1,721,143 research outputs found
Aligned short fibre hybrid composites with virgin and recycled carbon fibres
Get PDFOne of the main problems in industrial applications of carbon composite materials is recycling end of life products. Usually chopped recycled fibres are randomly dispersed in materials as low-grade additives for non-structural applications; however, in order to maximize economic and functional viability, these fibres should be reused as reinforcement for high performance structural composites. The fibre alignment level is the key factor to increase the fibre volume fraction, and consequently the performance of recycled composites. Another important factor is the impact of the fibre recovery process on the mechanical properties of carbon fibres. Carbon fibres can be damaged during the fibre recovery process leading to a significant loss of strength, but the modulus is almost the same as that of virgin carbon fibres. The aim of this research is to manufacture intermingled hybrid composites using highly aligned new and recycled discontinuous carbon fibres with the HiPerDiF (High Performance Discontinuous Fibres) method to increase the availability of recycled carbon fibres. This method enables manufacturing of discontinuous fibre hybrid composites with different fibre mixing ratios; the constituents are intimately mixed and the hybridisation is achieved within the ply. In this work, the stiffness and the failure properties of aligned short fibre composites, as a function of the recycled to virgin carbon fibres ratio, are investigated. The HiPerDiF method proved to be a valuable remanufacturing method to achieve high performance short fibre composite from end of life recycled composites
Spring-in angle as molding distortion for thermoplastic matrix composite
Get PDFIn this work, the spring-in angle behavior of a U-channel shaped thermoplastic matrix laminate is studied.
The consolidation of the U-channel shaped profile having two different corner radii took place in an
autoclave. Spring-in angle was measured at room temperature, after cooling in the autoclave, and during
subsequent heating at different temperatures and after final cooling to room temperature. Different thermally
induced spring-in angle behaviors were observed for the two inner radii of U-specimen. Thermal
expansion coefficients in the through the thickness and in-plane directions were measured. Experimental
spring-in angle data were then compared with a differential model derived from the Radford model.
Some differences between the model results and experimental spring-in data were observed. The differences
observed between the two radii and between experimental and model results were attributed to
the existence of fibers distortion at the corner, leading to significant fibers misalignment and wrinkling.
Consequently, the Radford model was modified to account for the increase of thermal expansion coefficient
in the through the thickness direction. Results showed a better agreement with experimental data.
Finally, the difference observed in the spring-in angle before and after heating of the composite indicates
the relevance of non-thermoelastic effects in thermoplastic matrix composites
The High Performance Discontinuous Fibre (HiPerDiF) Method for the Remanufacturing of Mixed Length Rreclaimed Carbon Fibres
Get PDFThe wide spread of carbon fibres reinforced polymers in various engineering and industrial sectors over the last decades poses the challenge of dealing with production waste and end-of life products. In the case of the thermosetting-based composites, recycling is a two-step process: a reclamation stage, where the fibres are retrieved by degrading the matrix, and a remanufacturing stage to produce a reusable material. Typically, reclamation processes deliver fibres that are fragmented in short length, moreover, these often present a distribution of length and physical or mechanical properties. The HiPerDiF technology allows to deliver commercially valuable and high performance recycled composite materials by remanufacturing the reclaimed fibres into highly aligned discontinuous fibre composites. This paper demonstrates the possibility of simultaneously remanufacture fibres with different lengths. The mechanical properties of the obtained material are characterised with a novel tensile test methodology based on interlaminated hybrid specimens.<br/
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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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