1,720,975 research outputs found
Taking advantage of the hybrid effect in thin-ply pseudo-ductile laminates: 17th European Conference on Composite Materials, ECCM 2016
No full textHybrid laminates and angle-ply laminates with thin unidirectional carbon plies have been shown to give a pseudo-ductile response with more gradual failure than conventional composites. This paper shows the effect of ply thickness on tensile strength. Significant enhancements to the failure strain are demonstrated in glass-carbon hybrid composites, in hybrids with different grades of carbon fibre and in carbon fibre laminates combining 0° and angle plies. In addition to providing pseudo-ductility, these laminates therefore enable greater advantage to be taken of the intrinsic properties of the materials
Role of fibre fragmentation on pseudo-ductility of thin-ply [±27<sub>7</sub>/0]<sub>s</sub> carbon fibre laminates with high modulus 0° plies under compressive and flexural loading
No full textPseudo-ductile tensile, compressive and flexural behaviour was achieved in a thin-ply carbon fibre [±277/0]s laminate with different fibre types in the angle plies and 0° plies. The laminate with the present layup was tested in both tension and compression, the latter through an unconventional indirect compressive test method using a sandwich beam configuration and the compressive stress was derived by considering the change in position of the neutral axis. The tests demonstrated for the first time that pseudo-ductility and progressive failure can be obtained under compressive loading on thin-ply [±θm/0n]s laminates using a combination of intermediate modulus and high modulus fibre prepregs. Delamination was suppressed throughout the testing and only occurred at the final fracture of the angle plies. Multiple fibre fractures of the 0° plies were obtained within the laminate with the support of the surrounding angle plies in both loading cases. When the laminate was subjected to monolithic flexure, a gradual failure and significant amount of non-linearity occurred. This was primarily due to 0° ply fragmentation on both the compressive and tensile sides of the beam; the fragmentation on both sides resulted in shifts of the neutral axis, retarding the strain increase on the compressive side, delaying the final failure and achieving a higher failure strain in flexure than in compression
A pseudo ductile angle-ply sub-laminate approach for multidirectional thin ply CFRP laminates: 17th European Conference on Composite Materials, ECCM 2016
No full textAnalytical modelling of thin ply angle-ply [±θ/0]s carbon-epoxy layups consisting of intermediate modulus MR60 and ultra high modulus YSH70A prepreg materials has been conducted to establish a candidate configuration for use as a pseudo-ductile sub-laminate in a multidirectional laminate. These layups have demonstrated considerable pseudo-ductility via gradual failure of the 0° ply. Stress-strain predictions of [±25/0]s, in particular, have shown that this layup possesses a high initial modulus of 135 GPa and produce a pseudo-ductile strain of 1.43%, for a strength of 761 MPa. Selected as a sub-laminate configuration, this layup has been applied to two stacking sequences: [30/0/ - 30]s and [45/0/ - 45]s, where the global orientations correspond to the direction of the 0° ply in each sub-laminate. Classical laminate analysis indicates that these multidirectional laminates can exploit the pseudo-ductility of the sub-laminates to achieve a gradual failure at a higher scale
Reduced notch sensitivity in pseudo-ductile CFRP thin ply angle-ply laminates with central 0° plies
No full textThis paper presents an experimental investigation on the unnotched and open-hole tensile behaviour of pseudo-ductile thin ply angle-ply carbon fibre/epoxy laminates with central 0° plies. Laminates with two different configurations of [±265/0]s and [±252/0]s were designed and tested under unnotched and open-hole tensile loading. Metal-like tensile stress-strain curves with a plateau were observed in both unnotched configurations. The open-hole net-section strength of the [±252/0]s laminate attained 96% of the unnotched “yield” strength. Digital image correlation and X-ray CT-scan images showed that the same damage mechanisms of central 0° ply fragmentation and local dispersed delamination observed in unnotched pseudo-ductile laminates were present in the open-hole specimens of the same configuration. These damage mechanisms caused stress redistribution around the hole and reduced the notch sensitivity in pseudo-ductile laminates under open-hole tensile loading. The main factors governing the open-hole performance are also discussed
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
Energy dissipation during delamination in composite materials – An experimental assessment of the cohesive law and the stress-strain field ahead of a crack tip
Get PDFThis paper presents detailed experimental information on mode-II delamination development in fibre/epoxy composite materials and provides observations about the process zone in the vicinity of the crack tip. It is shown that the energy dissipated in delamination propagation is spent on two ways (i) creating new fracture surfaces (delamination) and (ii) nonlinear shear deformation in the composite plies adjacent to the delaminating interface. Therefore, the nonlinear process zone is not restricted to the resin-rich interface between the layers, but also extends into the fibre/epoxy composite layers. This is different from the conventional assumption in modelling delamination using cohesive elements where the fibre/epoxy layers are fully linear-elastic and the process zone is lumped at the plane of fracture. Based on the accurately measured displacement field around the crack tip, the experimental traction-separation relation at the interface is found to be trapezoidal which is again different from the conventional bilinear cohesive law.</p
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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