1,721,006 research outputs found
Damage mechanisms in the CAI failure of thin z-pinned composite laminates
Full text linkThe results of an experimental investigation into the compression after impact (CAI) performance of thin z-pinned carbon-epoxy laminates are reported in this paper. Unpinned and z-pinned [02/902]S and [0/±45/90]S samples were impacted at energies varying between 2 J and 35 J and then subjected to compression loading until failure. The amount and nature of the damage induced by impact and the damage mechanisms leading to CAI failure were characterized by X-radiography and through visual observation of the sample surfaces. The study shows that the effect of z-pins may be beneficial or detrimental to the post-impact strength of the laminates depending on the energy of the impact. The sequence of the main damage mechanisms observed on the laminates during the compression tests is illustrated and discussed to clarify the role of z-pins in controlling the residual strength of the impacted laminates over the full range of examined impact energies
Damage mechanisms in thin stitched laminates subjected to low-velocity impact
No full textThis study examines the influence of stitching on the structural and damage response of thin carbon/epoxy [02/902]s laminates subjected to low-velocity impact. Impact tests were carried out on unstitched and stitched laminates and the nature and extent of damage at various impact energies was characterized by radiographic analyses. The main results of the study are illustrated and discussed to highlight the role and the potential of stitches for improving the impact damage resistance of this class of laminated composites
Impact and post-impact behavior of composite laminates reinforced by Z-Pins
No full textDelamination, i.e. the separation between layers that occurs by failure of the resin-rich interlaminar interface, is a direct consequence of the lack of out-of-plane reinforcements and, undoubtedly, the most common damage mode in laminated composites. Delaminations induced by low-velocity impacts are of primary concern in structural applications, since impact damage, often miss-detected, may propagate, impairing the load bearing capacity of the component, particularly under compressive loads. Preventing delamination, as well as delaying and limiting its propagation, are thus key issues in the design of composite structures. Over the last decades, many strategies have been proposed to address this problem. Among them, the introduction of through-thickness reinforcements (stitching, pinning and stapling) has proven to be effective in improving the interlaminar properties of composite materials. In particular, recent studies have shown that Z-pinning, which consists in inserting high stiffness pins through the thickness of uncured laminates, may significantly enhance the delamination resistance of laminated components. In this study, conventional and Z-pin reinforced [02/902]s graphite/epoxy laminates were subjected to low-velocity impact and compression after impact (CAI) tests in order to examine the effect of the reinforcements on the impact response and the residual post-impact properties of the laminate. The results show that Z-pinning significantly reduces the extent of delamination induced by impact, while, on the contrary, it appears to only marginally improve the post-impact compressive strength of the laminates
Effect of thermal treatments on an ordered Fe-37 at% Al intermetallic compound with Ce, La and Zr additions
No full textThe microstructure of an ordered Fe-37 at% Al intermetallic compound with Ce, La and Zr additions has been investigated after annealing in the temperature range 1023-1533 K. The order-disorder critical temperature determined by X-ray diffractometry was found to be approximate to 1540 K. Second phases containing Ce, La and Zr have been identified as Al(8)XFe(4), Al(4)X (X=Ce, La) and Al6Fe6Zr. Size, morphology and distribution of these phases after different thermal treatments have been described by means of SEM observations with EDS microanalysis
Effect of stitching on the flexure after impact behavior of thin laminated composites
No full textThe paper investigates the effect of stitching on the post-impact flexural performance of two classes of thin carbon/epoxy laminates. Unstitched and stitched laminated samples were first impacted with energies ranging between 1 J and 8 J by an instrumented drop-weight testing machine. The residual flexural properties of impacted samples were then assessed by three-point bending tests. The damage induced by impact and by post-impact bending was characterized in detail by visual inspection and penetrant-enhanced X-radiography. The results of the experimental analyses are illustrated and discussed to highlight the correlation between the residual flexural properties and the key fracture modes occurring in the laminates. The study shows that even though stitching is capable of improving the delamination resistance of the laminates, it may also drastically reduce their flexural strength. It is also seen that the residual post-impact flexural properties, which are controlled by the peculiar impact damage mechanisms of stitched and unstitched laminates, may be greatly degraded by impacts with energy above a critical threshold value
Punching shear strength of reinforced recycled concrete slabs
No full textThis paper reports on the experimental punching shear behaviour of simply supported structural slabs realized by reinforced Recycled aggregates Concrete (RC) made with coarse recycled aggregates by demolished concrete only (CRcA). This investigation was made with the aim to provide a best understanding of RC slabs structural behavior. The experimental campaign has been carried out on 12 reinforced RC slabs. Three reinforced Natural aggregate Concrete (NC) slabs have been casted and tested as control specimens. Four CRcA replacement percentages (30, 50, 80 and 100%) have been considered. The tests on the punching shear behavior of simply supported reinforced RC slabs have been analyzed. The results show that the punching shear strength of RC and NC slabs are very similar
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
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
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