1,721,003 research outputs found
Impact damage detection in composite plates using deflectometry and the Virtual Fields Method
No full textThis paper presents a new method for detecting damage in layered composite materials using a simple measurement technique, deflectometry. The aim is to locate the damage in a specimen and provide a “signature” from the measured surface slopes. Firstly, this method is applied to plate specimens using numerical and experimental data. Secondly, damage indicator based on a new application of the virtual fields method to compute local apparent gaps in equilibrium is presented and used to process the measurements on plates. It is shown that the damage indicator is very sensitive, allowing detection of damage that is difficult to identify directly from the strain maps
Combining fibre rotation and fragmentation to achieve pseudo-ductile CFRP laminates
Get PDFThe pseudo-ductility shown by thin ply angle-ply laminates has been coupled with the gradual fragmentation of unidirectional (0°0°) plies to yield a metal-like stress–strain curve for a [±θm/0n]s[±θm/0n]s laminate. This has led to a significant increase in pseudo-ductility than either angle-ply fibre rotation or 0°0° fragmentation have shown previously. Analytical modelling has been developed that accounts for the damage processes that contribute to the gradual failure of the 0°0° plies and predictions have been made taking into account the fragmentation, delamination and eventual failure of the laminate. Experimental results are shown to correlate well with the modelling, despite some variability in the responses. Analysis via X-ray computed tomography of tested specimens shows the progression of the fragmentation and delamination damage modes prior to laminate failure and provides an in-depth understanding of the process that leads to the demonstrated pseudo-ductile strains
An investigation into fatigue behaviour and damage progression in pseudo-ductile thin-ply angle-ply laminates
No full textThis paper presents a detailed investigation on the fatigue response and damage progression in pseudoductile thin-ply angle-ply laminates with two configurations: an intermediate modulus-high modulus fibre combined IM-HM [±277/0]s and a standard modulus SM-SM [±266/0]s laminate. 80% of the “yield” stress was found to be the maximum stress for both laminates, where they can withstand 106 cycles without obvious damage or stiffness reduction. When laminates containing pre-fractured 0° plies were loaded in fatigue, both of the laminates showed a delamination dominated damage mode: the delamination initiated from the pre-fractured 0° plies and propagated at the interface between the 0° and angle plies with increasing number of cycles. An estimated delamination growth rate based on the stiffness reduction and delamination initiated from 0° ply fracture are also discussed. The IM-HM laminate with broken 0° fibres can still withstand fatigue loading at 80% severity without further modulus reduction or damage progression, whilst the SM-SM failed in delamination within a small number of cycles
Identification of the local stiffness reduction of a damaged composite plate using the virtual fields method
No full textIn the present study, a damage detection problem is formulated as the identification of the spatial stiffness distribution in a damaged composite plate. Full-field heterogeneous curvature fields obtained from an optical deflectometry technique are processed by using the virtual fields method adapted to retrieve the 2D stiffness distribution map of a damaged carbon-epoxy plate. The method not only picks up the location of the damage but also provides a fairly good estimate of the stiffness reduction in the damaged area. In this paper, the procedure is described, validated on simulated measurements and some initial experimental results are given. (c) 2007 Elsevier Ltd. All rights reserved.</p
A procedure for producing reflective coatings on plates to be used for full-field slope measurements by a deflectometry technique
No full textRetained strength of UHTCMCs after oxidation at 2278 K
Get PDFIn the frame of Horizon 2020 European C3HARME research project, the manufacture of ZrB2-based CMCs was developed through different processes: slurry infiltration and sintering, radio frequency chemical vapour infiltration (RF-CVI) and reactive metal infiltration (RMI). To assess the high temperature stability, room temperature bending strength was measured after oxidizing the samples at 2278 K and compared to the strength of the as-produced materials. Microstructures were analysed before and after the thermal treatment to assess the damage induced by the high temperature oxidation. Short fibre-reinforced composites showed the highest retained strength (>80%) and an unchanged stress-strain curve
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
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