Numerical experimental analysis of hybrid double lap aluminum-CFRP joints

Due to their reliability and ease of assembly, both the adhesively bonded and the mechanical joints are commonly used in different fields of modern industrial design and manufacturing, to joint composite materials or composites with metals. As it is well known, adhesively bonded joints are characterized by high stiffness and good fatigue life, although delamination phenomena localized near the free edges may limit their use, especially for applications where corrosive environments and/or moisture can lead to premature failure of the bonding. In these cases, a possible alternative is given by the well-known mechanical joints. On the contrary, these last joints (bolted, riveted) require a preliminary drilling of the elements to be joined, that may cause localized material damage and stress concentration, especially for anisotropic laminates characterized by high stress concentration factors and easy drilling damaging, with significant decrease of the load-carrying capacity of the joined elements. In order to exploit the advantages of the bonded joints and those of the mechanical joints, both industrial manufacturing and research activity have been focused recently on the so called hybrid joints, obtained by the superposition of a mechanical joint to a simple adhesively bonded joint. In order to give a contribution to the knowledge of the mechanical behavior of hybrid bonded/riveted joints, in the present work a numerical–experimental study of bonded/riveted double-lap joints between aluminum and carbon fiber reinforced polymer (CFRP) laminates, has been carried out. It has permitted to highlight both the static and the fatigue performance of such joints obtained by using aluminum and steel rivets, as well as to known the particular damage mechanisms related also to the premature localized delamination of the CFRP laminate due to the riveting process

STUDIO NUMERICO-SPERIMENTALE DI GIUNZIONI IBRIDE A DOPPIA SOVRAPPOSIZIONE CFRP-ALLUMINIO

The adhesively bonded joints and the mechanical joints between structural components made by composite materials or between elements made by composite and metal, are commonly used in different fields of modern industrial design and manufacturing, since they are characterized by economy, reliability and ease of assembly. The bonded joints are characterized by high stiffness and fatigue life, although delamination phenomena localized near the edges of attack of the adherends may limit their use, especially in particular applications where corrosive environments and humidity can lead to premature failure. In these cases, a possible alternative is offered by the well known riveted joints. On the contrary, the riveted joints require a preliminary drilling of the elements to be joined and, consequently, may cause localized material damage, especially in presence of strongly anisotropic laminates which are characterized by high stress concentration. In the present work a numerical and experimental study of hybrid double-lap joints between aluminum and CFRP laminates, have permitted to highlight both the static and the fatigue performance of such joints, also with reference to the particular damage mechanism of the adhesive layer and to the interlaminar damage of the CFRP, due to the riveting process

Valutazioni tecniche ed economiche sull'uso degli inseguitori solari

I processi di antropizzazione connessi allo sviluppo del settore energia hanno determinato delle “impronte” sul nostro pianeta ormai indelebili. Non resta che provare a ridurre i consumi energetici e affidare la produzione dell’energia ad un mix equilibrato di fonti. In questo contesto, con particolare riferimento alla produzione dell’energia elettrica, lo sfruttamento della risorsa solare ha assunto un ruolo di primo ordine. Gran parte delle attività di ricerca e sviluppo del settore si è concentrata sulle tecniche e sulle metodologie innovative di conversione della fonte in energia elettrica. Accanto a queste, a parità di tecnologia di conversione adottata, altre attività di ricerca e sviluppo sono state indirizzate alla ottimizzazione della produzione di energia elettrica mediante “concentrazione” della radiazione solare nel punto di collocazione del dispositivo di conversione ovvero mediante opportuna variazione dell’orientamento del dispositivo rispetto alla direzione della radiazione stessa. Tali attività di ricerca e sviluppo, intraprese dalla comunità scientifica e dal mondo imprenditoriale, certamente favoriranno un migliore sfruttamento della fonte solare e avranno ricadute in tempi diversi. Questo articolo concentra la sua attenzione su gli inseguitori solari, dispositivi di semplice applicazione basati su tecnologie consolidate, la cui diffusa applicazione potrebbe portare, in breve termine, ad un rilevante incremento di producibilità degli impianti fotovoltaici. In particolare, dopo una disamina delle caratteristiche degli inseguitori solari vengono presentati alcuni dati sull’incremento della producibilità degli impianti e alcune considerazioni di ordine tecnico ed economico circa la corretta valutazione della convenienza economica dell’uso di tali dispositivi, che sta alla base dell’effettivo sviluppo del relativo mercato

Assessing niche breadth of vascular plants in Mediterranean temporary wetlands

The high interest in Mediterranean temporary wetlands, which are habitats of Community Interest (3120, 3130 and 3170) in the Habitat Directive 92/43/EEC, is mainly for their characteristic flora or fauna which includes several rare or endangered species. Although the attention on the ecology and biodiversity of these habitats is continuously increasing, the majority of the available studies are based on a qualitative approach or separate statistical analyses of physical, chemical and biodiversity data while little information is available on the relation between plants and environmental features

Valutazione dello stato di conservazione delle "spunnulate" della costa di Porto Cesareo e Nardò (provincia di Lecce) con un approccio vegetazionale

ItLe spunnulate sono doline di crollo sviluppate in rocce arbonatiche. Spesso il loro interno è occupato da un corpo d’acqua di natura salmastra. Presso Nardò e Porto Cesareo sono state censite oltre 60 spunnulate con caratteristiche morfologiche ed ecologiche differenti. Gli scopi del presente studio sono quelli di fornire una descrizione relativa alla distribuzione spaziale delle spunnulate all’interno dell’area di studio e alla vegetazione che le caratterizza. Si vuole, inoltre, fornire un’analisi sui fattori che incidono negativamente sul loro stato di conservazione. Sono stati sviluppati 15 indicatori secondo il modello DPSIR. Per ogni indicatore è stato fornito un giudizio il cui esito è risultato positivo per 2, negativo per 7 e neutro per 6 indicatori.EnThe spunnulate are not very deep cave-collapse sinkholes, developed in carbonate rocks, mainly of Quaternary age. The interior usually is filled with water which is brackish because of its proximity to the sea (NOVEMBRE, 1961a, 1961b; DELLE ROSE and FEDERICO, 2002). In the territories of Porto Cesareo and Nardò, there are about 60 spunnulate with different morphologic and ecologic features. According to Directive 92/43/EEC, these are classified as “Cave not open to the "public” and “Submerged or partially submerged sea caves ”natural habitats of Community importance, as “Coastal lagoons” priority habitat, and as the habitats of some animal species. The aim of this study is to provide a description about the spatial distribution of spunnulate in the subject territory and a description about hydrophytic and riparian vegetation; futhermore, an analysis about factors that negatively affects the conservation status of these habitats. This study carries out vegetation, morphology and environmental stress land data collected through a census at a fine scale. GIS technology is employed for the analysis at a wider scale to make a vegetation map of the spunnulate 500 m geographic surround, through photointerpretation. To evaluate the conservation status of the spunnulate, 15 indicators were developed according to DPSIR model (ORGANISATION FOR ECONOMIC COOPERATION AND DEVELOPMENT, 1993; ENVIRONMENTAL EUROPEAN AGENCY, 1999). For each one, it was provided an assessment wich outcome is: positive for 2, negative for 7 and neutral for 6

Continuum enhancements, line profiles and magnetic field evolution during consecutive flares

During solar flares, magnetic energy can be converted into electromagnetic radiation from radio waves to $\gamma$ rays. Enhancements in the continuum at visible wavelengths give rise to white-light flares, as well as continuum enhancements in the FUV and NUV passbands. In addition, the strong energy release in these events can lead to the rearrangement of the magnetic field at the photospheric level, causing morphological changes in large and stable magnetic structures like sunspots. In this context, we describe observations acquired by satellite instruments (IRIS, SDO/HMI, Hinode/SOT) and ground-based telescopes (ROSA/DST) during two consecutive C7.0 and X1.6 flares occurred in active region NOAA 12205 on 2014 November 7. The flare was accompanied by an eruption. The results of the analysis show the presence of continuum enhancements during the evolution of the events, observed both in ROSA images and in \textit{IRIS} spectra. In the latter, a prominent blue-shifted component is observed at the onset of the eruption. We investigate the role played by the evolution of the $\delta$ sunspots of the active region in the flare triggering, and finally we discuss the changes in the penumbrae surrounding these sunspots as a further consequence of these flares.Comment: 19 pages, accepted for ApJ; some figures are in B/W to accomplish size limit

La conservazione della vegetazione nella riserva di Torre Guaceto

ItNel presente contributo vengono descritte le proposte di interventi finalizzati alla conservazione e la gestione della componente vegetazionale della Riserva dello Stato di Torre Guaceto (Provincia di Brindisi, Regione Puglia). Gli interventi proposti incidono su 3 principali tipi di habitat: le vegetazioni arboree ed arbustive, la zona umida ed il litorale sabbioso. Per ognuno di essi viene analizzato lo stato di conservazione dell’habitat, vengono individuati e descritti i fattori di disturbo, riconducibili quasi sempre ad una causa antropica, i tipi di interventi proposti ed i risultati attesi. Viene inoltre presentata la carta degli habitat d’interesse conservazionistico realizzata sulla base della carta della vegetazione di Torre Guaceto alla scala 1:10000. Gli habitat sono definiti sulla base dei tipi individuati e descritti dalla Direttiva Habitat 43/92/CEE e sulla base della legislazione regionale.EnThis issue deals with suggested operations for the purpose of the conservation and the management of the vegetational component of the Torre Guaceto National Reserve (Brindisi Province, Apulia Region). These operations affect three main habitat types: wood and scrub, wetland and sandy coast. The conservation status is analysed; the disturbances (mainly of them concerning human activity), the proposed operations and the expected outcomes are described for each of these habitat types. Moreover, a map of habitats of some conservation interest is presented; it is based on the Torre Guaceto vegetational map on a scale of 1:10000. Each habitat is defined according to both the 43/92/EEC Habitat Directive and the regional law

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO