Senchurov S. The formation of the boundary layer in composite fibers due to the ageing.

A physical model of composite fibers ageing is proposed. The tensions relaxation processes in the covering are found to be the cause of the ageing. It is shown that during the first stage of the ageing the homogeneous boundary layer is formed. The structure of this layer becomes inhomogeneous periodical during the second stage of the ageing. The acoustical method for the verification of the proposed model is developed. For this purpose the theory of sound propagation in composite fibers without boundary layer, with homogeneous boundary layer and with inhomogeneous boundary layer is developed. The corresponding shapes of the acoustical interferograms are calculated. The experimental verification of the proposed model using the developed acoustical method was carried out. The agreement of the experimental data with the parameters of the model is found. The experimental value of the properties of the boundary layer, which is formed during the composite fiber ageing, is obtained.