The operative damage mechanisms in a series of C-matrix composites loaded in tension and shear have been investigated. The composites contained either C fibers or Nicalon fibers, both with and without a carbon coating. The matrix consisted primarily of ex-phenolic carbon with a final carbon layer introduced by chemical vapor infiltration. Some composites have a high fiber/matrix sliding stress. In these composites, failure is characterized by localized fiber pullout. Other composites have a low. Failure of these materials is characterized by stochastic fiber failure with a diffuse fracture surface. The operative damage mechanisms have been identified and used in conjunction with available models to rationalize composite performance in terms of constituent properties (fiber, matrix, interface). The properties emphasized include the inelastic strain, as well as the ultimate tensile and shear strengths.