A two-scale failure analysis of composite materials in presence of fiber/matrix crack initiation and propagation

In this work, a numerical multi-scale failure analysis of locally periodic fiber-reinforced composites is carried out. To this end a two-scale finite element continuum approach is proposed, in which coupling between the two scales is obtained by using a unit cell model with evolving microstructure due to mixed-mode crack initiation and propagation at the fiber/matrix interface. Innovative computational techniques have been introduced to perform the localization and homogenization exchanges between the two scales during microstructural damage evolution. The method is able to predict local failure quantities in an arbitrary cell from the results of the macroscopic analysis. These local quantities are then adopted to predict crack initiation by using a coupled stress and energy failure criterion and subsequent propagation. In order to investigate the accuracy of the method in the prediction of failure mechanisms related to the interfacial crack growth at microstructural level, comparisons with a direct analysis adopting a fine-scale modeling of the composite structure, are developed for a 2D fiber-reinforced composite beam with initially undamaged fibers. Numerical calculations demonstrate the effectiveness of the proposed approach and show the accuracy of the proposed method in terms of both macroscopic load–deflection curves and local failure quantities.