Creep-like crack propagation in fiber reinforced composites due to damage accumulation proccss

The process of localization and spread of damage ahead of the dominant matrix crack is viewed as a sequence of nucleation and propagation phases both of which may be described by use of the internal damage perameter. This scalar quantity reflects the ratio of the current crack (or pore) density to its saturation, or crltical level. It is shown that the Continuous Damage Mechanics (CDM) approach is useful in modeling a damage field consisting mainly of the fiber breaks ganarated ahead of the matrix crack and clustered around the planw of a prospective fracture, thus forming the so-called ''damage band'' embedded within the stress fleld of the dominant crack. Descrlptlon of thls type of damage applies to the failure process which follows formulation of the ''characteristic damage state'' (CDS) observed in a number of multiphase mterials.