Abstract: The mechanical properties of composite long pitch rods are investigated, with special attention to the equivalent stiffness and critical load. Firstly, the equivalent stiffness is calculated by experimental and numerical simulation methods respectively, and the equivalent stiffness results of the two methods have an error of 1.41%. Secondly, based on the three methods of theoretical analysis, numerical simulation and test, the critical load under the existence of initial deflection of the composite long pitch rod is determined. The results show that the error of numerical simulation results relative to the test results is 7.9%, and the error of theoretical calculation results relative to the test results is 14.6%. On this basis, the significant effect of different initial deflections on the critical load is analyzed by numerical simulation, and when the initial deflection is 8.00 mm, the composite long pitch rod buckles at 10.73 kN, which does not meet the use requirements. Finally, the equations for the critical load and initial deflection of the composite long pitch rod are proposed to provide a design basis for manufacturing and maintenance.

Key words: composite pitch rod, equivalent stiffness, stability of compression bar, initial deflection