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Percorrer por autor "Pereira, António M."

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  • Development of an Additive Manufacturing System for the Deposition of Thermoplastics Impregnated with Carbon Fibers
    Publication . Reis Silva, Miguel; Pereira, António M.; Alves, Nuno; Mateus, Gonçalo; Mateus, Artur; Malça, C.
    This work presents an innovative system that allows the oriented deposition of continuous fibers or long fibers, pre-impregnated or not, in a thermoplastic matrix. This system is used in an integrated way with the filamentary fusion additive manufacturing technology and allows a localized and oriented reinforcement of polymer components for advanced engineering applications at a low cost. To demonstrate the capabilities of the developed system, composite components of thermoplastic matrix (polyamide) reinforced with pre-impregnated long carbon fiber (carbon + polyamide), 1 K and 3 K, were processed and their tensile and flexural strength evaluated. It was demonstrated that the tensile strength value depends on the density of carbon fibers present in the composite, and that with the passage of 2 to 4 layers of fibers, an increase in breaking strength was obtained of about 366% and 325% for the 3 K and 1 K yarns, respectively. The increase of the fiber yarn diameter leads to higher values of tensile strength of the composite. The obtained standard deviation reveals that the deposition process gives rise to components with anisotropic mechanical properties and the need to optimize the processing parameters, especially those that lead to an increase in adhesion between deposited layers.
    2019Artigo científico Acesso aberto Ver mais
  • Interlaminar fracture in woven carbon/epoxy laminates
    Publication . Reis, Paulo N. B. ; Ferreira, José A. M. ; Costa, José D. M. ; Pereira, António M.
    This paper describes an experimental study developed to characterize the mode I and mode II fracture toughness of carbon/epoxy woven composites, using DCB and ENF tests, respectively. The laminates were manufactured using an epoxy resin and twelve woven balanced bi-directional layers of carbon fibres, all of them with the same orientation (0/90º). Significant instantaneous delaminations were observed particularly for the DCB specimen, which were responsible for an oscillatory behaviour of GI versus crack length. The maximum values obtained for GIC and GIIC were 281 and 1800 J/m2, respectively.
    2014-09-09Artigo científico Acesso aberto Ver mais