Dyfuchyn Y. Stress-deformed state and strength of single-lap bolted joints of structural elements of composite materials.

The dissertation is devoted to the scientific substantiation of modifications in the methods of calculation of the static strength of single-lap bolted joints (BJ) of structural elements with carbon fibre reinforced plastic (CFRP). The basis for the substantiation is numerical calculations of the characteristics of the stress-deformed state by the finite element method. The algorithm for the creation of effective finite element models for calculating BJ with CFRP has been developed, which takes into account the main influential factors: the structure of CFRP, the size of lateral bolt/hole gaps, as well as the contact interaction of connection elements, friction between the elements of the BJ. The algorithm is applied to construct a model of a specimen of a single-lap, two-row BJ with CFRP used for fatigue testing. The mixed models for CFRP were applied by layers elastic characteristics in the holes zones and according to the theory of "effective module" on distance from the holes. The decreasing dependence of the bolt/hole contact area size on increasing the size of lateral bolt/hole gaps has been revealed. The algorithm for calculating the values of the forces in bolt sections with account of friction in the BJ as a fraction of the total load is substantiated. It has been revealed that there are significant impact of the structure of the CFRP and the size of the bolt / hole gap on the values of stresses, bending coefficients and stress concentrations coefficients in the BJ. That is why modifications in the criteria of the static strength of single-lap BJ with CFRP were proposed. Key words: composite materials, bolted connections, finite-element approximations, elastic characteristics, stress-deformed state, strength.