Large deflections of composite circular springs with extended flat contact surfaces

Large deflections of a range of mid-surface-symmetric, woven composite circular springs with extended flat contact surfaces subject to unidirectional line and surface-loading configurations were studied experimentally and modelled numerically. Finite element analysis was employed to study the load–deflection and strain distribution characteristics. Eighteen woven fibre/epoxy composite circular springs covering a range of different radii and thicknesses were fabricated and tested. Comparison of the results obtained experimentally with the numerical models shows good agreement. The location of the zero-strain point on the spring was found to be related to the loading configuration and the semi-included angle of the composite spring. Correlation curves of the normalized ultimate load versus normalized geometrical parameters of the springs were established successfully. These curves can be used to predict the ultimate load according to the spring’s geometry and mechanical properties.