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Ballistic Limit of CFRP Plates
Get PDFJAXA has carried out the hypervelocity impact tests of carbon fiber reinforced plastic (CFRP) plates together with University of Padova. Quasi-isotropic CFRP plates of 2.3, 3.5, and 4.7 mm in
thickness were tested. Aluminum sphere of 0.8 to 2.9 mm in diameter was used as projectiles. With a two-stage light gas gun, the projectile was launched with a velocity range of 2 to 5 km/sec in the normal direction to the CFRP plate. Since the perforated hole and the crater on the CFRP plate
after the impact are filled with flakes of the carbon fiber, it is difficult to determine the perforation of the projectile. Therefore, whether the projectile perforated the CFRP plate or not was decided by the craters on a copper plate installed behind the CFRP plate. After the impact, peeling along the
fiber direction was observed on the surface of the CFRP plate. Moreover, internal delamination was generated near the surface. Finally, a ballistic limit equation of CFRP plates of 2 to 5 mm in
thickness was calculated on the basis of the Cour-Palais equation. The ballistic limit equation was
in good agreement with the test results
Effects of high-speed impacts on CFRP plates for space applications
No full textIn the framework of a collaboration between the Center of Studies and Activities for Space of the University of Padova (CISAS-UPD) and the Japan Aerospace Exploration Agency (JAXA), 45 hypervelocity impact experiments were realised on Carbon Fibre Reinforced Plastic samples (CFRP) having nominal thickness of 2.3, 3.5 and 4.3 mm. The impact tests were made with aluminium spheres of 0.8, 1.5, 1.9, 2.3 and 2.9 mm, at velocities between 2 and 5 km/s.
After a preliminary post-impact inspection of the targets, ballistic limit equations were developed using a new procedure which permits to estimate the uncertainty in the failure predictions starting from the measurement of the projectile entry crater. Then, in case of sample perforation and consequent ejection of fragments, high-speed shadowgraphs of the debris cloud were analysed to qualitatively describe the evolution of the impact damage, together with its basic features
Ballistic limit of thin CFRP plates
No full textJAXA (Japan Aerospace Exploration Agency) has carried out the hypervelocity impact tests for carbon fiber reinforced plastic (CFRP) plates together with CISAS (Centre of Studies and Activities for Space), University of Padova. Quasi-isotropic CFRP plates of 2.3, 3.5, and 4.7 mm in thickness were tested. Aluminum sphere of 0.8 to 2.9 mm in diameter was used as a projectile. The projectile was launched in a velocity range of 2 to 5 km/sec. The projectile impacted on the target in the normal direction. After the impact, peeling along the fiber direction was observed on the surface of the target. Moreover, delamination was generated near the surface of the target. A ballistic limit equation for CFRP was calculated by modifying the Cour-Palais equation. The ballistic limit equation for CFRP showed the good agreement with the test results
Debris Impact on CFRP-AL Honeycomb Sandwich Structure
No full textIn order to do risk assessments of debris impacts on unmanned spacecraft, it is necessary to investigate damage of honeycomb sandwich structures caused by debris impacts. However, the
study of the honeycomb sandwich panel with CFRP face sheets has not been sufficiently performed. The purpose of this study is to investigate hypervelocity impact phenomena of CFRPAL
honeycomb sandwich structure. Hypervelocity impact tests were performed with a two-stage light gas gun at University of Padova. Three kinds of CFRP-AL honeycomb sandwich panels which are frequently used as a material of a spacecraft structure were tested. The cell size and the core thickness were varied. Aluminum spheres, 0.8 mm in diameter, were used as projectiles. The tests were performed at a velocity range between 2 and 5 km/sec. After the tests, the projectiles perforated all targets. The perforation holes on the panels were measured, and ultrasonic inspection was performed. The area of the perforation holes of the panel were increased with the impact velocity. The core size of the honeycomb core did not influence the relationship between the hole and the impact velocity. Impacts of the projectile on the foil of honeycomb cell caused
heavy damage to a face sheet of the opposite side of the impact surface
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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