Design optimization and failure analysis of natural composite sandwich T-joints under pulling load conditions

Abstract

This paper presents a structural analysis of composite sandwich T-joint systems respond to pulling loads. A finite element (FE) model of the T-joint structure was created with four geometrical models, and three different materials were used to compare the design and identify the failure locations. The stress-critical regions were identified within and beneath the Stringers, which are responsible for connecting the base and web panels and transferring loads. The FEA studies showed that T-joint fails due to high shear stress in the stringer, base panel (flange), web, and bolted joint areas. The combination of shear and tensile stress in the adhesive layer between the composite base panel and the stringers lead to failure. Furthermore, incorporating a circular hole in the web panel near the joint resulted in an 11.8 % reduction of failure load. Due to the intricate stress distribution and geometric variations in these joints, premature failure can occur. Therefore, meticulous attention is essential for wing structures at spar joints, especially under extreme load conditions. Despite the complex manufacturing process, the present conventional T-joint design is extremely effective. However, other designs for low-cost manufacturing were proposed and evaluated. The investigation determined that the sandwich structure exhibits a shear stress of 28.88 MPa and von Mises stresses of 57.75 MPa. These values are higher than those observed in design cases 1 and 2. Therefore, design case 3 is suitable for aeronautical applications.