Stiffness constants prediction of nanocomposites using a periodic 3D-FEM model

Predictive models, which enable the prediction of nanocomposite properties from their morphologies and account for polymer orientation, could greatly assist the exploitation of this new class of materials in more diversified and demanding market fields. This article focuses on the prediction of effective elastic properties (Young's moduli) of polymer nanocomposite films (copolyamide-6/nanoclay) using 3D analytical (based on the Mori-Tanaka theory) and 3D finite element (FE) models. The analytical model accounts for the orientation of polymer chains induced by drawing. 3D FE model exploits the representative volume element concept and accounts for the nanocomposite morphology as determined from transmission electron microscopy experiments. Model predictions were compared with experimental results obtained for nanocomposite films produced by means a pilot-scale film blowing equipment and collected at different draw ratios

Experimental evaluation of the long-term creep deformations of epoxy resin

Abstract Adhesively bonded structures are widely used in many engineering fields for new structures and strengthening of existing ones. The failure of these joints are in some cases caused by long-term deformations. In this paper, an in house made experimental setup for investigating the creep behavior of epoxy resin specimens is presented. The test equipment consists of both conventional apparatus and a non-contact optical technique, Digital Image Correlation (DIC). Several tests were performed at different temperatures and the corresponding results were used for creep master curve construction by means of time-temperature superposition principle (TTSP)

rapporti tra processo tributario e processo penale

L'analisi dell'evoluzione storica dei rapporti tra processo tributario e processo penale implica una ricognizione analitica delle normative succedutesi nel tempo e sfocia nella considerazione critica delle implicazioni processuali connesse all'introduzione del radddoppio dei termini di cui al D.L. n. 223/200

A general approach for modelling the peeling of a flexible tape from an elastic substrate

The tape-substrate detachment mechanics has been extensively studied in the last decades. The most popular approach to this topic consists of finding the detachment load through a balance between the potential and the adhesion energies within the well-established Griffith framework of the elastic fracture mechanics. This work shows how it is possible to obtain, in general conditions, the energy release rate of a flexible tape with elastic substrate system, with no allowance for the elastic energy. In particular, a simple expression is given for energy release rate as a function of internal forces and rotation at a single section of the tape. Apart from the theoretical interest, the method provides a numerical evaluation of the energy release rate suitable when tackling large displacements fields. Such evaluation turns out to be faster and more accurate of those available even in the recent literature. Further, the proposed methodology can be used as an efficient data reduction technique for experimental determination of the tape – substrate adhesion energy. Several evaluations from literature of the energy release rate and the detaching load, encompassing debonding of configurations ranging from thin tape to stiff lamina, turn out to be degenerated cases of our general expression

Comparison of DBEM and FEM Crack Path Predictions in a notched Shaft under Torsion

The rather complex 3D fatigue crack growth behaviour of two anti-symmetric ‘‘bird wing” cracks, initiated from the two crack front corner points of a notched shaft undergoing torsion, is investigated by the Dual Boundary Element Method (DBEM) and by the Finite Element Method (FEM). Different criteria for the crack path assessment (Minimum Strain Energy Density, Maximum Principal Stress and Approximate Energy Release Rate) and for the Stress Intensity Factor (SIF) evaluation (COD and J-integral) are adopted. The SIF’s and the crack path, calculated by such different approaches, turn out to be well consistent with each other. Moreover the simulated crack path qualitatively agrees with experimental findings available from literature

DISPOSITIVO PER PROVE DI RESISTENZA ALLA FRATTURA IN MODO III SU GIUNZIONI INCOLLATE

L’invenzione concerne un dispositivo per prove di resistenza alla frattura su giunzioni incollate, che sia in grado di selezionare unicamente il modo III, in maniera da non dover ricavare i valori di resistenza a posteriori dopo aver utilizzato più dispositivi con tecniche diverse