A micromechanical failure model for unidirectional fiber reinforced composites

Results from a newly developed model for failure in unidirectional fiber re inforced composites based on fracture mechanics are presented. The model is based on (i) analysis of branch crack initiation from the tip of an initia l microcrack embedded in an anisotropic material, which serves as a model f or the fiber reinforced composite and (ii) evaluation of anisotropy in homo genized elastic material properties and fracture toughness. Based on this m odel, 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 be havior, and their influence on strength is identified. Results from the cur rent model are compared with those of existing phenomenological models, whi ch show reasonable agreement. (C) 2001 Elsevier Science Ltd. All rights res erved.