Spring stiffnesses of composite circular springs with extended flat contact surfaces under unidirectional line-loading and surface-loading configurations

Theoretical expressions based on the principle of minimum potential energy are presented which describe the stiffnesses of mid-surface symmetric, woven composite circular springs with extended flat contact surfaces subject to unidirectional line and surface-loading configurations. Three-dimensional finite element analysis has been employed to study the transverse shearing effects. Eighteen woven fibre/epoxy composite circular springs with extended flat contact surfaces in different radii and thicknesses were fabricated and tested. Comparison studies of the results obtained from both the analytical and numerical models are made with experimental data, and the results are found to be satisfactory. The semi-included angle of the flat contact surface is vital parameter to spring stiffnesses of the composite spring.