Composite Belleville Springs

Abstract

Discussed is the development of an analysis for studying the deformation behavior of Belleville springs fabricated of fiber-reinforced composite materials. The springs are subjected to a compressive loading, and owing to the shallow conical geometry of a Belleville spring, snap-though behavior can be exhibited and thus geometric nonlinearities are considered. Considering cost and ease of fabrication, off-the-shelf textile materials along with standard resin transfer molding techniques are strong candidates for the production of composite Belleville springs. However, as off-theshelf textile materials typically employ fibers at fixed angles relative to some reference direction, e.g., 0° /90°, or 0°±45°, or 0°/±60°, using such textiles in a conical geometry results in overall material properties that vary with circumferential direction. This could complicate the response, potentially preventing an axisymmetric response even though the loading is axisymmetric, or at least complicate the analysis of the response. These issues are addressed in the paper, and since modeling of a textile composite Belleville spring involves material properties that vary spatially, in addition to geometric nonlinearities, approximate techniques are used. Specifically, a Rayleigh- Ritz approach is used to approximate the mechanical behavior. Discussed are the material property variations, load-deformation behavior, and strains and stresses as a function of circumferential location. For the particular case considered, a four-layer [(0/90)/(+45/-45)]S glass-epoxy textile laminate, the kinematic response is, for all intents and purposes, axisymmetric. The stress response, however, is not.