A discussion of fracture mechanisms in heterogeneous materials by means of configurational forces in a phase field fracture model

Composite materials are designed in order to combine the favorable properties of their components. For technical applications of these materials the determination of their effective material and fracture mechanical properties is of great interest. The study of fracture of heterogeneous composite materials, which is a necessary first step in order to derive effective fracture mechanical properties, is a difficult topic since macroscopic failure is usually accompanied by various fracture events on the microstructural scale. Finite element implementations of phase field fracture models enable the simulation of complex fracture scenarios as they occur in fracturing of heterogeneous materials. An adaption of the configurational force concept from linear elastic fracture mechanics to the phase field model provides more insight into the mechanisms underlying the evolution of fracture. In this work this ansatz is used to study the interplay between local crack driving forces and the evolution of fracture. Furthermore, the effects of the microstructure on macroscopically measurable quantities like the far field J-integral are analyzed in representative examples comprising continuously modulated as well as layered structures with varying stiffness and varying cracking resistance.