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This paper evaluates the ability of progressive damage analysis (PDA) finite element (FE) models to predict transverse matrix cracks in unidirectional composites. The results of the analyses are compared to closed-form linear elastic fracture mechanics (LEFM) solutions. Matrix cracks in fiber-reinforced composite materials subjected to mode I and mode II loading are studied using continuum damage mechanics and zero-thickness cohesive zone modeling approaches. The FE models used in this study are built parametrically so as to investigate several model input variables and the limits associated with matching the upperbound LEFM solutions. Specifically, the sensitivity of the PDA FE model results to changes in strength and element size are investigated.

A derivation of the required release pressure for use in a finite element implementation of decohesive failure simulation to model linear elastic fracture mechanics in an orthotropic material is presented. Studies to illustrate the sensitivity of the predicted results due to mesh size and release pressure were performed. The release pressure needs to be kept within certain bounds, which are mesh dependent, for reliable predictions. Nomenclature a = half crack length c = critical (subscript) C = parameter d = displacement E = Young's modulus F = force G = shear modulus G c = critical energy release rate L = length r = release (subscript) w = width (into the page) X = static strength x = Cartesian coordinate y = Cartesian coordinate  = stress  = strain  = Poisson's ratio  = value at infinity (subscript) 1

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