Effect of Technological Factors on the Strength of Composite Bolted Joints
The paper presents calculation results for a double lap bolted joint with elements made of polymer composite material (PCM) for different combinations of such processing factors as size of the bolt hole and tightening torque. These calculations are as close to real situation as possible: three-dimensional and finite-element models are used; the task is solved as thermoelastic and contact taking into account power load, amount of clearance and tightness in holes, tightening torque, friction within the joint. PCM was modeled as 3D-orthotropic material. The calculations were made using FEMAP/NX NASTRAN, version 10.2.0. We made calculations according to the plan of a complete factorial experiment: two factors at three levels, nine combinations altogether. Based on calculation results a regression model was developed. It describes the influence of selected processing factors on the volume of maximum equivalent stress by von Mises. The calculation results indicated that processing factors accompanying production of the bolted joint can significantly influence the stress and deformation state of joint elements. Thus, the maximum equivalent stress in calculations changed from 782 to 1146 MPa. So, the difference exceeded 30 %. We can conclude that the method application to design of bolted joint elements with PCM, particularly in aircraft building, is promising.