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Mode-II fracture behaviour of aerospace-grade carbon fibre/epoxy composites interleaved with thermoplastic veils
No full textThermoplastic veils based on Polyethylene-terephthalate (PET), Polyphenylene-sulfide (PPS) and Polyamide-12 (PA) fibres (∼10μm in diameter) were used to interlay unidirectional (UD), non-crimp fabric (NCF) and 5-Harness satin weave (5H) carbon fibre laminates. The PET and PPS veils remained in a fibrous form and the PA veils melted during the laminate curing process. The results of an end-loaded split test demonstrated significant improvements in the mode-II fracture performance in all cases. In general, interlaying thermoplastic veils was most efficient for toughening the UD laminates, with reduced improvements observed for the 5H and NCF laminates, respectively. The main toughening mechanism of the intact PET and PPS veils was thermoplastic fibre bridging. The melted PA veils mainly improved the fracture toughness of the epoxy at the mid-plane. The different toughening mechanisms of the veils, combined with different fracture mechanisms between the UD, NCF and 5H laminates, resulted in significantly different toughening levels
Interlaminar fracture toughness of aerospace-grade carbon fibre reinforced plastics interleaved with thermoplastic veils
No full textThis work investigates the toughening performance of thermoplastic veils when used to interlay aerospace-grade CFRPs. Veils based on Polyethylene-terephthalate (PET), Polyphenylene-sulfide (PPS) and Polyamide-12 (PA) fibres (~10 μm in diameter) were used as interlayers of unidirectional (UD), non-crimp fabric (NCF) and 5-Harness satin weave (5H) carbon fibre/epoxy laminates. During a hot curing process of the laminates, the PET and PPS veils remained in a fibrous form, and the PA veils melted. This resulted in different toughening mechanisms, i.e. interlaying the PET and PPS veils introduced extensive thermoplastic fibre bridging, and adding the PA veils improved the fracture toughness of the epoxy matrix. The different toughening mechanisms of the veils, together with the different fracture mechanisms of the laminates, dramatically affected the toughening levels. In general, the PET and PPS veils were more effective for toughening the UD laminates, and the PA veils were superior for the NCF and 5H laminates
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
Adhesion Improvement of Thermoplastics-Based Composites by Atmospheric Plasma and UV Treatments
Full text linkThe present work is concerned with adhesive bonding of thermoplastic composites used in general aerospace applications, including polyphenylene sulfide (PPS), polyetherimide (PEI) and polyetheretherketone (PEEK) carbon fibre composites. Three different surface treatments have been applied to the PEEK, PPS and PEI-based composites in order to enhance the adhesion: atmospheric plasma, ultraviolet radiation (UV) and isopropanol wiping as a control. Water contact angles and free surface energies were measured following the standard experimental procedure based on the employment of three different liquid droplets. Infrared spectroscopy and X-ray photoelectron spectroscopy (XPS) were subsequently performed to characterize the surface chemistry of the samples after treatment. The single lap joints were manufactured and bonded by an Aerospace grade epoxy-based film adhesive originally developed for use on metals but with the ability to bond treated thermoplastics to good strength (supplied by Henkel Ireland). Quasi-static (QS) tests were conducted. The lap shear strength was evaluated, and the failure mechanisms of the different joints were examined for the range of surface treatments considered. It was found that the performances of the PEEK and PPS joints were considerably improved by the plasma and UV treatments resulting in cohesive and delamination failures, while PEI was unaffected by the plasma and UV treatments and performed very well throughout
Rapid surface activation of carbon fibre reinforced PEEK and PPS composites by high-power UV-irradiation for the adhesive joining of dissimilar materials
Full text linkCarbon fibre reinforced poly-etherether-ketone (PEEK) and poly-phenylene-sulfide (PPS) composites were rapidly surface-treated by high-power UV light, and then adhesively bonded to aluminium 2024-T3 and carbon fibre/epoxy composites. The results of a single lap-shear joint test demonstrated that a UV-treatment lasting for 5 s was sufficient to prevent joint failure occurring at the composite/adhesive interfaces in all cases, e.g. it increased the failure strength of the PPS composite/aluminium joints from 11.1 MPa to 37.5 MPa. Moreover, the composite/adhesive interfaces performed well upon an exposure of the joints to an environment of high humidity and temperature for 8 weeks. Additionally, an investigation lasting for 6 months showed no degradation of the surface functionalisation from UV-irradiation. Overall, this work highlights high-power UV-irradiation a very promising method for surface preparation of thermoplastic composites (TPCs) for adhesive joining, i.e. TPC adhesive joints with excellent structural integrity can be obtained by using this rapid, eco-friendly and low-cost surface-treatment method
Improving the electrical conductivity and fracture toughness of carbon fibre/epoxy composites by interleaving MWCNT-doped thermoplastic veils
Full text linkPolyethylene terephthalate (PET) veils doped with and without multi-walled carbon nanotubes (MWCNT) were used to interlay a unidirectional carbon fibre/epoxy composite. The electrical and fracture properties of the laminates were studied. Significant improvements in the Mode-I fracture energy (GIC) and Mode-II fracture energy (GIIC) of the laminates were observed for interlaying the original PET veils. This was associated with a considerable drop in the electrical conductivity. Doping a small amount of MWCNTs on the PET interlayers strikingly improved the electrical conductivity of the laminates, especially in the through-thickness direction. However, it also resulted in moderate decreases in GIC and GIIC. Interestingly, this was caused by an improved PET fibre/epoxy adhesion due to the presence of the MWCNTs on the PET fibres, that restrained the PET fibre bridging in the fracture process. The experimental results demonstrated the potential of developing both highly electrically conductive and tough laminates by interlaying MWCNT-doped thermoplastic veils
Evaluation of the conservation status of the croatian posavina horse breed based on pedigree and microsatellite data
Full text linkThe Croatian Posavina horse (CPH) is native Croatian breed under a conservation program and under various programs of economic use (ecosystem services, agrotourism, and meat produc-tion). The aim of this study was to analyze the status of the CPH population through an analysis of their pedigree (28,483 records), phenotype (292 licensed stallions, 255 mares), and genetic structure (292 licensed stallions). The average generation interval was 8.20 years, and the number of complete generations was 1.66. The effective number of founders and ancestors was 138 and 107, respectively, with a ratio of 1.29, and the genetic conservation index was 4.46. As for the morphometric char-acteristics, the average withers height of the stallions was 142.79 cm, the chest circumference was 194.28 cm, and the cannon bone circumference was 22.34. In mares, the withers height, chest, and cannon bone circumference were lower (139.71 cm, 190.30 cm, and 20.94 cm, respectively). Genetic microsatellite analysis of the 29 sire-lines showed high genetic diversity, expressed as the mean allele number (7.7), allele richness (4.0), and expected heterozygosity (0.740). There was no evidence of high inbreeding or a genetic bottleneck. The genetic and phenotypic data indicate that the CPH is an important and diverse reservoir of genetic diversity and can be conserved because of its special characteristics (adaptability)
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