ADVANCED SERIAL-PARALLEL MIXING THEORY FOR COMPOSITE MATERIALS ANALYSIS. CONTINUUM BASIS AND FINITE ELEMENT APPLICATIONS

F. RASTELLINI; S. OLLER; O. SALOMON; E. OÑATE

Conferencia; VII International Conference on Computational Plasticity - COMPLAS VII; 2003

In composite materials each component makes the composite behaviour dependent on its own constitutive law according to its volumetric participation. In addition, the components morphological distribution inside the composite became essential, giving better properties to the composite material than its integrant parts. Classical mixing theory (CMT) takes into account the volumetric contribution of components but not its morphological distribution. Therefore, CMT can be useful to obtain basic properties of composite materials assuming parallel behaviour (components with same strains in all directions). This hypothesis is a strong limitation for the use of CMT to predict the behaviour of most composites andconsequently modifications to this theory are always required. To overcome that limitation,in this paper the CMT is reformulated giving place to an Advanced Serial-Parallel MixingTheory, more general and versatile, able to capture automatically the multiple behaviour ofeach component inside the composite. Closed form expressions relating stress-strain state inthe components to the stress-strain state in the composite are derived. Input data are themechanical properties of each component (i.e.: fibres and matrix in case of fibre-reinforcedlaminates) and its distribution inside the composite. This methodology of mixing components plus a decoupling phase strategy (also developed in this work) allow each component to keep unchanged its original constitutive law (isotropic or anisotropic, linear or no-linear) while conditioning the composite global response obtained by assembly of all contributions according to its volumetric participation and stress-strain state. Finite element applications show the capacity of the proposed model to describe the observed behaviour of carbon fibre reinforced laminates in tensile testing. Numerical results are in good agreement with experimental data and approximate the observed response with satisfying accuracy.