Fiber-reinforced plastic (FRP) plates are usually externally bonded to the tension face of a concrete or steel beam by means of an adhesive layer, leading to a flexural reinforcement for structural elements, with a considerable number of advantages in terms of strength and durability, despite the small changes in weight and dimension of the structural system. However, the use of adhesively bonded external FRP reinforcements exposes the strengthened structure to additional catastrophic failure modes, mainly related to a decrease of ductility. The reinforced system, in fact, becomes vulnerable to debonding failure modes involving the FRP layer, usually associated with the initiation and growth of interfacial cracks at the interface between the adhesive layer and the lower face of the beam [1]. Interfacial debonding is often caused by high concentrations of normal and shear stresses at the end of the bonded plate, or by bonding defects in the application of the FRP reinforcement [2]. The initiation and propagation of interfacial debonding mechanisms critically affect the structural functionality of the structural element, leading in many cases to the global failure of the layered element [3]. A numerical investigation is here carried out, by means of an innovative multi-layer formulation, in order to analyze the onset and propagation of edge debonding for beams strengthened with externally bonded fiber-reinforced composite plates. An innovative mixed mode coupled criterion is adopted to predict debonding initiation accounting for both fracture energies and interfacial stresses and considering different debonding locations across the adhesive layer [4-6]. The subsequent debonding propagation is studied by using a mixed mode fracture criterion. The three physical components of the system, namely the beam, the adhesive layer and the bonded plate, are modeled by means of one or several first-order shear deformable layers, assuming both strong and weak interface formulations for the two physical interfaces (i.e. beam/adhesive and adhesive/plate) and a strong formulation for the mathematical interfaces between layers [7, 8]. Numerical simulations show that the proposed multilayer formulation, implemented by using a multivariable 1D finite element technique, enables to calculate interlaminar stresses and fracture energies in reasonable agreement with results obtained by using a continuum FE model, but with a significantly reduced computational cost. The numerical analyses show that although the accuracy can be improved by using more layers for each components and adopting coupled strong/weak interface formulations, the use of few layers for each components of the strengthened system suffices to obtain an accurate prediction of debonding initiation and propagation. References [1] Rabinovitch, O., 2008. Debonding analysis of fiber-reinforced-polymer strengthened beams: Cohesive modeling versus a linear elastic fracture mechanics approach. Engineering Fracture Mechanics 75, 2842-2859. [2] Rabinovitch, O., 2014. An extended high order cohesive interface approach to the debonding analysis of FRP strengthened beams. International Journal of Mechanical Sciences 81, 1-16. [3] Teng, J. G., Yuan, H., Chen, J. F., 2006. FRP – to – concrete interfaces between two adjacent cracks: theoretical model for debonding failure. Int. J. Solids Struct. 43 (18 and 19), 5750-5778. [4] Leguillon, D., 2002. Strength or toughness? A criterion for crack onset at a notch. European Journal of Mechanics A/Solids 21, 61-72. [5] Greco, F., Leonetti, L., Nevone Blasi, P., 2012. Non-linear macroscopic response of fiber-reinforced composite materials due to initiation and propagation of interface cracks. Engineering Fracture Mechanics 80, 92-113. [6] Greco, F., Leonetti, L., Lonetti, P., 2013. A two-scale failure analysis of composite materials in presence of fiber/matrix crack initiation and propagation. Composite Structures 95, 582-597. [7] Bruno, D., Carpino, R.; Greco, F., 2007. Modelling of mixed mode debonding in externally FRP reinforced beams. Composites Science and Technology 67, 1459-1474. [8] Greco, F., Lonetti. P., Nevone Blasi, P., 2007. An analytical investigation of deboning problems in beams strengthened using composite plates. Engineering Fracture Mechanics 74, 346-372.
Numerical investigation of edge debonding in FRP reinforced beams using a multilayer approach
BRUNO, Domenico;GRECO, Fabrizio;NEVONE BLASI, Paolo
2015-01-01
Abstract
Fiber-reinforced plastic (FRP) plates are usually externally bonded to the tension face of a concrete or steel beam by means of an adhesive layer, leading to a flexural reinforcement for structural elements, with a considerable number of advantages in terms of strength and durability, despite the small changes in weight and dimension of the structural system. However, the use of adhesively bonded external FRP reinforcements exposes the strengthened structure to additional catastrophic failure modes, mainly related to a decrease of ductility. The reinforced system, in fact, becomes vulnerable to debonding failure modes involving the FRP layer, usually associated with the initiation and growth of interfacial cracks at the interface between the adhesive layer and the lower face of the beam [1]. Interfacial debonding is often caused by high concentrations of normal and shear stresses at the end of the bonded plate, or by bonding defects in the application of the FRP reinforcement [2]. The initiation and propagation of interfacial debonding mechanisms critically affect the structural functionality of the structural element, leading in many cases to the global failure of the layered element [3]. A numerical investigation is here carried out, by means of an innovative multi-layer formulation, in order to analyze the onset and propagation of edge debonding for beams strengthened with externally bonded fiber-reinforced composite plates. An innovative mixed mode coupled criterion is adopted to predict debonding initiation accounting for both fracture energies and interfacial stresses and considering different debonding locations across the adhesive layer [4-6]. The subsequent debonding propagation is studied by using a mixed mode fracture criterion. The three physical components of the system, namely the beam, the adhesive layer and the bonded plate, are modeled by means of one or several first-order shear deformable layers, assuming both strong and weak interface formulations for the two physical interfaces (i.e. beam/adhesive and adhesive/plate) and a strong formulation for the mathematical interfaces between layers [7, 8]. Numerical simulations show that the proposed multilayer formulation, implemented by using a multivariable 1D finite element technique, enables to calculate interlaminar stresses and fracture energies in reasonable agreement with results obtained by using a continuum FE model, but with a significantly reduced computational cost. The numerical analyses show that although the accuracy can be improved by using more layers for each components and adopting coupled strong/weak interface formulations, the use of few layers for each components of the strengthened system suffices to obtain an accurate prediction of debonding initiation and propagation. References [1] Rabinovitch, O., 2008. Debonding analysis of fiber-reinforced-polymer strengthened beams: Cohesive modeling versus a linear elastic fracture mechanics approach. Engineering Fracture Mechanics 75, 2842-2859. [2] Rabinovitch, O., 2014. An extended high order cohesive interface approach to the debonding analysis of FRP strengthened beams. International Journal of Mechanical Sciences 81, 1-16. [3] Teng, J. G., Yuan, H., Chen, J. F., 2006. FRP – to – concrete interfaces between two adjacent cracks: theoretical model for debonding failure. Int. J. Solids Struct. 43 (18 and 19), 5750-5778. [4] Leguillon, D., 2002. Strength or toughness? A criterion for crack onset at a notch. European Journal of Mechanics A/Solids 21, 61-72. [5] Greco, F., Leonetti, L., Nevone Blasi, P., 2012. Non-linear macroscopic response of fiber-reinforced composite materials due to initiation and propagation of interface cracks. Engineering Fracture Mechanics 80, 92-113. [6] Greco, F., Leonetti, L., Lonetti, P., 2013. A two-scale failure analysis of composite materials in presence of fiber/matrix crack initiation and propagation. Composite Structures 95, 582-597. [7] Bruno, D., Carpino, R.; Greco, F., 2007. Modelling of mixed mode debonding in externally FRP reinforced beams. Composites Science and Technology 67, 1459-1474. [8] Greco, F., Lonetti. P., Nevone Blasi, P., 2007. An analytical investigation of deboning problems in beams strengthened using composite plates. Engineering Fracture Mechanics 74, 346-372.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
