A micromechanical failure model for unidirectional fiber reinforced composites

Results from a newly developed model for failure in unidirectional fiber reinforced composites based on fracture mechanics are presented. The model is based on (i) analysis of branch crack initiation from the tip of an initial microcrack embedded in an anisotropic material, which serves as a model for the fiber reinforced composite and (ii) evaluation of anisotropy in homogenized elastic material properties and fracture toughness. Based on this model, failure envelope, dominant initial flaw orientation and failure mode for unidirectional fiber reinforced composites under a wide range of stress states are predicted. Parametric study provides quantitative evaluation of the effect of various mechanical and physical properties on the failure behavior, and their influence on strength is identified. Results from the current model are compared with those of existing phenomenological models, which show reasonable agreement.