MECHANISMS OF DEFORMATION AND FAILURE IN CARBON-MATRIX COMPOSITES SUBJECT TO TENSILE AND SHEAR LOADING

The operative damage mechanisms in a series of C-matrix composites Loa ded in tension and shear have been investigated, The composites contai ned either C fibers or Nicalon fibers, both with and without a carbon coating, The matrix consisted primarily of ex-phenolic carbon with a f inal carbon layer introduced by chemical vapor infiltration, Some comp osites have a high fiber/matrix sliding stress, tau, In these composit es, failure is characterized by localized fiber pullout. Other composi tes have a low tau, Failure of these materials is characterized by sto chastic fiber failure with a diffuse fracture surface. The operative d amage mechanisms have been identified and used in conjunction with ava ilable models to rationalize composite performance in terms of constit uent properties (fiber, matrix, interface), The properties emphasized include the inelastic strain, as well as the ultimate tensile and shea r strengths.