Heterogeneous composite structure has pores, microcracks, internal boundaries of phase division which are the centres of defects origin and development.

Carbon fibres ability to conduct electric current gives an opportunity to use eddy current method for composites, which is good to control metal goods. At the same time there are some specific composite problems which are connected with small value of its specific electric conductivity, inconstancy of conductivity in material volume, presence of complex periodical material structure and its distortions, properties anisotropy, complex defects configuration and considerable surface roughness.

Problems of mechanics of composite materials destruction on polimeric basis, reinforced with carbon fibres, rules of cracks' formation and development in them are considered.

Experimental investigations of module characteristics of surface cracks in carbon fibres composites are carried out. The rules of form changing of module impulses depending upon geometrical values of cracks are defined.

Measurement of crack's depth is made at the range which is not more than eddy current transducer's radius. Range expansion is followed by considerable lowering sensitivity.

The value of crack's opening (width) has the weaker influence on eddy current transducer's characteristics comparing with the influence of depth in optimum range for its measurement. Directions of crack's and transducer's "moving off" from material surface influence coincide in pre-extreme position and are opposite by its active part of addeol impedance in post-extreme position of transducer's holograph for surface defects with small width (less than 100 ). When increasing the opening of crack's influence in post-extreme position is decreased till 0, than it changes its sign and is coincided with "moving off" direction.

Three dimensional model of vertically flaky material, modelling carbon fibre composite in edge position is considered with the crack which crosses the layers and "goes out" to external surface at an indefinite angle. Square frame with harmonious current is used as an transducer. Solution of Helmgotts equation is made by discreet method.

Dependence of active part of added impedance of eddy current transducer from the angle of crack slope to external surface is unmonotonous and maximum. Module impulse itself under the crack slope is unsymmetrical. It is shown in different steepness of impulse slopes.

Amplitudes of active and reactive module impulses reach their maximum at different frequencies: they are lower for active and higher for reactive one by frequency scale.

Transition of medium, which contains high concentration of microcracks (as single vertical layer) to homogeneous medium with equivalent conductivity is made theoretically. The criterion of equivalence is equality of active losses of transducer's field in both cases. Transducer's model as two-wires line, situated simultaneously to boundaries of anomalous layer is considered here. Module characteristics of equivalent conductivity of transducer when coming above defect zone are defined.

Fixed formulas define dependence of equivalent conductivity upon sizes of defect zone, its conductivity and upon material conductivity far beyond its boundaries. Methods of calculation of added impedances and solution of back sums are created. The meaning of conductivity in zone of cracks localization is connected with volume concentration of fibres, which are kept indestructible. It gives an opportunity to evaluate the real value of reinforced coefficient in the sphere of high risk of destruction.