A numerical study on the free vibration of symmetric cross-ply laminated cylindrical helical springs

The free-vibration problem of (0 degrees/90 degrees/90 degrees/0 degrees) l aminated composite cylindrical helical springs is modeled theoretically as a continuous system. The first-order shear deformation theory is employed i n the mathematical model. The free-vibration equations are solved by the tr ansfer matrix method. A nondimensional parametric study is performed to inv estigate the effects of the number of active coils, the ratio of the diamet er of the cylinder to the thickness of section, the helix pitch angle, and material types on the first six natural frequencies of helical springs with square section and fixed-fixed ends.