Study on Rigidity and Strength of a New Type of Helical Composite Spring

Though many automotive composite components and parts are being designed and manufactured to reduce the vehicle weight, cylinder helical composite springs are not yet widely used in automobile industry due, in part, to a lack of a fundamental understanding of its somewhat complex behavior. This paper is mainly about the analysis on the stiffness and strength of a type of cylinder helical composite spring whose spring wire has a hollow circular cross section and is made from fiber composite plies with +/- 45 degrees directions from the axis of the spring wire. At first, the manufacturing process of the composite springs is briefly introduced. Then, by combining the equivalent torsional shear modulus of fiber composite laminates with conventional stiffness formula of cylinder helical mental springs, the expression of the rigidity for the composite springs is proposed. At the same time, based on Tsai-Hill failure criterion and classical torsion theories of straight elastic rods, the ultimate compressive load and the maximum compressive displacement are also derived respectively. At last, compared with the results of a series of uniaxial compression tests, these theoretical results are very close to them.