Search results for "sandwich"
showing 10 items of 62 documents
Penalized logistic regression for small or sparse data: interval estimators revisited
2015
This paper focuses on interval estimation in logistic regression models fitted through the Firth penalized log-likelihood. In this context, many authors have claimed superiority of the Likelihood ratio statistic with respect to the (wrong) Wald statistic via simulation evidence. We re-assess such findings by detailing the inferential tools also including in the comparisons the (right) Wald statistic and other statistics neglected in previous literature. In particular, we assess performances of the CIs estimators by simulation and compare them in a real data set. Differently from previous findings, the Likelihood ratio statistic does not appear to be the best inferential device in Firth pena…
ANALISI DEL COMPORTAMENTO MECCANICO DI SANDWICH ECO-COMPATIBILI RINFORZATI CON FIBRE NATURALI
2015
The increasing environmental sensitivity in many industrial fields, from automotive to aeronautics to naval field, has led to an increasing demand of new bio-materials or renewable structural materials. In order to give a contribution to the design of eco-compatible structural materials, in this work new sandwich materials constituted by a core made by balsa and skins made by a composite material made by a “green” epoxy reinforced by agave fibers extracted from striated and americana agave obtained in Sicily by a proper research program financed by European founds. Previous theoretical analysis followed by systematical experimental analysis of the core, of the skins and the of the sandwich,…
Analysys and optimization of an end double-lap bonded joint for GFRP composite sandwich panels
2022
Although the best configuration of the joints used to connect a common GFRP sandwich panel with the main structures is the adhesively bonded one, that permit high static and fatigue performances as well as to avoid stress concentrations, mechanical or hybrid joints are still widely used in the industrial field. After a preliminary theoretical design, the optimal configuration of an end adhesively bonded double-lap joint constituted by a simple insert as internal adherent and the same face sheets as external adherent, has been researched. In detail, several experimental tests and successive numerical simulations under tensile and bending loading, performed by varying the main influence para…
ANALISI DEL COMPORTAMENTO AD INDENTAZIONE IN TRAVI SANDWICH IN COMPOSITO CON ANIMA IN SCHIUMA POLIMERICA
2010
Nel presente lavoro si propone una estensione dei modelli basati sulla teoria delle travi vincolate su una fondazione cedevole di tipo Winkler per lo studio del comportamento ad indentazione di travi sandwich in schiuma polimerica sollecitate da carichi concentrati. L’approccio proposto è in grado di considerare schiume polimeriche aventi comportamento a compressione di tipo non lineare. Sono derivate soluzioni analitiche in forma chiusa della curva di indentazione per anime in schiuma polimerica il cui comportamento a compressione è approssimabile con un andamento bi-lineare. In tal modo è possibile considerare comportamenti di softening o hardening della schiuma nel tratto post-elastico. …
A New Thermal Theory for Thermo-Mechanical Analysis of Composites
2009
The use of laminated and sandwich construction to achieve multi-functional objectives within a single structure continues to increase. It is especially desirable to use laminated construction in structures exposed to thermal loading, where heat resistant coating materials may be bonded to traditional structural materials. Design of such structures requires an accurate analysis of stresses induced by thermal as well as mechanical loads. A novel laminated plate theory and 3D finite element model based on first-order zig-zag sublaminate approximations are presented for thermal stress analysis of composite laminates and sandwich plates. The finite element is developed with the topology of an ei…
Investigation on the behaviour of fully thermoplastic composite sandwich beams under concentrated loads
2009
The recent development of new low cost manufacturing processes adopting thermoplastic matrices in the production of structural long fibre reinforced laminates is fostering an increasing interest towards this class of materials. The automotive sector in particular is attracted by the high energy absorbing, damage tolerance performances and manufacturing and recycling potentials of structural thermoplastic composites. In this study a number of fully thermoplastic sandwich beams have been manufactured in order to investigate flexural and shear rigidity performances as well as the indentation behavior under static concentrated loads.
OTTIMIZZAZIONE DI UNA GIUNZIONE INCOLLATA A DOPPIA SOVRAPPOSIZIONE PER SANDWICH IN COMPOSITO
2016
Grazie alle peculiari performances meccaniche, quali soprattutto l’elevata resistenza a flessione unita ad un basso peso specifico, le strutture sandwich in composito sono sempre più frequentemente utilizzate nella moderna progettazione industriale. Nel presente lavoro, considerando un composito sandwich con skins in vetroresina e core in PVC espanso, è stato eseguito uno studio numerico e sperimentale al fine di individuare la configurazione ottimale di una giunzione incollata a doppia sovrapposizione avente quali aderendi esterni le stesse skins del sandwich e aderendo interno costituito da un inserto in metallo o in composito. In dettaglio, previa preliminare ottimizzazione teorica della…