechanism identified here is then extended to several chopped-fiber-filled thermoplastic substrates where the fiber-mapping effect is manifested in a different manner. We then investigate the influence of thick-film applications to the Class A surface on appearance. Our analysis finds that both the depth and the width or wavelength of the substrate affect the ability of the thick films to cover fiber mapping. Note de contenu : - Class a appearance defined and measured - Mechanism of fiber influence on appearance - Potential solutions - Ongoing projects in this area - Fig. 1 : Constituent Wave Packets from BYK-Gardner Wavescan - Fig. 2 : Cross section of RTM substrate - Fig. 3 : Topography of topcoated RTM substrate at 25°C adn 90°C - Fig. 4 : Topography of uncoated RTM substrate at 25°C and 90°C - Fig. 5 : RTM plaque : resin-only area CTE - Fig. 6 : Effect of fiber on topcoated appearance at bake and room temperatures - Fig. 7a and 7b : Effect of fiber on substrate surface at bake and room temperatures - Fig. 8 : Wavescan values for varied primer thicknesses - Fig. 10 : Relationship of primer thickness to defect wavelength ratio to defect coverage - Fig. 11 : Finite Element Analysis of defect propagation through primer - Fig. 12a and 12b : Appearance values for topcoat processes on carbon-fiber-filled polyamide and propylene - Table 1 : Changes of topography with temperature - Table 2 : Finite Element Analysis of varied primer thickness, wavelength, and poisson's ratio En ligne : https://drive.google.com/file/d/16c5zuNUS2yU5gQUhSR_1URCxd_BXHbzq/view?usp=share [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=35988 [article]

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Novel embossing system for replicating micro-structures on curved surfaces / S. C. Nian in INTERNATIONAL POLYMER PROCESSING, Vol. XXIX, N° 3 (07/2014)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXIX, N° 3 (07/2014) . - p. 364-370 Titre : Novel embossing system for replicating micro-structures on curved surfaces Type de document : texte imprimé Auteurs : S. C. Nian, Auteur Année de publication : 2014 Article en page(s) : p. 364-370 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Films plastiques Gaufrage à chaud Microstructures Polycarbonates Résines photosensibles Surfaces (technologie) Surfaces courbes Index. décimale : 668.4 Plastiques, vinyles Résumé : Hot embossing is widely used to replicate micro-structures on polymer plate surfaces. The polymer parts of curved surfaces with micro-structures have important functions in various optoelectronic components. However, due to the high precision needed for embossing machines and mold manufacturing, achieving uniform pressure on curved surfaces during the embossing process is difficult. This study modified conventional hot embossing processes to develop an elastic bag embossing system (EBES) for replicating micro-structures on curved surfaces. The pressure equalizing properties of the elastic bag enabled uniform application of pressure on curved surfaces embossed with a general hot compression machine. For the EBES-assisted hot embossing process, a nickel stamper was attached to the elastic bag to compress and replicate micro-structures on the PC film covering the mold surface with single direction curve. This study also developed an EBES-assisted UV exposure process that used a PDMS soft-mold attached to the elastic bag surface to compress the UV curable photoresist covering the surface of the convex lens. Micro-structures were then formed by exposing the photoresist. Experimental results showed that the EBES with Ni stamper could successfully replicated micro-structures onto a 200 mm × 200 mm curved PC film and that the EBES-assisted UV exposure could successfully produced a 50 mm diameter fresnel lens on a convex profile with material of UV photoresist. Experimental tests of pressure-sensitive film showed that EBES enables uniform application of pressure on curved surfaces during the embossing process on standard hot compression machines. The experimental results confirm that the EBES developed in this study is an efficient and economical method for replicating micro-structures on curved surface. Note de contenu : - EXPERIMENT : Setup for EBES-assisted hot embossing process - Setup for EBES-assisted UV exposure - RESULTS AND DISCUSSION : Embossing pressure distribution - Experimental results for EBES-assisted hot embossing process - Experimental results for EBES-assisted UV exposure DOI : 10.3139/217.2790 En ligne : https://drive.google.com/file/d/1FpVYjGOVkNZ_1q_-HRDMGrNnssmXTKyl/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=21734 [article]

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