Analisi numerica del processo di decoesione nei laminati compositi rinforzati lungo lo spessore

Numerical modeling of masonry structures reinforced by FRP plate/sheets

Simulazione numerica della risposta di travi in legno lamellare rinforzate lungo lo spessore con barre di GFRP

Le travi in legno lamellare sono costituite da singole lamine assemblate attraverso giunti adesivi longitudinali e trasversali. Una tecnica per migliorare le propriet`a meccaniche di tali giunti consiste nell’inserimento di rinforzi trasversali in forma di barre FRP. La presente memoria indaga il comportamento di travi lamellari sia da un punto di vista sperimentale che numerico, attraverso la formulazione di un semplice modello di interfaccia bifase (giunto adesivo e rinforzo).

Numerical analysis of delamination in through-thickness reinforced composite laminates

Composite laminates show a high vulnerability to out-of-plane actions, responsible for localized damage between two adjacent laminae, i.e. delamination phenomenon. A recent technological solution to improve the strength of the composite laminates in the thickness direction consists in inserting through-thickness reinforcement. In this paper, the composite delamination is analyzed in the context of non-linear fracture mechanics by an original two-phase interface model able to describe the anisotropic elastic and post-elastic mechanical response given by the presence of the reinforcement fibres. The two phases (adhesive joint or matrix of the composite and the reinforcement) are characterized…

Minimum bond length and size effects in FRP–substrate bonded joints

Abstract The load transfer mechanism between the fibre-reinforced polymer (FRP) materials and the substrate plays a crucial role in the overall response of retrofitted structural members. The FRP–support material interface can be studied by using pull tests in which a reinforcement plate is bonded to a prism and subjected to a tensile force. The experimental results obtained regard the assembly (FRP strip-support block), then a central problem is how to carry out the interface constitutive laws and the related parameters. The principal objective of the present paper is to contrive a procedure which, for a fixed interface constitutive law, permits to derive the interface mechanical parameter…

Delamination study of through-thickness reinforced composite laminates via two-phase interface model

A technique to enhance the strength of the composite laminates in the thickness direction consists in inserting through-thickness reinforcement, by which the potential delamination crack faces are bridged in order to increase the interlaminar fracture strength. In this paper, the composite delamination is analyzed in the context of non-linear fracture mechanics making use of the interface concept. The presence of the reinforcement fibres provides an anisotropic elastic and post-elastic mechanical response, which herein is described by an original two-phase interface model. The two phases, namely the adhesive joint (or matrix of the composite) and the reinforcement, are characterized by thei…

Minimum bond length and size effects in FRP-substrate bonded joints

The load transfer mechanism between the fibre-reinforced polymer (FRP) materials and the substrate plays a crucial role in the overall response of retrofitted structural members. The FRP–support material interface can be studied by using pull tests in which a reinforcement plate is bonded to a prism and subjected to a tensile force. The experimental results obtained regard the assembly (FRP strip-support block), then a central problem is how to carry out the interface constitutive laws and the related parameters. The principal objective of the present paper is to contrive a procedure which, for a fixed interface constitutive law, permits to derive the interface mechanical parameters from th…

Size effect in FRP-substrate material bonded joints

VALUTAZIONE DELLA RESISTENZA DI ADESIONE E DELLA LUNGHEZZA EFFICACE DI INCOLLAGGIO NEI GIUNTI ADESIVI TRAMITE LE LEGGI DELL’EFFETTO SCALA

In recent years, growing attention has been paid by researchers in structural mechanics to bonded joints in order to provide theoretical and numerical tools for better understanding the interfacial bonding/debonding phenomena. The research efforts in this area regard the formulation of reliable bond-slip models based on experimental data coming from laboratory tests performed on small specimens [1, 2]. As reported in [3], the mechanical quantities characterizing any interface constitutive law can be derived from the results of the experimental pull tests by a simple procedure making use of a schematization of the structural problem. The application to some single lap joint tests, carried ou…

Delamination study of Z-pinned composite laminates via two-phase interface model.

One of the most effective technique, developed over the last decade, to enhance the strength of the composite laminates in the thickness direction (z-direction), is the through-thickness reinforcement in form of stitching [2], [4] or short rods inserting [3]. These reinforcing fibres, providing direct closure tractions to the potential delamination crack faces (bridging effect), increase the interlaminar fracture toughness. The reinforcement system can be applied extensively to the composite laminate or restricted to those critical structural zones that are subjected to high interlaminar stresses. The through-thickness reinforcement is also used in composite-composite assemblages where, cou…

Modello di interfaccia bifase per la descrizione dei fenomeni di decoesione nei materiali compositi

Numerical analysis of the mechanical response of wood glulam beams reinforced through the thickness by FRP rods

The modern use of through-thickness reinforcement in wood glulam (glued laminated) beams, bridging the potential delamination crack faces, has shown to be an effective technological solution to improve their interlaminar fracture strength. In this paper, the behaviour of wood glulam beams is investigated from an experimental and numerical point of view, comparing the mechanical response of unreinforced and reinforced (by FRP rods) beams subjected to four points bending tests. For the numerical analysis, a simple two-phases (joint and reinforcement) interface model has been formulated and implemented in a finite element code. In particular, the classical interface model for adhesive joint, a…