INFLUENCE OF THE PLATE MATERIAL AND COMPOSITE MATERIAL PLIES STACK-UP SEQUENCE ON THE STRESS CONCENTRATION FACTOR IN THE PLATE WITH A HOLE UNDER TENSILE LOADING

Abstract

At present, there is a tendency to increase percentage of the use of composite materials in the structures of modern aerospace technology. Experience in the operation of critical structures of aerospace engineering made of polymer composite materials has shown that their application instead of structures made of metal alloys provides a reduction in the mass of the structure by up to 30–50%, an increase in the service life by 2–5 times, a decrease in the labor intensity of manufacturing by 20–40% and material consumption - up to 50 %. Application of composite materials in the construction of aircrafts requires the development and application of methods for analysis their static and fatigue strength. The influence of the plate material and composite material plies stack-up sequence on the distribution of normal stresses and the stress concentration factor in the plate with a hole at B/d=6 under uniaxial tension has been studied. It has been shown by calculation that in the case of the orientation of the plies in the same direction with an angle q=0°, the maximum normal stress sх is 1.5 times greater than the corresponding stress value in a plate with a hole made of D16T aluminum alloy. Application of the plies stack-up sequence q [45°/-45°] enables to reduce the level of maximum stresses sх to the level of stresses in the plate with a hole made of D16T alloy. In this case, the area of maximum stresses is shifted from the vertical diametral point along the arc of the hole by an angle of 22.5°. For a woven composite, the level of maximum normal stresses sх is lower than the corresponding stress level for a fiber composite. When using plies stack-up sequence q [45°/-45°], the level of maximum normal stresses sх is lower than the level of the corresponding stresses in the plate with a hole made of D16T alloy. It has been found that, in contrast to the D16T alloy plate, in a plate with a hole at B/d=6, the stress concentration factor could be less or greater than 3, which is explained by the influence of plies stack-up sequence on the stress concentration factor. For a woven composite, when using plies stack-up sequence q [45°/-45°], we obtained the value of the stress concentration coefficient equal to 2.28.