About calculations of net-tension failure of a bolted joint on the weakened by hole cross-section of composite plate

摘要

Purpose. In order to carry out calculations of net-tension failure of the weakened cross-section of bolted joints with CFRP , it is necessary to estimate the value of the generalized stress concentration factor at the hole. Methodology. Used a method of fin ite- elements and the 3D contact model as much as possible approached to real geometry and conditions of load application. Earlier, the authors created 24 3D models of samples of single-shear two-row bolted joint with CFRP (contact task), in which the structures of CFRP (6 variants) varied, as well as the side gap of bolts with holes (4 values). The magnitude of the contraction force of the packet and the force that stretched the sample were unchanged. Based on the results of calculations, stress distributions are determined and stress concentration coefficients in CFRP plates at the holes (tables, graphs) are calculated. Findings. Based on these results and additional calculations, the following conclusions were reached: -in static strength analysis of net-tension failure of the weakened cross-section of bolted joints with CFRP, as a lower base estimate, one can take the value of the theoretical stress concentration factor ?for a bolt-free hole in an orthotropic material plate, according to the formulas proposed by S.G. Lechnitsky; - to obtain a generalized stress concentration factor ?that takes into account the contact of the hole in the CFRP with the bolt, the value of the lower base estimate of ?must be increased by a factor 2, presumably ?. The adjusted value of the correction factor ? needs to be obtained in additional studies (natural or numerical), which will allow creating a database for values of ?for the topical in the industry options for power bolted joints with composites. Originality. The possible algorithms for estimating the static tensile strength of a weakened cross-section of bolted joints with CFRP are substantiated.