Multi-phase field approach to tensile fracture and compressive crushing in grained heterogeneous materials

The variational approach to brittle fracture is herein extended to deal with the simultaneous interplay of two failure mechanisms affecting grained heterogeneous materials in compression, namely fracture in tension and crushing in compression. The problem is addressed within the context of a multi-phase field variational approach, with two independent damage variables associated to each failure mechanism. The proposed computational method implemented in the open source FEniCS finite element software is applied to 2D mesoscale models of concrete specimens in compression. The predicted trends for specimens with different aspect ratios and different degree of lateral confinement are consistent with experimental results on apparent compressive strength and with typically observed failure patterns.