Juan Miquel

A plastic damage constitutive model for composite materials

In this paper a generalized elasto-plastic damage model for the analysis of multiphase frictional composite materials is presented. Details of the derivation of the secant and tangent constitutive equations are given. Mixing theory is used to insert the basic constitutive expressions for each substance on the multiphase composite solid. Details of the numerical implementation of the model into a general non-linear finite element solution scheme are presented. Some examples of linear and non-linear behaviour of composites are given.

Numerical simulation of fiber reinforced composite materials: two procedures

Abstract In this work, two methodologies for the analysis of unidirectional fiber reinforced composite materials are presented. The first methodology used is a generalized anisotropic large strains elasto-plastic constitutive model for the analysis of multiphase materials. It is based on the mixing theory of basic substance. It is the manager of the several constitutive laws of the different compounds and it allows to consider the interaction between the compounds of the composite materials. In fiber reinforced composite materials, the constitutive behavior of the matrix is isotropic, whereas the fiber is considered orthotropic. So, one of the constitutive model used in the mixing theory needs to consider this characteristic. The non-linear anisotropic theory showed in this work is a generalization of the classic isotropic plasticity theory (A Continuum Constitutive Model to Simulate the Mechanical Behavior of Composite Materials, PhD Thesis, Universidad Politecnica de Cataluna, 2000). It is based in a one-to-one transformation of the stress and strain spaces by means of a four rank tensor. The second methodology used is based on the homogenization theory . This theory divided the composite material problem into two scales: macroscopic and microscopic scale. In macroscopic level the composite material is assuming as a homogeneous material, whereas in microscopic level a unit volume called cell represents the composite (Tratamiento Numerico de Materiales Compuestos Mediante la teori de Homogeneizacion, PhD Thesis, Universidad Politecnica, de Cataluna 2001). This formulation presents a new viewpoint of the homogenization theory in which can be found the equations that relate both scales. The solution is obtained using a coupled parallel code based on the finite elements method for each scale problem.

Mixing anisotropic formulation for analysis of composites

A general constitutive model adequate for analysis of the thermomechanical response of composite materials is presented. The model is based on the mixture of the basic substances of the composite and allows the evaluation of the interdependence between the constitutive behaviour of different compounding materials. The behaviour of the each compound is modelled by a general anisotropic thermo-elasto-plastic model, termed the ‘base model’. The different base models for each compound are combined using mixing theory to simulate the behaviour of the multiphase material.

A general procedure for deriving symmetric expressions for the secant and tangent stiffness matrices in finite element analysis

The paper presents a general and straightforward procedure based on the use of the strain energy density for deriving symmetric expressions of the secant and tangent stiffness matrices for finite element analysis of geometrically non-linear structural problems. The analogy with previously proposed methods for deriving secant and tangent matrices is detailed. The simplicity of the approach is shown in an example of application.

A Numerical-Experimental Method for Characterizing Recycled Asphalt Mixtures

ABSTRACT Experimental techniques usually employed in the characterization of conventional mixes are not able to clearly describe some specific properties of the recycled mixes, which are determinant in the materials mechanical response like cracking strength or tenacity. These new specific properties demands new methods of testing to know the really conditioning mechanical variables taking part in the process, so that being able to characterize and design new recycled mixes in an optimum way. In this paper, the direct tensile test is analyzed as a suitable method for evaluating the properties of recycled asphalt mixtures for different percentages of reclaimed asphalt pavement. A constitutive formulation has been developed to simulate the experimental results and can be used in conjunction with the experimental analysis of the recycled asphalt properties to provide an accurate characterization of the material.

Advances in the DEM and Coupled DEM and FEM Techniques in Non Linear Solid Mechanics

In this chapter we present recent advances on the Discrete Element Method (DEM) and on the coupling of the DEM with the Finite Element Method (FEM) for solving a variety of problems in non linear solid mechanics involving damage, plasticity and multifracture situations.