Design and Structural Analysis of Composite Strut for a Lightweight Aircraft

Main landing gears are a critical structural part of an aircraft that support all up weight in static conditions and absorb kinetic energy in a form of impact loads during touchdown. High strength and low weight are critical design considerations for any landing gear strut. During this research, carbon reinforced composite strut was optimally designed such that it undertakes static loads and impact loads of a UAV having GTOW of 1600 kg. CAD models of the designs were developed in CATIA V5R20® and the analysis was carried out in ANSYS Workbench®. Rectangular, circular and elliptical cross-sectional shapes were modeled in ANSYS ACP® with different ply orientation sequences and varying weight distributions from central axis. Least total deformation along with least equivalent stress and aerodynamic drag was considered for the selection of landing gear strut configurational shape. Further design changes in the selected CAD model were incorporated keeping in view the safety factor of the struts. We concluded that 60 preimpregnated carbon reinforced fiber with thermoset polymer matrix having 0.27 mm of thickness for each ply at specified concentration and orientation gave the best results. The orientation of plies was found to be 60 %/ 0°, 30 %/ 45° and 10%/ 90°. Maximum deformation for the final model was 42.154 mm at the joints where the axle was connected with the strut whereas the maximum stress was 712.92 MPa at the joints representing the connection of the landing gears with the fuselage. Drag force for each cross-sectional shape was computed at the takeoff speed of 30 m/s. Drag force for the rectangular cross section was 50.23 N whereas for the circular and elliptical cross section was observed to be 36.837 N and 16.744 N respectively. Hence research concluded that elliptical cross-sectional shape presented least stress distribution and deformation values.