1,720,972 research outputs found
Electrospun nanofibers as reinforcement for composite laminates materials – a review
Full text linkIn the last few decades nanofibers have been developed and introduced in a vast number of industrial and research applications. One of their most effective use is as interleaved reinforcement for composite laminate materials against delamination. Nanofibrous mats have the ideal morphology to be embedded between two plies of a laminate, and a vast and deep research has been carried out investigating their effect on the global behaviour of a composite laminate. This review is the first of its kind to date which presents a detailed state-of-the-art on the effect of nanofibrous interleaves into composite laminates with focus on the mechanical performances and behaviours of nanomodified materials. A detailed description of the working mechanisms of the nanointerleave under different load cases is presented, and a comparative analysis between papers in literature will provide readers with a powerful tool to understand and use nanofibers for reinforcing purposes
Influence of electrospun Nylon6,6 nanofibrous mats to the interlaminar strength of Carbon Fiber-Epoxy composite laminates: experimental and numerical analyses
No full textThe effect of Nylon 6,6 electrospun nanofibers interleaved in composite laminate material is numerically simulated to investigate the damage evolution a nanomodified laminate interface. DCB and ENF mechanical test results from a previous work of the authors are used as benchmark for numerical simulations: carbon fiber/epoxy matrix 0/90 prepreg laminate are simulated and mechanical properties are determined for both virgin and nanomodified configurations. Numerical simulation with finite element software Abaqus using implicit time integration were performed to build a numerical model to simulate both the tests taking into account the presence on nanofibers. Nanofibrous interlayer was simulated using a bilinear damage law corresponding to resin a nanofibrous materials behavior. Virgin and nanomodified configuration for experimental and numerical results are compared and it is shown that numerical results are in good agreement with experimental one
Delamination localisation and length estimation in composite laminate beam by VSHM and pattern recognition methods
Full text linkThe focus of this work is to investigate the delamination damage in laminate composite beams, to fix a Vibration-based structural health monitoring (VSHM) method for the laminate structures. The analysis is concentrated on the vibration characteristics of the samples and, in particular, the attention is addressed on the first several natural frequencies of a composite laminate beam with a delamination damage. The core of this work is an experimental investigation on the vibration response of a composite laminate beam and its changes caused by delaminations with different sizes and in different locations of the beam. The study is divided in 3 sections: delamination detection, delamination localization, and delamination estimate. The aim is to determine how the first six harmonics frequencies change due to the delamination, and the results show that they can be successfully used to investigate the presence, the location and the dimensions of the delamination in a composite beam. A Pattern Recognition analysis is used to locate the damage, while the detection and the evaluation are done using the changes in the harmonic frequencies. A finite element analysis is performed, and the variations of the natural frequencies due to delamination are in good agreement with the experimental results
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
Numerical Assessment of Impact Behavior of Composite Laminates with Variable Interply Delamination Strength
No full textAbstractThe reasons of increasing use of composite laminates in modern aircrafts, vehicles and other applications are related to their high specific strength and modulus, together with their flexibility in design. Delamination is one of most common failure mechanisms for composite materials. By interleaving a nanofibrous mat between laminate plies it can be possible to control the interlaminar delamination strength. The nanofibrous mat at a laminate interface is impregnated by the resin during the curing process. In previous works, the authors tested delamination toughness and identified the cohesive zone properties of nanomats with varying fibre diameter, fiber arrangement (random, aligned) and mat thickness. The results showed that, by varying those parameters, a toughening or an embrittlement of the interface can be obtained. The modification induced by the nanomat can be therefore exploited in order to tailor the interply delamination strength of the laminate. The aim of this work is simulate the impact strength of a composite laminate giving different strength to interplies in order to proof that it is possible to increase the impact energy absorbed by the composite, in the perspective of optimization for use in impact attenuation
A numerical investigation on the interlaminar strength of nanomodified composite interfaces
No full textThe effect of Nylon 6,6 electrospun nanofibers interleaved in composite laminate material is simulated numerically to investigate the differences in the fracture strength between a nanomodified laminate interface and the corresponding non-modified material. DCB and ENF mechanical test results from a previous work of some of the authors are used as reference for the identification of cohesive zone model by numerical simulations with the finite element software Abaqus using implicit time integration. A bilinear damage law came out to be necessary to match the experimental behavior of the nanomodified interface, while the virgin material can be represented through a simple linear damage law. The necessity of using a bilinear damage law has been related to the crack bridging and to the obstacle to crack growth caused by nanofibers
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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