1,721,194 research outputs found
A closed-loop recycling process for discontinuous carbon fibre polyamide 6 composites
No full textThe effects of a closed-loop recycling methodology are evaluated for degradation using a discontinuous carbon fibre polyamide 6 (CFPA6) composite material. The process comprises two fundamental steps: reclamation and remanufacture. The material properties are analysed over two recycling loops, and CFPA6 specimens show a total decrease of 39.7% (±3.5) in tensile stiffness and 40.4% (±6.1) in tensile strength. The results of polymer characterisation and fibre analysis suggested that the stiffness reduction was likely due to fibre misalignments primarily caused by fibre agglomerations, as a result of incomplete fibre separation, and by fibre breakages from high compaction pressures. The ultimate tensile strain was statistically invariable as a function of recycling loop which indicated minimal variation in polymer structure as a function of recycling loop. To the authors’ best knowledge, the mechanical performance of the virgin CFPA6 is the highest observed for any aligned discontinuous carbon fibre thermoplastic composites in the literature. This is also true for recycled specimens, which are the highest observed for any recycled thermoplastic composite, and, for any recycled discontinuous carbon fibre composite with either thermosetting or thermoplastic matrices
Development of a closed-loop recycling process for highly aligned discontinuous carbon fibre thermoplastic composites
No full textIn this study the effects of a closed-loop recycling methodology are evaluated for degradation using thermoplastic ocmposites based on discontinuous fibres. The process comprises two fundamental steps: reclamation and remanufacture. The material properties are analysed over two recycling loops. Carbon fibre reinforced polypropylene (CFPP) specimens show no decrease in mechanical properties over repeated recycling loops, the final specimens show an increase of 26 % and 43 % in ultimate tensile strength and ultimate strain, respectively. These are attributed to cumulative matrix residue on the fibre surface after reclamation and subsequently increased fibre-matrix adhesion. The improvement of CFPP properties validate the potential of this proof-of-concept, closed-loop recyclable material. Future studies will investigate alternative, higher performance matrices
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
An evaluation of life cycle assessment and its application to the closed-loop recycling of carbon fibre reinforced polymers
Full text linkLife cycle assessment (LCA) is a valuable tool for establishing the environmental burdens of a composite material over its lifetime. It is therefore of importance to the composites industry as a material selection tool when determining the applicability of recycled composites in the component design phase. This review paper evaluates the LCA framework and its ability to accurately determine the benefits of closed-loop composite recycling, with the aim of aiding future material selection for recycled CFRP. LCA is a powerful tool for CFRP assessment when used in combination with an economic and technical component as covered by the integrated Life Cycle Engineering approach. The broad range of values available in LCA databases may prove an issue for cross comparison between studies and provide disparate results leading to impractical conclusions. The use phase offers the greatest potential for CFRP emissions savings in the transport sector; the advent of closed-loop recycling for CFRP may provide the multiple use phases required to breakeven on the significant energy burden of production or possibly provide net environmental savings gains over traditional materials
Development of a closed-loop recycling process for discontinuous carbon fibre polypropylene composites
No full textIn this study the effects of a closed-loop recycling methodology are evaluated for degradation using a discontinuous carbon fibre polypropylene (CFPP) composite material. The process comprises two fundamental steps, reclamation and remanufacture. The material properties are analysed over two recycling loops. For neat polypropylene, the molecular weight analysis indicates evidence of minimal matrix degradation that does not affect the material behaviour, as demonstrated by the shear tests. CFPP specimens show no decrease in mechanical properties over repeated loops, the final specimens show an increase of 26% and 43% in ultimate tensile strength and ultimate strain, respectively. These are attributed to cumulative matrix residue on the fibre surface after reclamation and subsequently increased fibre-matrix adhesion. The improvement of CFPP properties and insignificant variability in the tensile properties and molecular weight distribution of neat polypropylene validate the potential of this proof-of-concept, closed-loop recyclable material. Future studies will investigate alternative, higher performance matrices
Devleopment of a closed-loop recycling process for short carbon fibre composites: Matrix
No full textIn this study, the degradation effects of multiple closed-loop recycling processes evaluated for polypropylene. This is the first in a series of studies that aim to develop a fully recyclable composite material based on aligned discontinuous carbon fibre. Mechanical and material property fluctuations are analysed after three iterations. Molecular weight analysis indicates slight degradation in chain length; however, this is not reflected in material or mechanical performance. The limited variability of the tensile properties and the molecular weight distribution after multiple recycling iterations is insignificant and therefore promising for further development of the recyclable composite material by introducing fibres
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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