Composite structure helical springs with designability of spring constants: Structural design and compression property evaluation

Abstract The static compression capacity of composite helical springs limits their industrial applications. In this study, a new “shell‐core” composite structure helical spring (CSHS) was fabricated using the protrusion molding process. The shell is a metal tube, and the core is a fiber‐reinforced polymer (FRP). By varying the ratio of metal to composite materials, the static and fatigue compressive properties of the composite helical springs were investigated. The results indicate that as the metal shell enveloping the composite core increases, the spring constant of the composite structure helical spring gradually rises from 5.557 to 12.260 N/mm, thereby enhancing the spring's compression performance. The specific stiffness exhibits an initial rapid increase followed by a plateau. Additionally, the finite element method was employed to further analyze the stress evolution of “shell‐core” composite structure helical springs during compression and to predict the spring constant and specific stiffness through curve fitting, which aids in the design of “shell‐core” composite structure helical springs. Highlights Composite structure helical spring (CSHS) improves mechanical properties. Introduced metal has a huge positive effect on the performance of spring. Validated superior spring constant and stability through designed experiments. Achieved designable spring constant via material/structure adjustments.