1,720,989 research outputs found
Problems involved in fracture mechanics characterization of rubber-modified glassy polymers, using double torsion
No full textAn evaluation of double torsion testing of polymers by visualization and recording of curved crack profile
No full textLa certificazione di qualità dei materiali FRP a margine delle recenti Istruzioni per la Progettazione, l’Esecuzione ed il Controllo di Interventi di Consolidamento Statico mediante l’utilizzo di Compositi Fibrorinforzati (CNR-DT 200/2004)
No full text
EFFECTS OF MATRIX VISCOELASTICITY ON INTERLAMINAR FRACTURE TOUGHNESS OF ACRYLIC/CARBON FIBRE COMPOSITES
No full textCaratterizzazione meccanica di materiali compositi per il consolidamento di strutture civili
No full textLo scopo del presente lavoro è di indagare gli effetti della struttura del composito (FRP) sulle proprietà meccaniche del composito stesso. Infatti, la grammatura del tessuto, la direzione delle fibre, la quantità di resina di impregnazione influiscono sulla resistenza meccanica in modo significativo. La sperimentazione, tutt'ora in corso, prevede lo sviluppo di tecniche standard di caratterizzazione del materiale composito per applicazioni su strutture civili
Mesoscale mechanical modelling and experimental measurements of textile composite reinforcements
No full textWoven fibrous textiles as reinforcement of composite materials have received considerable attention in many different industrial applications, due to their improved formability and mechanical properties. Predictive tools are mandatory to avoid time-consuming experimental measurements and to predict and assess the mechanical behaviour of such dry textiles upon variation of several parameters. Their mechanical features have considerable influence during complex shape forming process, in the initial step of the composite manufacturing, and on the mechanical behaviour of final composite components. In this context, the present study deals with the mechanical behaviour of fibrous textiles as reinforcements for composites. A glass plain weave and a hybrid PET/aramid/PET tetraxial textiles were considered. The tetraxial interlacement has warp, weft, and two diagonal yarns oriented at symmetrical angles (typically ±45°) with respect to the warp direction. The aims of the study were: (i) to experimentally observe the deformation and to measure some mechanical properties of the textile reinforcements; (ii) to numerically predict the nonlinear behaviour of the woven fibrous fabrics for any in-plane loading conditions; (iii) to compare the finite element (FE) modelling results to the experimental observations of biaxial tensile and inplane shear loadings. The experimental activities were focused mainly on uniaxial and biaxial extension tests, the latter with different ratio R of the warp to weft displacement rates. Besides, out of plane bending was investigated by cantilever beam test. The numerical study was based on a hyperelastic constitutive model for the yarns material [4]. Assuming the repetitive nature of the considered textiles, the simulation were focused on the Representative Volume (RV), namely meso-scale modelling. The comparison of experimental measurements and numerical predictions highlights the accuracy of the hyperelastic model to predict the nonlinear behaviour of the fabric for any loading condition and to provide the proper numerical model for further optimization investigations of woven fibrous reinforcement
Effects of matrix viscoelasticity on interlaminar fracture toughness of acrylic/carbon fibre composites
No full textThe interlaminar fracture toughness of an acrylic resin/carbon fibre composite was studied in relation to the fracture toughness of the matrix. Composites were prepared by infusing the matrix monomers into the fibre stack and then letting the matrix to polymerize in-situ. The deformation rate and temperature dependence of both the plain matrix and the composite were analysed and by applying the time-temperature superposition the crack speed range was extended. The fracture toughness of the composite turned out to be higher than that of the plain matrix indicating that also other mechanisms linked to the presence of the fibres are present in the composite. The fracture toughness of the pure matrix increased with crack speed as it is expected for a viscoelastic material while the composite showed a constant value at varying crack speed. Further investigation is in due course to better analyse the damage mechanisms taking place in the composite during fracture
- …
