An X–FEM Technique for Modeling the FRP Strengthening of Concrete Arches with a Plastic–Damage Model; Numerical and Experimental Investigations

In this paper, an enriched–FEM method is presented based on the X-FEM technique by applying a damage–plasticity model to investigate the effect of FRP strengthening on the concrete arch. In this manner, the damage strain is lumped into the crack interface while the elastic and plastic strains are employed within the bulk volume of element. The damage stress–strain relation is converted to the traction separation law using an acoustic tensor. The interface between the FRP and concrete is modeled using a cohesive fracture model. The X-FEM technique is applied where the FE mesh is not necessary to be conformed to the fracture geometry, so the regular mesh is utilized independent of the position of the fracture. The accuracy of the proposed plastic-damage model is investigated under the monotonic tension, compression, and cyclic tension loading. Furthermore, the accuracy of the cohesive fracture model is investigated using the experimental data reported for the debonding test. In order to verify the accuracy of the proposed computational algorithm, the numerical results are compared with those of experimental data obtained from two tests conducted on reinforced concrete arches strengthened with FRP. Finally, a parametric study is performed by evaluating the effects of high to span ratio, longitudinal reinforcement ratio, and strengthening method.

CONTRIBUIÇÕES AO ESTUDO DE MICROESTRUTURAS REFORÇADAS [Contributions to the Study of Reinforced Microstructures]

RESUMO: Este artigo trata da análise da microestrutura de materiais compósitos com matriz metálica (CMM), os quais têm grande aplicabilidade na Engenharia Estrutural. Para isso, são considerados os processos dissipativos de plastificação, que ocorrem na matriz, e de descolamento, que ocorrem na região de interface matriz/inclusão, onde a influência de tais processos na resposta macroscópica do material será investigada. Para as simulações numéricas do comportamento estrutural de CMM, o modelo de von Mises é utilizado na modelagem da matriz e um modelo de fratura coesiva é utilizado na simulação do processo de descolamento na interface. A inclusão é considerada elástica com grande rigidez. Contudo, os processos dissipativos que ocorrem na microestrutura e que repercutem no comportamento macromecânico do material são analisados através de uma modelagem na microescala utilizando um processo de homogeneização baseado no conceito de Elemento de Volume Representativo (EVR) e no Método dos Elementos Finitos (MEF). A tensão e deformação são médias volumétricas dos respectivos campos microscópicos sobre o EVR. O objetivo geral é verificar as potencialidades e limitações do emprego da modelagem proposta para futuros aperfeiçoamentos de compósitos de matriz metálica para aplicação na engenharia.ABSTRACT: This paper deals with the analysis of the microstructure of metal matrix composites (MMC) and its application in Structural Engineering. For this reason, it is considered the dissipative processes related to plasticity, which occurs in the matrix, and the phase debonding that occurs in the matrix/inclusion interface region, where the influence of such processes on the macroscopic response of the material will be investigated. For the numerical simulations of the MMC structural behavior, the von Mises model will be used in the modeling of the matrix and a cohesive fracture model will be used in the simulation of the phase debonding process. Inclusion will be considered elastic with high rigidity. However, the dissipative processes that occur in the microstructure and that affect the macromechanical behavior of the material will be analyzed through a microscale modeling using a homogenization process based on the concept of Representative Volume Element (RVE) and the Finite Element Method (FEM). The strain and stress are volumetric average of the respective microscopic fields on the EVR. The major goal is to verify the potentialities and limitations of the use of the proposed modeling for future improvements of metal matrix composites to apply in engineering.

Multiscale Analysis of Structures Composed of Metal Matrix Composites Considering Phase Debonding

Multiscale analyses considering the stretching problem in plates composed of metal matrix composites (MMC) have been performed using a coupled BEM/FEM model, where the boundary element method (BEM) and the finite element method (FEM) models, respectively, the macrocontinuum and the material microstructure, denoted as representative volume element (RVE). The RVE matrix zone behavior is governed by the von Mises elasto-plastic model while elastic inclusions have been incorporated to the matrix to improve the material mechanical properties. To simulate the microcracks evolution at the interface zone surrounding the inclusions, a modified cohesive fracture model has been adopted, where the interface zone is modeled by means of cohesive contact finite elements to capture the effects of phase debonding. Thus, this paper investigates how this phase debonding affects the microstructure mechanical behavior and consequently affects the macrostructure response in a multiscale analysis. For that, initially, only RVEs subjected to a generic strain are analyzed. Then, multiscale analyses of plates have been performed being each macro point represented by a RVE where the macro-strain must be imposed to solve its equilibrium problem and obtain the macroscopic constitutive response given by the homogenized values of stress and constitutive tensor fields over the RVE.