Localization due to damage in fiber-reinforced composites

International audienceFiber pull-out is one of the fracture features of fiber-reinforced ceramic matrix composites. The onset of this mechanism is predicted by using Continuum Damage Mechanics, and corresponds to a localization of the deformations. Alter deriving two damage models from a uniaxial bundle approach, different configurations are analysed through analytical and numerical (F.E. calculations) methods. For one model some very simple criteria can be derived, whereas for the second one none of these criteria can be derived and the general criterion of localization has to be used

Tensile and flexural ultimate strength of fiber-reinforced ceramic-matrix composites

International audienceA constitutive equation has been derived for fiber reinforced ceramic-matrix composites, based on fiber breakage and distributed fiber pull-out. Length-dependent and length-independent regimes, governed by the size of the specimen, are differentiated, The constitutive equation is used to predict the ultimate strength of fiber-reinforced ceramic-matrix composites subjected to tensile and flexural loadings

Continuum Description of Damage in Ceramic-Matrix Composites

International audienceA constitutive law is proposed for Ceramic-Matrix Composites which models matrix-cracking, interface debonding and sliding, fiber-breakage, and fiber pull-out. These different mechanisms induce loss of stiffness, inelastic strains, hysteresis loops, and crack closure. The features are analyzed within the framework of Continuum Damage Mechanics by the introduction of physical internal variables identified previously in material science investigations. The procedure is applied to a SiC/SiC [0/90] laminate composite using the results of pure tension tests of two laminate orientations. Each test involves a series of loading and unloading sequences. In order to verify the material description the behavior of an Iosipescu shear test is predicted using a Finite Element calculation and the results are compared with experiment

Fiber Breakage and Fiber Pull-Out of Fiber-Reinforced Ceramic-Matrix Composites

International audienceFiber breakage and fiber pull-out induce loss of stiffness, anelastic strains, hysteresis loops, and crack closure. Ultimate strength properties of fiber-reinforced composites are derived and compared with results related to localization. These features are analyzed in the framework of continuum mechanics through the introduction of internal variables. Three models which are progressively more faithful to the micromechanical analysis are studied. They provide guidance on the choice of the relevant internal variables to model the mechanical behavior of unidirectional fiber-reinforced composites